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321 Cards in this Set
- Front
- Back
nonspecific defenses
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skin, mucous, cilia, acid pH, lysozyme
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inflammation
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vascular changes, activation of leukocytes (mast cells, phagocytes, platelets), histamine, arachidonic acid
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C-reactive protein
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recognizes polysaccharide capsule of pneumococcus
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innate immunity
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non-clonal, non-specific, constitutive monitoring for known pathogen molecules; rapid response, fixed, limited in specificity, constant during response
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adaptive immunity
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altered response in host to a second encounter to a pathogen (resistance); slow response, variable activity, highly specific, improves during response
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humoral immunity
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adaptive immunity that can be transferred to another individual by transferring serum;
mediated by antibodies |
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cellular immunity
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adaptive immunity that can only be transferred by transferring viable lymphocytes;
mediated by T lymphocytes and their products |
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functions of the adaptive immune system
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1. recognition-- specific and has memory
2. amplification-- cell division and enz cascades 3. Regulation 4. Effector mechanisms-- how the pathogen is actually eliminated |
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antigens
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recognized by T and B lymphocytes via antigen receptors on surface; binding activated the lymphocyte and complement cascade
in B lymphocytes, the receptors are actually membrane anchored antibodies |
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effectors cells (B and T)
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effector B cells: plasma cells that secrete antibodies
effector T cells: helper T cells (secrete cytokines) and cytotoxic T cells |
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phagocytic cells
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monocytes, macrophages, neutrophils, eosinophyiles, PMN leukocytes, immature dendritic cells
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basophil v. mast cell
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basophil- circulate in blood stream
mast cells- found in tissue only |
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monocytes v. macrophage
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monocyte-- circulate in blood stream
macrophage-- found in tissue only |
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immunoglobulins (aka antibody)
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heterogenous group of glycoproteins; key component of humoral immunity; found in circulation and on B-lymphocyte surface
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antibody structure
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4 polypeptide chain--2 heavy and 2 light linked via disulfide bonds; usually symmetrical
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Light chain of antibodies
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kappa or lamda;
have two domains, one is variable (the constant domain differentiates kappa from lamda) both types equally bind heavy chains, but conc. of kappa 2x more than lamda in circulation note: any one antibody will have the same two types of light chains- both will be lamda or kappa |
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Heavy chain of antibodies
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alpha, delta, gamma, epsilon, mu;
have 4-5 domains, one variable domain (the 5 types differ in their constant domain) |
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hinge region
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papain, a protease enz, cleaves the antibody into 2 Fab fragments and a Fc fragment
pepsin, a protease enz, cleaves the antibody into a F(ab')2 fragment and a degraded Fc fragment (F(ab')2=2 Fab linked together) |
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Fab
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made of light chain and the variable and first constant domain of the heavy chain; has one antigen-binding site
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Fc
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has the carboxy-terminal part of the heavy chains; can activate cascades after antigen binding
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IgG
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75% of serum Ig: 4 subclasses
IgG1>>IgG2>IgG3>IgG4; monomeric, major antibody of secondary immune response; ONLY antibody to cross placenta, subclasses 1-3 activate complements; they are opsonins and ADCC; IgG4 unique- can have asymmetry by exchanging one heavy and one light chain |
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ADCC
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antibody dependent cellular cytotoxicity-- effector mechanism of cell-mediated immunity
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IgM
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10% of serum Ig,
pentameric (5) via J chain (a glycoprotein), mu heavy chains have extra domain; Major antibody formed in PRIMARY immune response, most efficient complement activator; found on B lymphocytes (as a monomer) |
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IgA
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predominant antibody of seromucous secretions;
15-20% serum Ig can be monmeric or in dimer via J chain; 3 subclasses: IgA1 and IgA2, has a secretory signaling portion which allows it to be sercreted and protects it from being digested |
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IgD
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<1% serum Ig
monomer, predominant Ig on B lymphocytes along with IgM, can also activate B cells like IgM |
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IgE
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<.004% of serum Ig,
epsilon heavy chain has extra domain, binds strongly to Fc receptors on basophils and mast cells, mediates immediate hypersensitivity rxns |
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memory B lymphocytes
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have IgG, IgA, IgE on surface as antigen receptors ( all as membrane bound and monomeric)
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Isotype
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defines structural difference in the constant region that distinguish class and subclasses (each has its own genes)
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Allotype
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defines small structural variations in the constant regions of an Ig of the same isotype in the same species
exihbit polymorphisms (mendelian inheritance) |
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Idiotype
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determined by structural differences w/i variable domains -- unique to each antibody depending on what antigen it binds
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Myeloma proteins
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Ig synthesized from a single clone of a malignant plasma cell---> MONOCLONAL
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Bence-Jones proteins
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free light chains; found in urine of pt w/ multiple myeloma
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immunogenicity
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capacity of a substance to induce an immune response (humoral, cellular, or both)
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antigen
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substances that react specifically with the immune system, namely antibodies;
can be proteins, polysaccharides, lipids, nucleoproteins, anything |
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criteria for immunogenicity
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only foreign molecules, minimal size needed, rxn increases with increase in molecule complexity
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antigenic determinants/ epitopes
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portions of antigenic molecule that reacts with antibodies
usually 5-7 a.a. or monosaccharides; hydrophillic immunodominant epitopes- determinants that most people respond to |
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haptens
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small molecules, that are NOT immunogenic but can bind to antibodies;
always univalent; can become immunogenic if bound to a carrier protein e.g. dintorphenol, DNP |
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Antigen Binding Site
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in variable region of Ig, but variablity in variable domain not uniform-- hypervariable regions have more variability
light chains have 3 hypervariable domains and heavy chains have 3-4; hypervariable region of heavy and light chain together from the antigen binding site |
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Complementarity-determining region
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same as antigen binding region,
antigen binds strongly to the antibody; close fit |
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antibody specificity
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usually antibodies bind very specifically to the antigent hat induced their formation,
cross-reactivity- antibody binds to another antigen with similar epitope, but usually less tightly |
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antigen-antibody binding
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rxn b/ antibody and antigen is reversible, but slow and irreversible under normal conditions
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affinity
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measure of stregnth of interaction b/w a single antigen epitope and a single antigen binding site (Fab) of an Ig
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avidity
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measure of stregnth of the binding b/w a multivalent antibody and multivalent antigen; IgG, IgD, IgE have two sies, IgA has four and IgM has ten sites
avidity is greater than the simple sum of the indiviual affinities |
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agglutination
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antibody interaction with particulate antigens (intact cells)
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precipate of antibody
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binding of antibody to soluble antigens may cuase precipitate.
with increasing amount of antigen the amount of precipitate increases |
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antibody excess
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concentration of antibody excedes that of the antigen; hence excess antibody even with all antigen bound
|
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antigen excess
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concentration of antigen is excess than that of antibody, means every one antibody molecules will find bind and crosslink two antigen molecules
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equivalence
|
concentration of antibody about the same as the concentration of antigen
|
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Immune complexes
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antigen-antibody complexes;
cleared from blood by phagocytic cells via reconginition of Fc poritons of Ig. Fc can also activate completment |
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Therapeutic antibodies
|
used of monoclonal antibodies against defined antigenic targets;
initially mouse Ig used but they were immunogenic so now humanized monoclonal Ig used (has constant domains from human IgG--chimeric) |
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T cell antigen receptor (TCR)
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recognizes only peptide antigens, presented in peptide binding groove of MHC class I molecule or MHC Class II molecule
|
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Cellular Differentiation (CD)
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molecules expressed on T-cell surfaces during maturation and crucial to selection of T cell that will reach maturity and in subsquent antigen recognition;
eg. CD3, CD4, CD8 |
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TCR chains
|
T cell receptors are two chain molecules,
two pair types: alpha & beta (95%) or gamma & delta (rare); contains domain structure similar to Fab (variable, hypervariable and constant regions)--each T cell recognizes ONE antigenic determinant, has ONE antigen receptor specificity w/ unique idiotype- ONLY 1 alpha variable region on each αβ T cell with only 1 beta chain variable region! |
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CD functions
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differentiate one cell type from another
differentiate one stage of cell proliferation from an earlier or later stage |
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CD 19 and CD 21
|
identifies cells as B lymphocytes
|
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CD 3
|
identifies a cell as T cell
has 5 chains: gamma, delta, epsilon, and zeta chains(x2) |
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TCR variability
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variable region of chain undergoes gene rearrangement,
|
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T- cell v. antibody
|
antibodies bind free, soluble, UNPROCESSED antigen;
TCR can't recognize free, unprocessed antigens, so T cell epitopes mainly hydrophobic and linear determinants (also no hinge region) |
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CD 3 function
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undergoes conformational change when the TCR binds to the MHC-antigentic peptide complex and causes activation fo intracellular protein tyrosine kinase-->activates the T cell
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B cell antigen receptor (antibody) v.
