7- Major Histocomatibility Complex Flashcards
Major Histocompatibility Complex
Set of closely linked genetic loci that have been found to be overwhelmingly important in determining the fate of engrafted tissue.
Very important for physiological function of the immune system. Prime function is presentation of peptides to T lymphocytes.
What is the MHC known as in humans?
HLA: Human Leukocyte Antigen Complex (HLA Complex)
Classes of HLA Complex
Class I Loci: HLA-A, B, and C
Class II Loci: HLA-D (DR, DQ, DP)
Class III Loci (not important in antigen presentation)
Class I vs II
I = 1 polypeptide chain; present small peptides. INTERACTS WITH CD8 T LYMPHOCYTES
II = 2 polypeptide chains (alpha and beta chains); present larger peptides. INTERACTS WITH CD4 T LYMPHOCYTES
Very similar structures
What chain do Class I Loci Molecules always associate with?
Beta-2 macroglobulin aka light chain
What’s necessary for a peptide to bind to an MHC Class 1 molecule?
For the anchor residues of the peptide to be highly conserved. Many peptides can be presented by a specific class I molecule, as long as they have this conserved portion.
Where are class I molecules found? class II?
I: All nucleated cells
II: All antigen presenting cells (macrophages, dendritic cells, etc.)
Codominance and MHC cells
MHC cells are expressed codominantly.
Each individual expresses 3 paternal and maternal class I molecular types, for class I and the same for class II.
Where are MHC Genes highly polymorphic?
The peptide binding cleft, where foreign antigen is presented. This allows for fighting against mutable pathogens.
MHC Restriction
The dependence of T cells specific reactivity on foreign Ag plus MHC products rather than on foreign Ag alone. MHC molecule is VERY specific.
One MHC can bind many types of antigen, but one T cell can only bind a specific MHC (2 alpha helices), antigen combination.
Eliciting of Cytoxic T Lymphocytes
They are elicited by host cells that are virus infected and are CARRYING FOREIGN Ags.
