Adaptive Immunity Flashcards
RAG gene
Allows recomb of gene segments that encode antigen receptors
Acquired immunity characterized by
Clonal distribution and selection and acquisiton of memory
Vaccine strategy
First injection is primer and second is booster
HUmoral immunity
B cells secrete antibody
Cell mediated immunity
TCR either by direct contact or secretion of cytokines
Innate vs. adaptive
Adaptive longer, variable, selective and improves
If pathogen changes,
BCR and TCR will probably be able to adapt to the response
Initial response takes about
7 days
Class 2 function
Initiate response
Class 1 function
Distinguish from normal cell
MHC 1 genetic
HLA-A, HLA-B, HLA-C (chromosome 6) - codes for heavy chain
Beta 2 microglobulin gene on 15
Co-dominant expression (express 6 different class 1 molecules)
Lots of polymorphisms in population
Each allele binds a different spectrum of peptides
MHC class 2 genetic
HLA-DR, HLA-DQ, DHL-DP - codes for 2 distinct protein chains
Co-dominant
Up to 16 different
Polymorphic
Each binds different spectrum of peptides
Which class is more important in transplants
MHC 2
Viral infections may reduce expression of which genes of MHC
HLA-A and HLA-B
Professional APCs express
Both MHC 1 and 2
MHC class 1 expression
From intracellular pathogens (viruses)
Target of CD8 cells
On all cells
MHC class 2 expression
From extracellular pathogens
Target of CD4 cells
Present Ag to CD4s
Only on professional APCs
Gamma interferon can upregulate
Class 1 MHCs
Most individuals makeup of MHCs
Most are heterozygous because so many polymorphisms
MHC Class 1 structure
Alpha 1,2, and 3
B2-microglobulin there for stabilization
Alpha 1 and 2 have peptide binding groove
Alpha 3 inserted into membrane
MHC class 2 structure
No B2m
Has a Beta and alpha chain
b1 and a1 have peptide binding groove
Size of peptides MHC 1 vs 2
1 - small (8-9)
2 - large (18-23)
How do so few MHCs bind so many different antigens
Promiscuous binding specificity
There are a few anchor residues in each peptide…these are consistent throughout many peptides and are what allows binding to MHCs
Every T cell is
CD3 positive
Only let out TCRs that bind
MHC 1 and 2 but not too strongly
Most TCRs made of
Alpha and gamma subunits
Purpose of CD3
Signaling
Variability of TCRs found in
alpha chain
Ultimate signal translocation of many T-cells
IL-2 production to increase proliferation
Other type of TCRs
gamma delta in gut mucosa
TCR chromosomes
alpha and beta - 14
gamma - 7
What allows you to make so many different TCRs
Rag gene
MHC restriction is
Between TCR and peptide and MHC molecule
Can only bind on MHC and one peptide
Antigen processing
Intracellular degradation of antigens which are then bound to MHCs
Antigen presentation
Placement of antigenic peptide on the surface of APC to that it can be presented to TCR on T cell
Mechanism of antigen processing depends on
Location of infection AND type of APC
Class 1 synthesis
Protein antigen in cell, run through proteosome and degraded, passed to ER through TAP, becomes attached to MHC 1 and moves to membrane
Class 1 derived from
Cytoplasmic sources of antigen (intracellular)
Class 2 synthesis
Macrophage engulfs…MHC 2 and peptides fuse in vesicles and move to membrane
Antigen processing by B cells
Cell surface Ig binds to bacteria…engulfed and degraded…vesicles of MHC2 and peptides fuse and move to cell surface
CD8 and CD4 purpose
Make sure that T cell subsets bind to proper class of MHC