TCR |
B cell: has BOTH IgM and IgD which can be secreted, recongize free, unprocessed antigens
associated w/: Igα, Igβ, CD19, CD20, CD21 TCR: has only one type of receptor αβ OR gamma/delta at a time, no secretion; recongizes antigen if bound to MHC molecule only! associated w/ CD3 |
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Major Histocompatibility Complex (MHC) molecules
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refers to genes, whose products are central to communication in the immune system via surface glycoproteins
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Human Leukocyte Antigens (HLA)
|
same as MHC;
found on Chromosome 6, 3 classes (in order from centromere towards the telomere): Class II: HLA-DP, HLA-DQ, HLA-DR Class III: Complement C2, C4, B, TNFα & β Class I: HLA-B, HLA-C, HLA-A |
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Class III MHC
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encode secreted (plasma) proteins, dont participate in direct antigen recognition
include tumor necrosis factors and complement proteins |
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Class I MHC
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molecules found all nucleated cells, all 3 have similar structure:
2 chains: heavy α chain- transmembrane anchor with peptide binding groove near the aminoterminal light β chaine called β2-microglobin (gene on chromosome 15), functions to transport MHC class I molecule with a peptide bound to the cell surface, to the cell surface |
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function of Class I MHC molecules
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to act as TARGET for the elimnation of abnormal host cells:
cells taht are infected w/ intracellular agent or mutated or transformed (oncogenic) |
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Class I MHC mechanism
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carry out function by binding to peptides being actively synthesized by the host cell, proteins degraded and expressed on cell surface bound to the MHC molecule
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Cytotoxic T lymphocytes
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recognize abnormal peptides on Class I molecules, triggers release of cytotoxic molecules, killing infected cell
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Class II MHC tissue distribution
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Monocytes, macrophages, B Lymphocytes, Dendritic Cells, Langehans cells (skin), activated T lymphocytes, activated endothelial cells
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fourth Class II MHC molecule
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HLA-DM
found only within endosomal compartments, plays role in transferring peptides to the other MHC class II molecules |
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Class II MHC function
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present exogenous foriegn peptides to HELPER T lymphocytes
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Class II MHC mechanism
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proteins from outseide non-specifically internalized by endocytosis, degraded, and allowed to bind to MHC class II molecules in the endosome; MHC Class II - peptide complex moved to cell surface where helper T cells can recognize them
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Helper T cells and Class II MHC
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Helper T cell have antigen receptors that can ONLY recognize peptides bound to MHC Class II molecules
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MHC Class II post translation processing
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intially made with a 3rd chain- the invariant chain
at endosome, invariant chain degraded and CLIP remant peptide released when exogenous peptide binds to MHC class II molecule |
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MCH Class I v. Class II
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Class I: all nucleated cells, peptides from endogenous, elimination of infected cells, has β2-microglobulin,
recognized by cytotoxic T cell (CD8) Class II: only on select cells, processed exogenous peptides, presentation of foriegn antigen to helper T cell, has invariant chain recognized by Helper T cell (CD4) |
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TCR-antigen-MHC interaction
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TCR recognize the antigen-MHC complex as a whole;
CD4 and CD8 stabilize this interaction, CD3 works closely to transduce the signal upon binding |
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Purpose of lymphoid organs
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optimize the recognition aspect of the immune system
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immunocompetence
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primary lympoid organs are anatomical locations where lymphocytes develop immunocompetence-- the ability to specificallly recognize foreign antigen, but are not exposed to foreign antigen yet
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Bone Marrow
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primary lymphoid organ for lymphoid precursors and hematopoesis,
cytokines IL-7 and IL-3 help maturation process B cell mature in bone morrow |
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Thymus
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primary lymphoid organ,
T cells mature in thymus |
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Secondary lymphoid tissue
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immunocompetent cells, capable of recognizing and responding to antigen, migrate to these secondary organs to await their specific antigen
e.g. tonsils,lymph nodes, spleen, lamina propria, peyer's patches |
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Thymus structure
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bilobed organ, divided into lobules, with an outer cortex and inner medulla;
T cells migrate in from blood and move towards the medulla as they mature |
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Thymic Function
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secretion of thymic hormones (5 identified in T cell differentiation)
education: select T cells based on ability to distinguish self from non-self |
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Positive Selection of T cell
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developing T cells that recognize self MHC molecules sufficiently, get positive selection-- a signal to continue dividing
eventually end up in secondary lymphoid organs |
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Failure to positive selection
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developing T cells that don't recognize self MHC molecules so don't get signal to die... end up dying in thymus
|
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Negative selection of T cell
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developing T cells that bind to self MHC molecules too well, are induced to commit suicide;
if not removed, they may react to self MHC causing autoimmune diesease |
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Lymph Nodes structure
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have affarent lymph vessel and lymph flows towards medulla and out efferent lymph vessel;
B cells in folicles/germinal center T cells in paracortex |
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Lymph node function
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allows the B cells and T cells exposure to a sample of antigens present in the system;
if B cell activated then follical produces a germinal center, differentiation into plasma cells, and Ig secretion node also allows for immunological memory via B and T memory cells |
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Spleen function
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samples antigens in systematic blood circulation
B cells found in marginal zone T cells found in periarteriolar lymphoid sheath |
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MALT
Mucosa Associated Lymphoid Tissue |
lymphoid tissue throughout sub-mucosa and lamina propria;
eg Peyer's patches |
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Lymph circulation
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into tissue out of capilllary, into lymphatic vessels, into lymph nodes, into efferent vessels, into thoracic duct, into systemic blood, through spleen..... repeat
|
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Prethymic stage
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bone marrow precursors for T lymphocyte development,
express TdT |
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T lymphocyte development
Stage I |
in thymic cortex, cells still immature,
express CD2 - begin rearranging TCR β chain cells still not responsive to antigen yet |
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T lymphocyte development
Stage II |
intermediate(common) thymocyte
express CD3 on surface along with TCR TRC α chain rearranged CD4 and CD8 BOTH expressed |
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T lymphocyte development
Stage III |
in thymic medulla
cells become mature thymocytes.. CD4 and CD8 now distinct subsets (only have one or the other) committed to helper or cytotoxic function |
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γ-δ T cell
|
T cells first try rearranging δγ chains., if not successful then move onto αβ chains
γδ dont usually express CD4 and CD8, represent only 5% have very little variability |
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T cell education
|
T cells interact with thymic epithelial cells and w/ dendritic cells
self reactive T cells eliminated or inactivated here; foreign antigens not present |
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delveloping T cell CD expression
|
early in development, both CD4 and CD8 coexpressed
|
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CD4 T cell
|
if TCR of T cell has high affinity for MHC class II molecules then CD4 retained and CD8 lost
they become helper T cells enter circulation, and wait for antigen ALL helper T cells express CD3, CD4, and TCR on surface |
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naive helper TH0 cell
|
when antigen recongize they differentiate into TH1 or TH2,
but undifferentiated TH0 cells can secrete cytokine products of both TH1 and TH2 |
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TH1 cells
|
secrete interleukin-2 (IL-2) and interferon-γ (INF-γ)
which stimulate cell-mediated immunity |
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TH2 cells
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secrete IL-4, IL-5, IL-6, and IL-10 which play major role in B lymphocyte differentiation and antibody production
|
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CD8 T cell
|
if TCR has affinity for MHC class I molecules then CD8 retained and CD4 eliminated from cell surface-- becomes a cytotoxic T cell
migrate to periphery and lymphoid organs, wait for antigen activated by TH1 cytokines to become cytotoxic effector cells |
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CD3
|
expressed on all T cells
TCR associated signal transduction molecules |
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CD2
|
expressed on all T cells
allows adherence to other cells and bint to LFA-3 |
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CD40 LIGAND
|
expressed on activated HELPER T cells
binds to CD40 on B cells, essential for Ab isotype swithing |
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CD28
|
expressed on Helper T cells and most CD8+ T cells
costimulatory molecule needed for T cell activation; binds B7.1 and B7.2 |
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CD4
|
expressed on HELPER T cells
interact with MHC Class II molecules |
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CD8
|
expressed on CYTOTOXIC T cells
interact with MHC Class I molecules |
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Bursa
|
B cells devlop in bursa of fabricius in birds
in humans, they develop in the fetal liver and then in the bone marrow |
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Initial stage of B cell differentiation
Pre B cell |
rearrangement of heavy chain variable region genes (V, D, J) at randm to begin making a mu chain
the PRE B cell has prescence of cytoplasmic mu chains |
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Immature B cell
|
the light chain vairable region rearranges (V, J, and kappa or lamda) to make the light chain
the cell expresses IgM on its surface; it IS anitgen-responsive |
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Mature B cell
|
express surface IgM and surface IgD (sometimes IgG too)
* NO antigen required to mature* antigen binding causes B cell activation, cell division and differentiation to plasma cells plasma cells secrete large amts of Ig |
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B cells v. Plasma cells
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B cells express Ig on cell surface, they do NOT secrete them
Plasma cells secrete Ig but do NOT express on cell surface |
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CD19
|
signal transduction
used clinically to enumerate B cells |
|
CD20
|
signal transduction
|
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CD21
|
complement receptor type 2 (CR2), which binds to C3d
also receptor for EBVirus |
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CD40
|
costimulatory molecule required for memory and class switch signals from T cells
|
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B cells and MHC
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ALL B cells express MHC Class II molecules, essential in their interaction w/ helper T cells
|
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Tdt
|
marker on pro-B cells and pre-B cell that gives them added variability to thier heavy chains
|
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Pre-cursor B cell
|
germ line (no rearrangement yet) no Ig
in bone marrow |
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Pre-B cell
|
only heavy chain rearranged,
heavy chain of IgM in cytoplasm only antigen unresponsive still |
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Immature B cell
|
Heavy AND light chains rearranged;
only IgM on surface, antigen responsponsive BUT easily tolerized (turned-off) |
|
Mature B cell
|
heavy and light chains rearranged,
BOTH IgM and IgD coexpressed on surface antigen responsive short lived difficult to tolerize |
|
Memory B cells
|
NEED T CELL cooperativity
constant region heavy chain gene rearranged--> class switch IgG(1,2,3,or4), or IgA or IgE on surface, but only ONE type on whole cell long lived -- 10+ years |
|
Plasma Cell
|
rapid synthesis and secretion of only ONE Ig class
lasts 4-6 weeks |
|
Memory B cells
|
NEED T CELL cooperativity
constant region heavy chain gene rearranged--> class switch IgG(1,2,3,or4), or IgA or IgE on surface, but only ONE type on whole cell long lived -- 10+ years |
|
Plasma Cell
|
rapid synthesis and secretion of only ONE Ig class
lasts 4-6 weeks |
|
antibodies needed?
