Lecture 16: MHC Genetics, Polymorphism and Restriction Flashcards
MHC molecules must be able to bind many different ________.
Recall the two faces of antigenic peptides.
Because they contribute little to binding, the residues pointing outside of the MHC can vary without compromising the strength of the MHC-peptide interaction: variable residues
MHC genes are ______________, which varies the structure of the peptide binding site.
Recall the implications of MHC polymorphism and polygeny.
Define the concept of polygeny
Recall the location of MHC genes in human and mouse chromosomes.
Each MHC ________ binds a set of peptides with a preferred combination of anchor residues.
allotype
T cells are selected in the thymus so that only those that can recognise _________ go to the circulation (positive selection).
self-MHC
T cells of each individual only recognize antigenic determinants presented by the _________________.
Recall the concept of alloreactivity and its effect on transplantation
In principle, alloreactive T cells might depend on recognizing either a foreign peptide antigen or the nonself MHC molecule to which it is bound for their reactivity against nonself MHC; these options have been called peptide dependent and peptide-independent allorecognition.
Most individuals will be ____________ for the genes encoding MHC class I and class II molecules. The particular combination of MHC alleles found on a single chromosome is known as an ____________. Expression of MHC alleles is ___________, meaning that the protein products of both of the alleles at a locus are expressed equally in the cell
Most individuals will be heterozygous for the genes encoding MHC class I and class II molecules. The particular combination of MHC alleles found on a single chromosome is known as an MHC haplotype. Expression of MHC alleles is codominant, meaning that the protein products of both of the alleles at a locus are expressed equally in the cell
Because of the polygeny of the MHC, every person expresses at least __________ different MHC class I and II molecules
Because of the polygeny of the MHC, every person expresses at least three different MHC class I and II molecules
The specificity of a T-cell receptor is defined both by the ________________ and by the _________________
The specificity of a T-cell receptor is defined both by the peptide it recognizes and by the MHC molecule bound to it
Recalll how positive selection may lead to alloreactive T cells.
When developing in the thymus, T cells whose T-cell receptors interact weakly with the self MHC molecules receive survival signals, and so are favoured for representation in the peripheral repertoire. It is thought that T-cell receptors that interact with one type of MHC molecule are more likely to cross-react with other (nonself) MHC variants.
