Major histocompatibility Flashcards
Human leukocyte antigens
Tightly linked cluster of cell surface glycoproteins that regulate immune cell interactions
How many loci of HLA are there?
Three
Class I loci
HLA-A, B, and C that are present on nearly all cells and present to CD8+ cells
Class II loci
HLA-D (DR, DQ, DP); found on dendritic cells, macrophages, monocytes, and B cells and present to CD4+ cells
Class III loci
They happen to be in the area but don’t present to T cells
What do each of the HLA in class I code for?
A polypeptide of about 44,000 daltons
When these cells are on the membrane, with what other component do they associate?
Associate non-covalently with beta-2 microglobulin that is coded by a separate gene
Extracellular domains on the alpha chain
Three different domains; alpha-1, 2 and 3. Alpha-3 interacts with the beta-2 microglobulin
What percentage of the alpha chain is carbohydrate?
10%
Compare the length of amino acids bound by each of the classes of MHC.
Class I: 8-10
Class II: 13-17
How large are the alpha and beta chains in MHC class II?
Alpha: 34,000 daltons
Beta: 29,000 daltons
Anchor residues for MHC
Related amino acids (that don’t need to be the same) which help bind to the receptor
Codominance of MHC expression
Everyone displays an equal number of MHC I and MHC II complexes; 3 maternal and 3 paternal class I, as well as 3 maternal/ 3 paternal class II
What do the amino acid sequence differences allow?
Peptide binding and T cell recognition
MHC restriction
The dependence of T cell reactivity on not only the antigen alone, but on the presence of the antigen in the context of the MHC