|
10^7 to 10^9 different antibody specificites would be enough to recognize every concievable antigenic structures
our bodies make about 10^8 different antibodies |
|
how can a limited amt of DNA possibly encode for enough variation that all antigenic molecules can be recognized?
|
- Limited size of the antigenic derterminant
- cross reactivitybetween antigens limits the requirement of novel variations - we inherit multiple V region gene segments that encode some specificities; during Ig synth one randomly chosen for the light chain and one for the heavy chain - mutations common since B cells divide rapidly (not applicable to T cell TCR) - recombination of variable region gene segments; 3 genes make up the expressed mRNA, so many combinations possible - recombination inaccuracies introduce a lot of variability; TdT enz active (inserts bases randomly) - random assortment of combinations of light and heavy chain allows for variability |
|
inheriting V region gene segments
|
germ line genes; encode for vaiable domains of heavy chains, light chains, and TCR α, β, γ, δ chains
for every Ig there are 100-300 such genes for each chain during B cell development, ONE heavy chain set and One light chain set RANDOMLY chosen |
|
Recombination of variable region gene segments
|
genes coding for variable domains split into a group of 100-300 V gene segments
they encode for first 95 a.a. of the 110 that make up the domain last 15 a.a. found in a linked set of DNA segments further down on the chromosome for light chains, 1 of 4 possible J gene segments are randomly chosen and expressed with a randomly chosen V region sequence for heavy chain there is a third segment (in addition to the V and J segments mentioned above), the D segment (D=diversity) there are 10-20 such D segments that code only 1-2 a.a. each combination VDJ combination gives a different structure to the hypervariable region of the Ig |
|
terminal deoxyribonucleotidyl transferase (TdT)
|
introduces recombination inaccuracies
an enz that randomly inserts aNy base pairs (N-region additions) when heavy chains undergoing recombination TdT not active when light chains rearrange later also get inaccuracies when coding sequences are fused at splice junctions (extra base pairs) |
|
rearrangement rules
|
if all the recombination and rearranging produces a functional Ig, then B cell expresses the IgM monomer on its surface
meanwhile other alleles supressed and rearrangement mechanism halted |
|
allelic exclusion
|
when a functional gene product made, all other rearrangement and expression of the other allele (on homologous chromosomes) SHUT OFF
so each B cell will have only ONE heavy chain variable domain and only ONE light chain variable domain also applies to TCR chains: only ONE α chain and ONE β chain expressed OR ONE δ and ONE γ chain |
|
RNA splicing of Ig Genes
|
alternative RNA splicing determines whether the Ig will be secreted or expressed anchored to the cell surface
also determines whether the B cell will express surface IgM, IgD, or BOTH |
|
Class Switching
|
during antibody response:
Helper T cell (TH2) releases cytokine signals: IL-4, IL-5, IL-6, IL-10, and surfase CD40 --> signals B cell to switch class done by rearranging DNA of constant region of the heavy chain (loop formed b/w homologus SWITCH regions...and loop degraded), information deleted this switches b/w IgM and IgG (any subclass 1-4), IgA (1 or 2), or IgE ONE WAY SWITCH!!! no reversion does NOT effect the variable region so specificity of Ig remains same, regardless of isotype |
|
Lag phase
|
the time between the intitail challenge with antigen and the appearance of the first detectable antibody in the serum
varies with dose and solubility of antigen, route of injection, prescence of adjuvant, species, and assay sensitivity to the antibody |
|
Lag Phase events
|
antigen-specific lymphocytes are increasing in number--> increase in amount of antibodies ( a function of antibody synthesis and degradation)
note: antibody-antigen complexes cleared from blood more quickly than free antibody |
|
Log phase
|
a LOGarithmic increase in serum specific antibody levels (primarily a result of logrithmic inc in antibody secreting cells)
|
|
Plateu phase
|
antibody levels in serum remain relatively stable..no increase, no decrease
balance of synthesis and degradation |
|
Decline phase
|
specific antibody levels decline to VERy low, undectable levels
Ig degradation continues without continued synthesis |
|
Phases of primary response
|
Lag, Log, Plateau, Decline
|
|
Secondary response
|
More antibody produced (faster and greater amounts)
Lag phase is always shorter Less antigen required to trigger full immune response |
|
Primary v. secondary
response |
In primary: IgM alwasy appear first
In secondary: IgG is predominant (IgA predominant if secondary response in mucus) |
|
Affinity Maturation
|
Ig affinity changes during immune response
all B cells stimulated to produce antibodies even though most antibodies will be uselss, so AVERAGE antibody affinity very low how as antigen levels drop later, only B cells with highest affinity for antigen will remains stimulated, and so only high affinity antibodies will be produced increase in AVERAGE Ig affinity with time occurs for IgG antibody |
|
Clone
|
individual lymphocyte (B cell or T cell) and its progeny
antigenic specificity of an individual clone is maintained during mitosis |
|
Clone wars
|
The Clone Wars began during the Separatist Crisis when thousands of star systems seceded from the Galactic Republic to form the Confederacy of Independent Systems (CIS). The first battle occurs on the CIS planet Geonosis where the Republic's new clone army, led by Jedi generals, combats the Separatists' battle droids. War quickly spreads across the galaxy and eventually reaches the Republic's capital, Coruscant. The Clone Wars end shortly after the Great Jedi Purge with the Separatist Massacre on Mustafar and the establishment of the Galactic Empire. The events causing the war and those leading to its conclusion are orchestrated by the Republic's chief executive, Supreme Chancellor Palpatine.[2]
jp haha... i had to... |
|
monospecific, polyclonal antibody response
|
a signle antigen can activate multiple B cells with varying specificities (b/c cross reactivity)
|
|
specificity (revisited)
|
B and T cells produced generate specific responses to almost infinite anigenic structures
One B cell = ONE Ig specificity One T cell = ONE TCR specificity --> means each cell will recognize one and only one antigen ALL specificities ever needed made all the time by random selection fo hypervariable region |
|
clonal selection
|
antigen "selects" the cell with a complementary receptor, binds to it, and initiates cell division and differentiation in the cell
|
|
Mature B cell lifetime
|
(virgin B cell)
live for only a few days UNLESS activated by encounter with a recognized antigen |
|
Antigen-Stimulated B cell
|
undergos several rounds of mitosis--> generates CLONES
all have same antigen specificity if antigen continues to be present to simulate them, then differentiation into PLASMA CELLS |
|
Plasma cell lifetime
|
non-dividing,
live about 4-6 weeks synthesize enormous amounts of Ig with identical structures, isotype, and specificity (idiotype) |
|
Memory B cell lifetime
|
very long lived, about 10 years
will switch classes during differentiation in response to cytokine signals but specificity remains unchanged (unless mutation occur during cell divisions) |
|
Primary Response
Lag Phase cellular response |
no antibody detected in serum;
Macrophages: trap, process, and present antigen T helper cell activation T-B cell interaction B cell: activation, clonal expansion, differentiation to Plasma cells |
|
Primary Response
Log Phase Cellular response |
Rapid increase in serum Ig levels;
antigen-stimulated increase in B cell number; isotype switching differentiation into Plasma cells |
|
Primary Response
Plateau Phase Cellular Response |
constant level of Ig;
Depletion of antigen; no further clonal expansion no further differentiation to Plasma cells continued Ig secretion by Plasma cells |
|
Primary Response
Decline phase Cellular response |
Ig levels drop;
Plasma cells reach end of life span, die but are NOT replaced due to lack of antigen stimulation B and T cells have begun to differentiate into memory cells |
|
Secondary Response
Lag Phase (SHORT!) Cellular response |
little Ig amt detected in serum;
Macrophage: trap, process, present antigen Memory T helper cell activation T-B Cell interaction Memory B cell activation and clonal expansion and RAPID differentiation to Plasma cells |
|
Secondary Response
Log phase ceullular response |
VERY rapid increase in serum Ig levels;
antigen-stimulated increase in memory B cell number and differentiation into Plasma cells |
|
Secondary Phase
Plateau phase Cellular response |
near constant (but higher than primary) Ig levels in serum;
Depletion of antigen, no further clonal expansion or differentiation into plasma cells continued Ig secretion by plasma cells |
|
Secondary Response
Decline phase cellular response |
Ig levels drop;
Plasma cells reach end of life span, but not replaced b/c lack of antigen stimulation Memory B and T cells renewed |
|
Cell Mediated Immunity
(CMI) |
immune responses can be adoptively transferred from one animal to another by transferring CELLS (lymphocytes);
serum transfusion not enough |
|
Humoral Immunity
|
immune response mediated by antibodies (Ig) adn so transferring Ig-containing serum, transfers immunity
|
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CMI v. Humoral immunity
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antibodies recognize free state antigens (extracellular),
CMI involved in elination of abnormal host tissues and INTRAcellular pathogen ex: T cells recognize antigens ONLY when presented by MHC on the surface of cells |
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Specificity in CMI
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specificity provided by T lymphocytes
MHC molecules present antigens on cell surface MHC class II molecules present to CD4+ helper T cells (TH) MHC class I molecules present to CD8+ cytotoxic T cells (CTL) activated CTL effector cells are antigen specific |
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Delayed Type Hyersensitivity
(DTH) |
response initatied by teh presentation of antigen by an antigen presentign cell (APC) to a CD4+ T lymphocyte
once activated, DTH non-specific |
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DTH
activation of CD4+ cell |
activation is antigen specific adn MHC class II RESTRICTED!!!
