CH. 8: MHC Flashcards
What is the role of MHC in antigen presentation?
to bind to peptides and be recognized at cell surface by specific TCR
Describe polygenicity and polymorphism.
- polygenicity: coded for by multiple independent genes
- polymorphism: multiple stable forms of each MHC gene existing in population
Which genes code for MHC classes I and II?
- MHC class I: HLA-A, HLA-B, HLA-C
- MHC class II: HLA-DP, HLA-DQ, HLA-DR
Describe the structure of MHC class I. Which domains are paired with which?
4 domains: a1, a2, a3, B2m
- a1 and a2 (forms peptide-binding groove)
- a3 and B2m
MHC class I: How long of a peptide can it hold? How many anchor residues? How many amino acids in peptide make contact with TCR?
- 8-9 amino acids long
- 2 anchor residues
- 1-4 amino acids
Which CD binds to the invariant regions of either MHC class I and II? Which domain?
MHC class I: CD8; a3 domain
MHC class II: CD4; B2 domain
Describe the structure of MHC class II. Which domains are paired with which?
4 domains: a1, a2, B1, B2
- a1 and B1 (forms peptide-binding groove)
- a2 and B2
- made of 2 chains: a and B
MHC class II: How long of a peptide can it hold? How many anchor residues? How many amino acids in peptide make contact with TCR?
- 12-17 amino acids long
- 4-5 anchor residues
- 4-6 amino acids
Describe cross-presentation.
- when peptides generate from exogenous protein antigens and present them to CD8+ cells; possibly due to tissues cells that are infected that are not taken up by APCs or response to dying cells
- endogenous antigens associated with MHC class II may occur; autophagy
Describe superantigens.
- exotoxins produced by pathogenic bacteria
- activates huge numbers of CD4+ T cells, which proliferate and secrete high levels of cytokines
- causes fever and cardiovascular shock; can be fatal
