Antigen Processing and Presentation Flashcards
B cells and their product: antibodies…
recognize extracellular antigens or those found or exposed on the outside of a cell
- neutralization
- activate complement
- enhance phagocytosis
it is a job of the T lymphocyte to recognize…
intracellular antigens
in order for T cells to recognize antigens derived from within a host cell the antigen must be processed.
exogenous antigen processing pathway
HLA class II molecules are involved
activation of CD4+ T helper cells
in order for T cells to recognize antigens derived from within a host cell the antigen must be processed.
endogenous antigen processing pathway
HLA class I molecules are involved
activation of CD8+ cytotoxic T cells
nearly every vertebrae has an MHC that encodes genes responsible for determiniation of
self v nonself
Genes fro MHC are tightly linked on
chromosome 6
each person possesses two sets of MHC genes
there are 6 main loci on chromosome 6:
HLA Class I: HLA-A, HLA-B, HLA-C
HLA class II: HLA-DP, HLA-DQ, HLA-DR
MHC genes belong to the
Ig (“antibody”) supergene family
Common characteristics of HLA molecules
- variable amino acid sequence in peptide binding groove (presents peptide to T-cell)
- binding site for a co-receptor on T cells (CD8/CD4)
- transmembrane glycoproteins which activate signaling molecules
Uncommon characteristics of HLA molecules
- Structure: class I is monomer and class II is dimer
- structure: class I have beta2 macoglobulin (chaperone protein helps it to ‘stand up’)
- T cell interactions: class I with CD8 and class II with CD4
- expression: class I in all cells in body and class II in antigen presenting cells
unlike B cells, T cells recognize and respond only to antigens bound on
HLA molecules - “MHC restricted” or “HLA restricted”
CD4+ T helper cells recognize
HLA Class II plus processed peptide
CD8+ cytotoxic T cells recognize
HLA class I plus processed peptide
HLA class I is found
on all nucleated cells