leads to proliferation of the CD4+ cells, expression of CD40 ligand, and production of effector cell that secrete TH1 cytokines, which induce inflammatory response and activate macrophages |
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TH1 cytokines
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includes IL-2, INF-β, INF-γ, hematopoetic factors and cytokines
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DTH
macrophage activation |
differentiate to activated state upon exposure to INF-γ;
have incresease expression fo MHC class I and Class II molecules, TNF receptors, and CD40 on surface activated macrophages more efficient at killing (ingesting organisms) than resting (resident) macrophages; can also kill some tumor cells and virus infected cells, BUT killing mechanisms are NOT antigen specific and NOT MHC restricted! |
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Activated Macrophage cytokine secretions
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secrete cytokines including:
TNF-α, IL-1, IL-6, chemokines, PGE2, reactive oxygen metabolites, and enz that cause nonspecific tissue damage |
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Macrophage killing mechanism
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when they encounter a particular antigen, develop EPITHELIOID cells, then fuse into Mmultinucleated Giant Cells, which wall off antigens that resist killing,
final stage is formation of GRANULOMA, characteristic of chronic CMI rxns |
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INF-γ and CD40 ligand on activated DTH
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activated macrophage to destroy engulfed bacteria
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Fas ligand or LT on activated DTH
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kills chronicall infected macrophages, releasing bacteria to be destroyed by healthy macrophages
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IL-2 on activated DTH
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induces T cell proliferation, increasing number of effector T cells
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IL-3 + GM-CSF on activated DTH
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induces macrophage differentiation in the bone marrow
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TNF-α + LT on DHT
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activates endothelium to induce macrophage adhesion and exit from blood vessels at site of infection
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CXCL2 on activated DTH
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causes macrophages to accumulate at site of infection
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CTL mediated CMI
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CD8+ cytotoxic T cells are antigen specific and MHC restricted
in primary response, need CD4+ helper T cell (TH1) to differentiate into effector killer cells, but not needed in secondary response TCR respond to antigen presented by MHC class I on cell surface and resond by elimnating infected, nucleated cells |
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CTL activation and TH1 role
CD8+ and CD4+ T cells |
fully functional differentiated CTL recognizes a target cell with the same MHC class I antigen complex;
cell-cell contact (conjugate formation) lead to target cell death; CTL and TH1 maybe activated by different APCs or same APC, BUT memory CD8+ cells can be fully activated W/O CD4+ help |
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Cytotoxic T cell killing mechanism
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secrete pore-forming molecules (perforin) from granules when cell-cell contact made; perforin polymerizes int a channel on the target cell membrane;
also contains granules with esterases and may release lymphotoxins (LT , aka TNF-β), and Fas ligand molecule results in target cell death by lysis apoptosis |
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CD8 T cell effector molecules
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cytoTOXINS: perforin, ganzymes, granulysin
cytoKINES: INF-γ, LT |
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CD4 (TH1) T cell effector molecules
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CytoKINES:
INF-γ, GM-CSF, TNF-α, LT, IL-3 |
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CD4 (TH2) T cell effector molecules
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cytoKINES:
IL-4, IL-5, IL-10, IL-13, TGF-β |
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Natural Killer Cells (NK)
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a subset of lymphocytes found in blood adn lymphoid tissues
responsible for earliest response to infection and for role in controlling viral infections before effective CTL cell response generated |
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NK cell maturation
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arise from lymphoid lineage of bone marrow cells, differentiate directly into the blood circulation;
don't require further maturation like T cells comprise 5-20% of peripheral blood lymphocytes differentiate from T cells, monocytes, adn B cell by unique CD antigens |
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targets of NK cells
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target specificity broader than CTL BUT not random,
can kill tumor cells and some virus-infected cells, and will NOT kill normal, uninfected cells |
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NK cell CD antigens
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CD16, CD57, CD56, CD8, CD2, CD11a, CD11b, CD11c, CD18
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T cell CD antigen
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TCR/CD3, CD2, CD4, CD8, CD57, CD56, CD11a, CD18
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Monocyte CD antigens
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CD14, CD16, CD11a, CD11b, CD11c, CD18
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B cell CD antigens
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surface Ig, CD19, CD20, CD21, CD24, CD11a, CD18
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NK Cell characteristics
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are CD16+ and CD56+ lymphocytes, larger than normal lymphocytes, contain aurphilic granules (hence called large granular lymphocytes -- LGL)
CD16 is the FcγIII receptor on surface, but doesnt require this Fc receptor or complement cells ready to kill, dont require activation or any cytokines 2 functions: kill cells adn secrete cytokines |
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NK cell receptors
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2 types:
Recognition receptors- enable NK to see virus infected cell or tumor cell, not as specific as BCR or TCR Inhibitory Receptors- prevent NK from killing normal cells, Killer cell Inhibitory Receptors (KIR) bind to Class I MHC on a normal cell and deliver a signal preventing it from killin normal cell |
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NKR-P1 receptor
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recognizes oligosaccharides, transmitting positive killing signal
IF KIR binds to Class I MHC molecule then an OVERRIDING negative signal delivered thus NK cells have safegaurd against killing normal cells, and allows NK cell to kill infected cells that escape T cell detection by inhibiting MHC Class I molecule expression!! |
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Recognition Receptors
(many, but ones to Know...) |
called KAR (killer activation receptors)
NKG2D -- most common one associated with DAP12 |
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Inhibitory Receptors
(many, but ones to know..) |
called KIR (killer inhibitory/Ig-like Receptors)
KIR2D KIR3D CD94/ NKG2A |
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NK cell activating cytokines
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all activate NK cells;
primarily activate killing: IFN-α, IFN-β, IFN-γ, and TNF-α primarily activates secretion of cytokines: IL-12 |
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NK response
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NK response peaks early post viral infection,
high levels of NK anti-viral activity is IFN-induced; also a result of absolute increase in NK cell numbers from bone marrow response to growth factors (IL-12) |
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NK deficient pt
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more likely to have viral infections
esp, prone to getting herpes viral infections |
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Lymphokinine activated killer (LAK) cell
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derived in vitro by culture of peripheral blook lymphocytes in high does IL-2
these cells show enhanced and NONspecific ability to kill tumor cells; administration of LAK with IL-2 to animal tumor shows regression of metastatic tumors NOTE: administration of IL-2 alone able to induce tumor regression in vivo (probably mediated by indigenous LAK) |
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Tumor Infiltrated lymphocytes (TILs)
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isolated from teh site of the tumor (melanoma) were expanded by culture in IL-2;
resutling TIL were predominantly T cells that expressed LAK-like activity proven more effective than LAK, requiring lower doses of IL-2 than LAK |
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Antibody Dependent Cellular Cytotoxicity (ADCC)
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expression of FcγRIII (CD16) on NK cells (along w/ monocytes, macrophages, neutrophils, eosinophils, but NOT T of B cells) allows ADCC
mechanism simlar to non-antibody dependent killing (ie perforins, granzymes, etc) monocytes, macrophages, and neutrophils mediate ADCC by non-perforin dependent killing by secreting NO, oxygen radicals, TNF-α, and proteases (--> necrosis) Eosinophils ADCC can also be mediated by IgE adn the FcεR |
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Effector Cells of CMI
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Cytotoxic T lymphocyte (CTL)--CD2, CD3, CD8; specific via TCR, recognizes MHC Class I; effector molecules: Perforin, cytokines (TNFβ, INFγ)
Natural Killer cells ADCC-- CD2, CD16, CD56; specific via IgG; effector molecules: Perforin, Cytokines (TNFα, IFNγ) Natural Killer Cell (NK)-- CD2, CD16, CD56; nonspecific; Effector molecules: Perforin, Cytokines (TNFα, IFNγ) Lymphokine-Activated Killer (LAK) cell-- CD2, CD16, CD56; nonspecific; Effector Molecules: Perforin, Cytokines (TNFα, IFNγ) Macrophage-- CD14; nonspecific, Effector Molecules: TNFα, enzymes, NO, oxygen radicals |
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In vitro models of cell cooperation
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showed that elimination of macrophages reduced the antibody response;
need involvement of T and B lymphocytes and macrophages in both primary and secondary responses |
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3 major cell types cooperate in Ig production in response to T-dependent antigen
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1. antigen-presenting cell (APC) ex: macrophage
2. T lymphocyte, esp Helper T cells 3. B lymphcytes, from which Plasma cells arise (plasma cells make bulk of Ig) |
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The Carrier Effect
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proof for cell-cell cooperation in antibody synthesis;
in order to define teh requirements for antibody response to a SINGLE antigenic determinant, use of HAPTEN-CARRIER complex |
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Hpaten and Hapten-Carrier Complex
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Hapten- Single, isolated antigenic determinant, but NOT immunogenic (too small)
but when when covalently bound to carrier protein, can be immunogenic |
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3 rules for the production of a secondary (IgG) response to a hapten
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1. Must be B cells that are exposed to hapten TWICE
2. must be T cells that are exposed to the carrier TWICE 3. must be a covalent bond b/w the hapten and carrier that is recognized by the T cell |
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Antigen processing
Step 1 |
APC are non-specific (except B cell, which are antigen specific);
ingest soluble molecules by endocytosis, digest via lysosomal rxns into peptide fragments |
