Major Histocompatibility Complex Lecture Flashcards
The major histocompatibility complex (MHC) was discovered through
transplantation studies
Products of genes in the MHC region of the genome are responsible for
rapid rejection of tissue grafts
MHC are
polymorphic
each common variant of a polymorphic gene is called an allele
syngeneic
inbreed sibling mice for around 20 generations-offspring genetically identical- will accept others tissue grafts
inbred strain
allogeneic
different inbred strains- will not accept tissue grafts from another inbred strain
Congenic
identical at all loci except the trait that you select, and for which you bred them
developed by a cross between 2 inbred straisn
MHC genes control
allograft rejection
MHC’s real job
present Ag epitopes to TCRs and are recognized together with the epitopes by the TCR
2 classes of MHC molecules
class I
Class II
Both classes of MHC are
polymorphic
structurally distinct but homologous proteins
MHC classes are _____ expressed
co-dominantly expressed
Co-dominant expression
products of the alleles on each chromosome are expressed on a cell at the same time
A gene on a chromosome is a
haplotype
Class I molecules present epitopes to
CD8+ T cells
Class I molecules are expressed on
all nucleated cells on the body
Class II molecules present epitopes to
CD4+ T cells
Class II molecules are expressed on
APCs: Macs, Dendritic cells, B cells
often differentially regulated
each MHC molecule consists of
extracellular, peptide-binding groove and is anchored through a transmembrane and cytoplasmic domain
Polymorphism of MHC molecules is due to
AA residues in and adjacent to the peptide-binding groove
Non-polymorphic, extracellular lg domains contain
binding sites for the T cell surface “markers” CD4 or CD8
Each class I or class II molecule has a single
peptide binding cleft that can accommodate many different peptides
epitopes that trigger specific T cells compete with
each other for MHC molecule binding cleft
MHC molecules present peptide Ags from
different cellular locations
Class I molecules present peptides from where
cytosol
Class II presents peptides from
extracellular
Class I molecules are _____ expressed on
constitutively
essentially ALL nucleated cells
Class II are usually expressed only on
Antigen Presenting Cells
Class II expression is up-regulated by
cytokines during both innate and adaptive immune responses