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Antigen Presentation
Step 1 |
Class II MHC molecules introduced into endosome with peptide fragments from the antigen
the peptides bind nonspecifically and non-covalently to the gooves of MHC II molecules; the complex displayed on cell surface antigen presentation thus limited to cells that express surface class II MHC molecules --> MHC restricted |
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ACP - Helper interaction and activation
Step 2 |
when a helper T cell with TCR specific to the peptide on the MHC class II molecule, then cells undergo a mutual exchange of activation signals (change in gene expression, secretions, cell division, etc)
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cytokines
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secreted hormone-like proteins that are secreted by cells and signal other cells
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activated T cell interaction with ACP
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after binding antigen:
helper T cell expresses IL-2 Receptors and secretes IL-2 (which induces cell division of both T and B cells), CD40 ligand upregulated on T cell, which interacts with CD40 on ACP the B7 antigens (B7.1 adn B7.2; CD80 adn CD86) upregulated on ACP which interact with CD28 on T cell to constimulate it T cell secretes cytokinines: IL-4 (activates B cells), IFNγ (activates macrophages), macrophages secrete IL-1, IL-6, and TNFα (tumor necrosis factor), which all activate T cells and play role as pro-inflammatory cytokines |
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T cell- B cell cooperation
Step 3 |
B cell first activated when antigen binds to surface Ig (antigen specific); B cell internalizes the antigen complex, processes it, and presents them on surface MHC Class II molecule
when ACTivated helper T cell which is specific for the peptide-MHC complex on B cell, then it binds to cell... interaction signals T cell to release many cytokines that are essential for B cell division and differentiation into plasm cells interaction b/w costimulatory molecules CD40 and CD40 lingand are essential for B cell differentiation into memory cells and for class SWITCHING |
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Cytokine-induced B cell differentiation
Step4 |
activated T cell secrete IL-4, IL-5, IL-6, IL-10, cytokines essential for B cell division (AMPLIFICATION) adn differentiation into Ig secreting *plasma cell*
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IL-1
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from: macrophage
target: both (B and T cell) effect; activation (inflammation) |
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IL-2
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from: Helper T cell (TH1)
target: T cell, B cell, NK cell effect: cell division |
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IL-4
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from: Helper T cell (TH2)
target: both (B and T cell) effect: activation and differentiation |
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IL-5
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from: Helper T cell (TH2)
target: B cell effect: differentiation |
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IL-6
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from: Helper T cell (TH2), macrophage
target: both (B and T cell) effect: activation and differentiation |
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IL-8
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from: macrophage
target: neutrophil effect: chemotaxis |
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IL-10
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from: Helper T cell (TH2)
target: Helper T cell (TH1) effect: INHIBIT cellular immunity |
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IL-12
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from: macrophage
target: Helper T cell (TH1), NK cell effect: activation |
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IL-13
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from: Helper T cell (TH2)
target: B cell effect: activation (IgE synthesis) |
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TGF-β
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from: Helper T cell (TH2)
taget: B cell effect: activation (IgA synthesis) |
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TNF-α
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from: macrophage, NK cell
target: endothelial cell effect: Inflammation, toxicity |
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TNF-β
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from: Cytotoxic T cell
target: endothelial cell effect: inflammation, toxicity |
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IFN γ
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from: Helper T cell (TH1)
target: MACROPHAGE effect: ACTIVATION |
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T-dependent antibody response
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thymus dependent response to complex protein antigen produces memory response with high affintiy IgG antibodies;
antigens that activate B cells in abscence of significant T cell help are T-independent antigens they induce primarily IgM with kinetics of a primary response (even on subsequent exposures) T-independent antigens are usually large polymers with repeating epitopes (like a polysacc)- the multiple epitopes can crosslink B cell surface Ig and stimulate proliferation and IgM production |
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Tolerance
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specific absence of an immune response to antigen to which there has been prior exposure to
ability to distinguish self from non-self |
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General properties of Immunogenic tolerance
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1. tolerence is iummunologically specific
2. tolerance is learned or acquired 3. immature/developing lymphocytes from susceptible to tolerance induction than mature/developed or functionally competent cells 4. tolerance to foreign antigens can be induced in mature lymphocytes when cells are exposed to antigens under conditions that are inadequate for activation |
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Factors that determine tolerogenicity of an antigen in adults
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1. routine administration of antigen- intradermal or intramuscular optimal (IV or oral not)
2. structure or form of antigen- aggregate or particulate antigen is immunogenic but disaggregated, monomeric antigen is telerogenic 3. dosage of antigen- extremes (very high or very low) doses induce tolerance |
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Mechanism of T cell tolerance
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1 Deletion of self reactive clones of THC and CTL in thymus
2. clonal anergy- lymphocytes stimulated int eh absence of costimulator molecules on antigen presenting cells are unresponsive to subsequent stimulations with teh same antigen 3.clonal supression- T or B cells with autoreactivity are actively supressed from functioning |
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Clonal anergy mechansim
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lies in nature of innate immune system;
up regulation of costimulatory molecules (B7) on antigen presenting cells necessary to get response out of antigen specific T cell; but B7 not expressed until induced by recognition of pathogen associated pattern molecules by the APC... since self antigens don't have this extra pathogen-associated pattern molecule, ingestion by APC fails to upregulate B7, resutling in T cell tolerance rather than a autoimmune response |
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Regulatory T Cell (Treg)
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differentiate from CD4+ T cell; constantly express α chain of teh IL-2 receptor (CD25), the transcription factor FoxP3, and are CD4+
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T cell suppression
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Treg supress by cytokine release that inhibit lymphocyte resonses;
consumption of cytokines needed for T cell activation; antagonistic effect of different cytokines produced by different populations of TH cells |
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tolerogen
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antigen that is to be tolerized (could be self antigen or foreign)
if present in thymus then reative T cells negatively selected; if not, then alternate mechanism |
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autoimmunity
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loss of tolerance; T cells attack self antigen
strong genetic component; associated w/ particular antigens of the HLA complex |
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immune system regulation
ON/OFF |
regulation of the antibody response can occur at the antigen, antibody, or T lymphocyte level
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antigen level regulation of response
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in vivo level of antigen of proven immunogenicity determined by rates of metabolic and immune elimination;
as antibody conc inc, free antigen should dec. until insufficient for lymphocyte activation |
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antibody level regulation of response
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1. antigen blockade- production of specific antibody and its antigen blcok the recognation fo teh epitope by B cels
2. feedback inhibition by antigen-antibody complex-- complex interacts with B cell via sIg(specific antigen receptor) and Fc receptor.. B cell not activated 3. generation of anti-idiotype antibody specificities-- increasingly specific idiotypes as response progresses, amy mimic antigen resulting in increased lymphocyte activation, but may be blocked by anti-idiotype antibodies |
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Cytokine medicated regulation of response
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may have synergistic effect, antagonistic effect, can influence type of immune response;
cross regulation |
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Cross regulation by T cell subsets
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cytokine dictates type of immune response and lymphocyte activity:
TH1 produces IFNγ, activating macrophages and inhibiting TH2 proliferation-->DTH TH2 produces IL-4 and IL-5 that activate B cells AND IL-10 that inhibits TH1 production (thus inhibiting Cellular immunity) Treg produces inhibitory cytokines (IL-10) that down regulates immune responses--crucial for maintianing self-tolerance |
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Activation Induced cell death
(AICD) |
prevents over activation of appropriate immune responses to foreign antigen
when T cells activated, a significant portion die just from the activation; only a portion of them live on as memory cells during activation of T cell by APC, CTLA-4 expressed on T cell CTLA-4 --- an alternate receptor for costimulatory B7 molecule; appears after antigen activation of the T cell, out-competes CD28 to bind to B7, producing a negative signal-->turning off the activated T cell |
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Complement
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a group of interacting plasma proteins, act collectively
seem to help or "complement" antibody activity to destroy bacteria |
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Proteins of complement system
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eleven different proteins
named C1, C2,...C11 fragments from proteolytic designated by lower case letter (e.g. C2a) |
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subunits of C1
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three:
C1q, C1r, C1s |
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C3 fragments
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C3a and C3b
fragments that result from proteolytic cleavage |
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alternate pathway compnents
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named by a single letter code (upper case)
Factor B (B) Factor D (D) Proprdin (P) |
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control proteins of complement pathway
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given descriptive names
C1 inhibitor (C1-INH) C3b inavtivator (I) |
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Initiation of classical complement pathway
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when IgM, IgG1, IgG2, or IgG3 bind to antigen, a previously unavailable Fc site exposed; C1q bind to site
C1 considered to the cognition unit of the complement system |
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C1 complex
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a flower like structure;
made of C1q (stalk) 2 C1r and 2 C1s petals all units held together by Ca++; removal of ca++ causes complex to dissociate and prevents activation C1q binds to antibody, inducing conformational change in C1r; [Reciprical activatin of 2 C1r units on each other] C1r enzymatically acts on itself and C1s--> active enz from C1 |
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Classical Complement pathway
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1. C1qr2s2 binds to 2 antibodies; enz of C1 activated
2. C1s enz cleaves C4 into C4a and C4b; C4b binds to C2a irreversibly (C4b2a= C3 convertase) 3. C3 convertase cleaves C3 into C3a and C3b; C3b binds to C4b2a complex (C4b2a3b= C5 convertase) 4. C5 convertase cleaves C5 into C5a and C5b 5. C5b binds C6 and C7 and C8 to from C5b678 complex 6. C5b678 complex binds to multiple C9 forming MAC on target cell membrane as a channel (--> lysis) |
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Opsinization by complement
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when particulate encapsulated antigens become coated with C3b, this fragment can interact with specific receptors on phagocytic cells triggering adherence and then particle ingestion
the most important biological activity of complement, mediated by breakdown fragments of C3b (iC3b, C3dg) which bind to different receptors on phagocytes clearance of immune complexes is also dependent on C3 fragment deposition |
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Kinin- like activity
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small fragments released from C2 during activation (C2b) is further degraded by plasmin to release a small peptide with kinin-like activity
kinins are vasoactive peptides that cause increased vascular permeability, edma, and pain |
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Anaphylatoxins
|
small fragments C3a, C4a, C5a interact with receptors in basophils and mast cells causing granule release;
the granules contain a variety of vasoactive and inflammatory mediators including histamine and heparin; the cells also synthesize prostaglandins and leukotrienes which also mediate inflammation; the net effect is smooth muscle contraction, bronchial constriction, and increased vascular permeability |
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Chemotaxis
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C5a has an additional activity which directs cell movement:
C5a and C5a des arg cause neutrophils, eosinophils, monocytes, and mcarophages to migrate towards higher concentrations of the molecules, thus accumulating at sites of infection, inflammation, or immune reactions; At high concentrations, C5a also activates the phagocytic cells, making them more metabolically active |
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Lysis
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C5b6789 complex (C5b-9) assembles on a membrane, inserts a channel, and produces a disruption of the target cell’s ability to regulate solute and ionic gradients;
The target cell may swell and burst, or just lose internal proteins causing death--> LYSIS Gram positive organisms, fungi, and protozoal parasites are resistant to this lytic effect --Only gram negative bacteria can be killed by C5b-9 (ex: Neisseria) |
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Opsonin fragments
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C3b, iC3b (C4b, C5b)
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Kinin fragments
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C2 fragments
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Leukocyte mobilization fragment
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C3e
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Anaphylatoxin (inflammation) toxin
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C5a, C3a, (C4a) -- (all "a" fragments released)
local effects necessary but systematic inc. causes edema/shock |
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Chemotaxis fragments
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C5a, (C5a des arg)
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Lysis fragment
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C5b-9 (C5b-8)
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Alternative pathway
|
aka Properdin pathway
this pathway can be activated by antigens without antibody involvement most important in early stages of infection |
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Reaction pathway of alternate pathway
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1. hydrolysis of C3; a SPONTANEOUS rxn
2. formation of fluid phase C3 cleaving enz (C3 convertase) C3(H20) + B --> --> C3(h20)Bb + Ba 3. cleavage of new, native C3 molecule into C3b* and C3a by C3 convertase 4. metastable C3b* binds covalently to surface -- C3b deposited on antigen surface, and binds to B, D, Mg++ to form C3bBb <-- second complex of alternate pathway (C3b-dependent C3 convertase) this enz unstable, but binding of Properdin (P) stablizes it -- enz (C3bBbP) cleaves more C3 into C3a and C3b (amplification) -->POSITIVE FEEDBACK LOOP -- 3rd multiunit enz of alternate pathway is C5 convertase; formed from a C3b addition to the C3bBbp enz--> C(3b)2BbP which converts C5 into C5a and C5b -- C5b initiates the membrane attack cascade: C5b +C6, C7, C8, C9 --> C5b-9 --> LYSIS |
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Control of alternate pathway
|
need to control C3 activity (esp b/c positive feedback amplification)
the complexes naturally decay with loss ob Bb, even from Properdin stabilized enz complexes Factor H accelerates this decay process also Factor H and Factor I (C3b-inactivator) cleave teh C3b into inactive fragments (C3b --> iC3b, C3c, and C3dg |
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Activators of the alternate pathway
|
Activated by many complex polysaccharides of years or bacterial cell walls, etc
IgG1, IgG2, IgG3, IgA, and IgE activate it as well If the surface is an activator, structures on the surface protect C3b from the control proteins |
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Mechanism of activation
|
determining factor is nature of surface on which C3b is bound;
if surface is non-activator (normal cell, some viruses, etc) then Factors H and I rapidly inactivate the C3b if surface is activator then, surface protects C3b from inatctivaion, allowing the cascade to continue |
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consequences of alternate pathway
|
nearly all of effects of teh classical pathway can be generated;
opsonization, chemotaxis, anaphylatoxin, lysis ex: rabbit RBC activate alternate pathway in humans and lead to their lysis (test for alternate pathway) |
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Control mechanism of complement pathway
|
3 types:
a. Decay of the C3 and C5 cleaving enzs by loss of C2a or Bb dissociation (short lived enz) b. Labile binding sites- covalent binding of C3b or C4b must happen fast or else thioester bond will react with water, inactiviating it similarly C5b must bind to C6, adn teh C5b67 complex to a hydrophobic surface in .1 sec or else inactivated! c. control proteins on cells surfaces: * CD55 – also known as decay accelerating factor (DAF) dissociates C2a and Bb from bound C3 convertases * CD35 – aka complement receptor Type 1 (CR1) dissociates Bb from bound enzymes and acts as a cofactor for I cleavage of C3b * CD46 – aka membrane control protein (MCP) is a cofactor for I cleavage of C3b * CD 50 – aka homologous restriction factor, binds to C8 and C9, preventing the assembly of C5b-9 on homologous cell surfaces, thus protecting the host from lysis |
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Control protein of alternate pathway on cell surface
|
* CD55 – also known as decay accelerating factor (DAF) dissociates C2a and Bb from bound C3 convertases
* CD35 – aka complement receptor Type 1 (CR1) dissociates Bb from bound enzymes and acts as a cofactor for I cleavage of C3b * CD46 – aka membrane control protein (MCP) is a cofactor for I cleavage of C3b * CD 50 – aka homologous restriction factor, binds to C8 and C9, preventing the assembly of C5b-9 on homologous cell surfaces, thus protecting the host from lysis |
|
Control proteins of alternate pathway in PLASMA
|
* C1-inhibitor: binds C1r and C1s, irreversibly inactivating these enzymes and dissociating C1r and C1s from C1q
* C-4 binding protein (C4bp): competes with C2 for binding to C4b; also acts as a cofactor for the breakdown of C4b by Factor I * b1H (Factor H): acts as a cofactor for Factor I in the breakdown of C3b to iC3b; H also competes with Factor B for binding to C3b *C3b/C4b inactivator (factor I)- enz that breaks down C3b and C4b *Properdin- stabilizes C3 and C5 cleaving enz; positive regulator * S protein (vitronectin), C8, and lipoproteins: all bind to C5b67, preenting its attachments to membranes * Carboxypeptidase N: inactivates C3a, C4a, and C5a anaphylaxotoxins by cleaving off the carboxyterminal arginine. |
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Lectin
|
anthing binds to carbohydrate/polysaccharide
|
|
Lectin Pathway
|
third complement pathway;
initiated by binding of a recognition molecule-- C1q-like molecule Mannose-Binding Lectin (MBL), like C1q, circulates with 2 serine proteases- MBL-associated Sereine Protease 1 and 2 (MASP 1 and MASP 2), which are similar to C1r adn C1s MASP cleave C4 and C2, which activate rest of classical pathway (activates C3 convertase) lectin pathway NOT activated by specific anibody, but rather by MBL binding to mannose and other complex carb polymers |
|
Complement Receptors
|
Receptor for C1q and MBL are opsonins;
C5a receptor on phagocytes mediates chemotaxis C5a, C3a, and C4a on basophils mediate granule release/inflammation C3 receptors: *CR1 (CD35)- binds C3b, C4 b on RBC, phagocytes and B cells *CR2 (CD21)- binds iC3b, C3d, C3dg on B cells and follicular dendritic cells *CR3 (CD11b/CD18)- binds iC3b on phagocytes *CR4 (CD11c/CD18)- binds iC3b on phagocytes |
|
Primary (inborn) deficiencies of C components
Genetics |
1. Homozygous C component deficiency have been identified or each component of the classical pathway as well as for properdin and Factor D
2. Autososmal codominant inheritance of all the C system deficiency genes have been identified except properdin, which is X-linked 3. Genes for C2 and C4 deficiency have been linked to certain HLA alleles, along with geners for Factor B, (mapped to a region on chromosome 6) Suggests possible role for C in immunoregulation |
|
Primary (inborn) deficiencies of C components
Complications |
1. Deficiency of C1q, C2 or C3 a pt show increased susceptibility to infection by encapsulated bacteria resulting from decreased serium opsonic activity
2. Deficiency of C5,C6,C7,C8,properdin – propensity to Neisserial sepsis 3. Deficiency of a classical pathway component – incidence of C-mediated dermatitis, lupus, arthritis, nephritis Reflects role for C in clearance of immune complexes and infectious agents |
|
Primary (inborn) deficiencies of C components
Treatment |
Managing infections;
infusions of fresh plasma from normocomplementemic donors (temporary) |
|
Deficiencies of a C regulatory Protein
C1-esterase inhibitor (C1-INH) |
Genetic form – decreased levels of C4, C2, and CH50;
Acquired form – C4, C2, CH50+ C1q; Uncontrolled, fluid-phase activation of C4 and C2, lowering both; presents with Angioedema --Treatment:Androgens (anabolic steroid therapy) increase C1-INH and C4 levels; Transfusion replacement therapy |
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Deficiencies of a C regulatory Protein
C3 regulatory protein defects |
Both inborn and acquired;
“C3 nephritic factor”, an acquired autoantibody to the alternative pathway C3 convertase, impedes the function of Factors H and I --hypercatabolism of C3 is the result, and attending complications are those of C3 deficiency; pyrogenic bacterial sepsis and glomerulo-nephropathy; --Treatment: antibiotics and anti-inflammatory (prednisone) |
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Deficiencies of a C regulatory Protein
Complement receptor deficiencies |
C receptors-- Lacking CR3 or CR4 have immunodeficiency syndrome including ulcerating infections, susceptibility to bacterial infections and abnormal wound healing
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Deficiency of C1q, C1r, C1s, C4, or C2
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SLE, SLE-like, chronic renal disease, anaphyactoid prupara, dermatomyositis, inflammatory bowel disease, repeated infections
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Deficiency of MBL
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multiple infections
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deficiency of C3
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repeated infections; immune complex disease (can't opsonize)
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C5, C6, C7, or C8
P or D Deficiency |
repeated gonococcal infectiosn,
repeated meingococcal memingitis, (rare: renal disease, SLE) can't lyse cells |
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Deficiency C1-INH
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hereditary angioedema; organs swell up
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Deficiency of C3b-INA, C3 receptors (CR3 & CR4)
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repeated infections;; uses up all C3, so C3 deficient
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deficiency of β1H
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repeated infections, hemolytic uremic syndrome
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deficiency of CD59 and maybe CD55 (DAF)
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paroxysmal nocturnal hemoglobinuria
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MONOCLONAL ANTIBODIES
Kohler and Milsten |
* fusion of a plasma cell myeloma with spleen B cells from an immunized mouse resulted in a somatic cell hybridoma that synthesized and secreted immunoglobulin and could be propagated in tissue culture
* genetic information from the splenic B lymphocyte coded for the immunoglobulin and the myeloma cell provided “immortality” in tissue culture * selection and propogation of a single cell producing antibody results in a cell line producing a homogenous, monoclonal population of immunoglobulin’s |
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MONOCLONAL ANTIBODIES
Cell fusion |
* two somatic cells can be fused (hybridized) using viruses, sendai virus, or chemicals such as PEG:
o because it is relatively non-toxic and yields a high incidence of fustion, PEG has become a standard funsogen for a wide variety of different cells o PEG first promotes cell-cell adhesion + Important, because usually cells normally not get close to each other due to mutual electrostatic repulsion and by the exclusion volume of membrane glycoprotein’s and the glycocalyxmacromolecules + In the presence of PEG the distance between cells is reducesd to less than 5nm + Continued dehydration by PEH induces the lateral aggregation of glycoprotein’s within the lipid bilayer of the cell membrane, exposing mall areas of denuded lipid bilayer in each of the contacting cells + When small plaques of denuded membrane exist in two adjacent cells, fusion can occur via lipid-lipid interactions between adjacent cell and small sytoplasmic connections can be found between cells + Removal of the PEG and reintroduction of water causes the influc of Ca and other ions and water # The swelling of the cell expands the cytoplasmic connections, forming a spherical fused cell * Cyptoplasmic fusion is followed by nuclear fusion |
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MONOCLONAL ANTIBODIES
Hybridoma Selection |
* following the usion of splenocytes and myeloma cells, several cell types populate the cell mixture including:
o unfused myeloma cells o unfused spleen cells o myeloma-myaloma hybrids o splenocyte-splenocyte hybrids o hybrids resulting from the fusion of more than two cells * it is therefore necessary to either select for the myeloma-splenocyte hybrid (positive selection) or select against the unfused myeloma or myeloma-myeloma hybrid (negative selection) o selection against spleen cells or splenocyte-splenocyte hybrids is not necessary because these cells have a finite life span and die rapidly in tissue culture * most non-Ig secreting myeloma cell lines used for generating hybridomas are variants that contain a mutation in the enzyme HGPRT o the HGPRT-parent of hybrid can be selected against because it will not grow in medium containing the folic acid analog, aminopterin which blocks de novo synthesis of purine and pyrimidine nucleotide o a hybrid cell without HGPRT will not grow in medium containing aminopterin supplemented with exogenous HAT while a cell with HGPRT can utilize the exogenous nucleotides nucleotides for DNA synthesis and multiply * the spleen cell-myeloma hybridoma which grows out from HAT selection will include hybrids producing Ig not specific for the immunizing antigen * screening for and selection of antigen-specific hybridomas can be done in a variety of ways and the method used is based on the ultimate application of the monoclonal o most commonly used are solid phase binding assays such as enzyme-linked immunosorbent assays (ELISA) o once selected, the specific hybridoma can be cloned in vitro and expanded in vivo |
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MONOCLONAL ANTIBODIES
Hybridoma Production |
* hybrid cell contains chromosomes from both parental cells
* as the hybrid cell divides, some genes are lost * fused cells from different species (heterokaryon) will rapidly lose chromosomes from one species * fused cells from the same species will lose chromosomes randomly until the hybrid is around 3N * Loss of spleen cell chromosomes from a B cell hybridoma during culture can be the cause of unstable antibody production o Immunoglobulin H and L chains are encoded on different chromosomes, any one of which can be lost + H chain synthesis is frequently lost before the L chain * The first report of a hybrid cell that secreted immunoglobulin described the fusion of cells from two different myelomas and also a myeloma and a lymphoid cell * Important principles: o Immunoglobulin expression is codominant + i.e. both immunoglobulins made by the parent cells are also made by the hybrid cells o If both parental cells produced immunoglobulins, then the hybrids can assemble heavy (H) and light (L) chains into all possibly combinations of H2L2 (hybrid antibodies) o Myeloma cells fused to cells that are not in the B-cell differentiation lineage switch-off immunoglobulin synthesis o When a spleen cell capable of producing an antibody (e.g. anti-SRBC) is fused to a myeloma cell no longer producting antibody, the hybrid cell continues to produce antibodies, in this case anti-SRBC antibodies and the immunoglobulin genes from the non-producing myeloma variant are not activated * Non-Ig producing myeloma variant and a B cell with a potentially desired specificity from an immunized individual are the preferred fusion partners for the production of a B cell hybridoma |
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MONOCLONAL ANTIBODIES
Properties and Applications of Monoclonal Antibodies |
* monoclonal antibodies are a homogenous population of immunoglobulin’s as to idiotype, affinity, and isotype
* specificity of mAb however may be cross-reactive with a mimicking epitope on molecule which is not identical or even related to the immunizing antigen * the ability of a monoclonal antibody to mediate precipitation or agglutination reactions will depend on the frequency of the epitope with which it reacts on the antigen * monoclonal antibodies reactive with different sites on an antigen may be mixed to produce an artificial but well-defined polyclonal antibody reagant * a monoclonal antibody may be biologically active or inert, depending on whether it is an appropriate isotype for activating complement or interacting with FcR on phagocytic or killer cells * these monoclonal antibodies are used with radiolabels for the in vivo identification of tumors by scintography and for regulation of the immune response and mAbs to neurotransmitter and receptors may be therapeutically valuable in neruological diseases |
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MONOCLONAL ANTIBODIES
Further Developments |
* therpeutic use of murmine mAb is limited by the production of human anti-mouse antibodies (HAMA) and in some cases by the relatively inefficient effector functions mediated by murine Fc
* humanization and potentially therapeutic mAb are being conducted currently * recombinant DNA and gene transfection techniques allow the redesign of Ig genes and molecules and the construction of chimeras * the simplest humanized antibody joins an intact mouse V region to an intact human C region * The V region is chosen for the target specificity, e.g. a tumor cell * The constant region isotype is chosn on the basis of the intended use * For imaging of delivering of a toxin, the preferred isotype might be biologically ‘inert’ (IgG2/4) * For mediating tumor cytotoxicity and cell damage, IgG1/3 would be necessary * Another approach to increasing the therapeutic efficacy of mAbs in the treatmenr of cancer and infectious diseases used bispecific mAbs for targeted cellular cytotoxicity * Bispecific mAbs can be made by chemical cross-linking, by fusing hybridoma cells with 2 differenct V regions and by molecular genetics approach * Bispecific mAbs bind to target cells by one V region and cytotoxic cells by the other V region, triggering cytokine release and cytotoxicity * Another development in genetically engineered bispecfic molecules is a fusion protein, an example of which is a molecule containing CD4 linked to the Fc region of human IgG * The CD4-Fc fustion protein is now being tested in clinical HIV trials |
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Phagocytosis
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process by which particular matter is engulfed and degraded in a cell;;
in endocytosis- soluble macromolecules taken into cell |
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Mononuclear Phagocyte System (MPS)
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aka Reticuloendothelial systesm (RES)
Makeup * Monocyte in Blood * Macrophage in tissue o Kupffer cells in liver (most numerous of all tissues) o Aveolar macrophage in lung * Mesangial macrophages in kidney * Microglial cells in CNS * Tissue macrophages in peritoneal * Lymphoid tissue Macrophages |
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Functions of the mononuclear phagyocyte system
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Antigen clearance
o When particulate antigen is injected intravenously it is cleared from the circulation by the mononuclear phagocyte system Clearance of damaged cell o Cells of RES, particularly splenic macrophages and Kupffer cells, are effective at removing damaged or old, non-functional cells by phagocytosis o At sites of wound healing, tissue macrophages remove fibrin deposits, trapped red cells, and dead or damaged tissue and debris o These products are then degraded by lysosomal enzymes and reuitilized by the body Giant cell formation o When the macrophage phagocytizes particles, it undergoes substantial morphological and metabolic changes and can transform into an epitheliod which lacks granules + This occurs when there is a failure to remove particles o In lesions where a large number of macrophages are actively involved in phagocytosis, when there is chronic inflammation where particles are not effectively eliminated,or when a very large particle is introduced, the epithelioid cells may fuse to form multinuclear giant cells called granulona which acts to wall off the particle from the rest of the body tissues |
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Manipulation of the MPS
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MPS blockage
o Injection of a high does of inert particles + Colloidal carbon, gold, thorium oxide particles, lipid emulsions MPS stimulation o Enhanced by serotonin, bacteria extracts, and endotoxin o May be useful in providing an additional measure of resistance + Eg: cancer immunotherapy using BCG |
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Granulocytes
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* first line of active cellular defense against invading extracellular pathogens are the polymorphonuclear leukocytes (PMNS)
* unlike the cells of the RES which have multiple functions besides phagocytosis, the PMNs are aggressively phagocytic, and have few other functions * neutrophils, eosinophils, and basophils |
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Granulocyte functions
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* Basophils
o Have granules which contain heparin and histamine that are released upon the interaction with complement derived anaphylatoxins or antigen complexed to cytophlic IgE o They are less avidly phagocytic than neutrophils o Make up 1% of circulating leukocytes o Important in allergic reactions * Eosinophils o Slightly less avidly phagocytic than are neutrophils o 305% of the circulating leukocytes in normal adults, bur their numbers increase dramatically in atopic (allergic) conditions or during parasitic infections o major role is host defense against parasites, but also release mediators which play an important role in local inflammatory responses * Neutrophils o 65% of the leukocytes o aggressively phagocytic and are the body’s major cellular defense against extracellular bacterial pathogens |
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Nautrophil phagocytosis
* production |
made in bore mrrow and are produced quite rapidly, since their half life in circulation is only 6-7 hours
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Nautrophil phagocytosis
* mobilization |
during an episode of infection or inflammation, neutrophil counts may rise dramatically
mobilization is due to the release of cells from storage pools in the body, and not necessarily reflective of an increased synthetic rate in the bone marrow; two major sources: -marginal pool; + large number of PMNs in the blood are not circulating freely, but are attached to blood vessel and capillary walls; unavailable when blood is drawn for a cell count; released very rapidly (less than 5 minutes) upon intro of stimuli such as epinephrine -granulocyte and monocyte reserve + large store of mature monocytes, neutrophils and band cells stored in the bone marrow; cells are released into the circulation at a rate sufficient to keep the PMN count roughly constant, since PMNs are constantly migrating out of the circulatory system and into the tissues; can increase, causing leukocytosis bacterial endotoxin is every efficient at stimulationg such a release, and can be used as a measure of granulocyte reserve rxn takes 6-12 hours to reach its peak; Cytokines (IL-1 and TNFa), glucocorticoids, and C3e mediate mobilization, bacterial endotoxin |
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Nautrophil phagocytosis
* chemotaxis |
chemotactic factors are the soluble molecules which mediate migration
* When chemotactic factors are generated at a particular site, they diffuse over a distance, establishing a concetration gradient; PMNs interact with the chemotactic factors through receptors on their cell surfaces and migrate up the concentration gradient, towards the site of chemotactic factor origin or generation * Chemotactic factors: o C5a and C5a des arg are the most important (plasma chemotactic factor) o F-met peptides (prokaryotes like bacteria) o IL-8 (stimulated Macrophage) – a chemokine o Leukotriene B4 (LTB4) (stimulated PMNs) |
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Nautrophil phagocytosis
* opsonization |
Neutrophil lacks the inherent ability to distinguish “foreign” from “self” surfaces, some type of marker is required... ieopsonins which bind to a particle and to a receptor on a neutrophil and can initiate phagocytic events
Types: o Alternative and Lectin complement pathways + C3b and iC3b + Many bacterial surface products can activate the alternative of lectin pathways in the absence of any specific antibody + Activations results in the deposition of C3b and iC3b on the bacterial surface, acting as opsonins + PMNs and macrophages have receptors for C3b and iC3b on their surfaces + This pathway plays a critical role in defense against bacteria in the early stages of a first infection – before antibody has been synthesized to the bacterial antigens o Antibody and the classical complement pathway + Complement activating antibodies (IgM, IgG1,2,3) are extremely efficient at depositing C3b on the bacterial surface (via C1, C4, and C2) thus opsonizing the particle for ingestion + Antibody mediated C3b deposition is more efficient than the alternative or lectin pathways, so that this reaction sequence is the major opsonic pathway when some specific antibacterial antibody is present o IgG alone + Since PMN’s have Fc receptors for IgG, high leels of specific IgG antibody can be opsonic even in the absence of complement It is clear from pt studies that BOTH IgG antibody and C3b or iC3b are needed for adequate host defense against extracellular bacterial pathogens, since EITHER C3 deficiency or IgG deficiency predisposes to severe, recurrent infection with encapsulated bacteria |
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Nautrophil phagocytosis
* engulfment |
Attachment of opsonized particles to cell surface opsonin receptors initiates the engulfment process,
the particle is ingested, the external membranes surrounding it is pinched off, forming a vacuole around the particle-- called a phagosome Uptake process requires the assembly of actin and myosin into microfilaments which requires metabolic energy (obtained mainly through anaerobic glycolysis) |
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Nautrophil phagocytosis
* Degranulation |
Lysosomal granules fuse with phagosome, releasing their contents into the vacuole
o now called a phagolysosome two types of lysosomal granules called primary (azurophilic) granules and secondary (specific) granules (because of the time of their appearance during development of the cell( o Specific granules compose 75% of the granules and release their enzymes first 0-3 minutes after ingestion; pH optimum near 7 o Primary granules release their contents 7-10 minutes after ingestion; pH 4.5 Extracellular release of lysosomal enzymes is a major cause of tissue damage during inflammation |
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Nautrophil phagocytosis
* Metabolic Stimulation |
* Increased phoshatidyl inositol synthesis
* Increased Ca uptake * Increased glycogen breakdown * Increased anaerobic glucose metabolism which supplies energy for phagocytosis and chemotaxis; the end product is lactate, since PMNs are relatively deficient in PDH * Lactate buildup results in decresed intraphagolysosomal pH to 4.5; lysosomal enzymes activation and release then occur * Amount of glucose metabolized via the hexose monophosphate shunt (HMP) increases from 2% of the glucose used (resting) to 50% (phagocytizing); this supplies cytoplasmic NADPH which is reoxidized through non-mitochondrial oxygen uptake through the enzyme NAPDH Oxidase, which produces the superoxide anion (.O2-) |
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Nautrophil phagocytosis
* Killing |
* H2O2 reacts with the enzyme meloperoxidase (MPO), which is present in high levels in PMN primary granules, and has a pH optimum of 4.5
* A halide ion, Cl- or I-, is required for enzyme activity, and killing of ingested viable organisms occurs through oxidation of bacterial surface and internal constituents * Chemiluminescent (light) emission accompanies oxidative killing * Non-oxidative killers à lysosomal enzymes, defensins; account for 2% of the killing * Oxidative killers à superoxide, hydrogen peroxide, hydroxyl radical, singlet oxygen, MPO, chlorine, choramines (R-NHCL), iodonium, hypochlorous acid (HOCL); Very toxic, and kill any organism ingested by the neutrophil Macrophages use oxidative killing to a lesser degree, thus they can survive the process |
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Defects of Neutrophil Function:
* Defective neutrophil production |
* Results in the depletion of neutrophil counts (neutrophenia)
* May be drug induced, production of anti-neturophil antibodies, secondary to leukemia * Often a finding in other neutrophil dysfunction diseases in which the primary defect is considered to be in one of the other stages of phagocytic cell function * Patients with neutropenia are at risk for bacterial infections |
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Defects of Neutrophil Function:
* Defective mobilization and chemotaxis |
* Intrinsic movement defects are known to occur in lazy leukocyte syndrom (leukocyte adhesion deficiency) and chediak-higasi syndrome.
* Also transient movement defects reported in newborn infants and in patients recovering from some viral infections, such as influenza |
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Defects of Neutrophil Function:
* Defective opsonization |
* Recognition function in phagocytosis is performed by humoral factors, and defects in these have been reported to result in abnormal opsonization
* Agammaglobulinemia, C3 dificiency, and opsonin receptor (CR3/CR4) deficiency (aka leukocyte adhesion deficiency – LAD) due to the absence of CD18 molecule, which is the common b chain of the b2 * These defects are all due to a genetic deficiency of an opsonin or its receptor * Secondary opsonic defects have been reported in patients with systemic lupus erythematosus (SLE) due to consumption of opsonins by immune complexes * Patients with these defects are at risk for recurrent and frequently life-threatinng bacterial infections |
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Defects of Neutrophil Function:
* Defective degranulation |
* Release of lysosomal enzymes into the phagosome has been reported only in Chediak-Higashi syndrome
* PMNs of these patients hae giant lysosomal granules which can be seen in peripheral blood smears * Genetically transmitted, autosomal recessive disorder * Lysosomal enzyme content is nearly normal, but maldistributed, and the rate of degranulation is markedly depressed * Defects in the granules of NK cells result in markedly reduced NK function, and defects in the granules of melanocytes results in partial albinism |
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Defects of Neutrophil Function:
* Defective metabolic stimulation and killing |
* Glucose-6-phosphate dehydrogenase (G-6-PDH) is an essential enzyme in the HMP; its absence in the PMN results in a failure to reduce NADP to NADPH; thus hydrogen peroxide formation is severely impaired
* Chronic Granulomatous Disease (CGD), the enzyme directly responsible for hydrogen peroxide production is absent (NADPH Oxidase) Note that if H2O2 comes from another source (e.g., the bacteria itself in the case of catalase negative organisms) killing is not defective, even tho no metabolic stimulation occurs; Catase negative bacteria secretes H2O2 as a waste product and supplies the missing product to the neutrophil, allowing the MPO to produce toxic oxidants necessary for killing In CGD patients, severe infections with catalse positive bacteria and fungi: + Staphylococcus aureus + Klebsiella pneumoniae + Serratia marcescens Nitroblue tetrazolium (NBT) dye reduction test is a good indicator of oxidative metabolism in neutrophils: Soluble, almost colorless dye is reduced to a dark blue insoluble precipitate in the presence of superoxide anion; negative in CGD MPO deficiency – infections are not nearly as severe as in CDG; due to the action of the oxygen intermediates generated spontaneously from superoxide, which is produced in elevated amounts, since NADPH oxidase is intact |
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Chronic Granulomatous Disease (CGD)
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deficiency of NADPH oxidase
(any 1 of 4 components; failure to generate superoxide anion, and otehr O2 radicals recurrent infections w/ Catalase positive bacteria &fungi |
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Leukocyte Glucose-6-P DH deficiency
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deficiency of essential enz in HMS
same symptoms as CGD |
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Myeloperoxidase deficiency
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ganule enz deficiency
mild or no symptoms |
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Leukocyte adhesion deficiency
(LAD) |
deficiency of CD18 = β chain of β2 integrin - LFA-1, CR3, CR4
recurrent infection w/ extraceullular bact pathogens due to defectivive opsonization, adhesion, mobilization, and chemotaxis |
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Chediak-Higashi Syndrom
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granule structural defect;
recurrent infection w/ bacteria; chemotactic and degranulation defects, lack NK function; partial albinism |
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Cell adhesion molecules
4types |
1. cell adhesion molecules (CAM) of the Ig superfamily (IgCAMs)
2. integrins 3. selectins 4 cadherins |