Major Histocompatibility Complex Flashcards
what do B cells need to switch antibody class, make high affinity antibodies, or become memory B cells?
help from T cells
to become activated through the BCR binding to the extracellular antigen
are antibodies generally effective against intracellular pathogens?
no
what cells in adaptive immunity destroy infected host cells?
cytotoxic T cells
when will a cytotoxic T cell interact with an intracellular antigen?
when a fragment of the antigen (antigenic peptide) is on the surface of a host’s cell bound to a major histocompatibility complex
the phenomenon of T cells recognizing an antigen only in association with self-MHC molecules is called ___________
MHC restriction
why are two classes of MHC molecules needed?
Tc cells are MHC class I-restricted
Th cells are MHC class II-restricted
the MHC acronym for dogs is ___ and the acronym for horses is ___ and the acronym for caprines is ___
DLA
ELA
CLA
each MHC class I molecule consists of a ________________________________ and a ____________________
large transmembrane glycoprotein alpha chain
much smaller beta-2 microglubulin
what are the domains of the alpha chain? which ones are variable and which ones are constant?
alpha-1: variable
alpha-2: variable
alpha-3: constant
what forms the peptide binding groove or peptide binding cleft in MHC I?
parts of the alpha-1 and alpha-2 domains
is the peptide binding groove/cleft of the alpha chain closed at both ends or open at both ends?
closed at both ends so can only fit peptides 8-10 amino acids long
the amino acid differences between the MHC products are confined principally to the sites in the _______________
peptide binding groove where the antigenic peptide binds
what glycoprotein do cytotoxic T cells express on their surface and what domain does it bind to?
CD8 binds to the alpha-3 domain of MHC I
what is the beta-2 microglublin?
invariant polypeptide that provides stability to the MHC class I molecule
without it, alpha chain does not express on cell surface
what makes up the MHC class II molecule?
an alpha and a beta chain, each with two domains
what folds into the peptide binding groove or cleft in the MHC class II molecule?
alpha-1 and beta-1 domains (these are the polymorphic ones)
what is the peptide binding groove/cleft like in the MHC class II molecule?
open at both ends
large peptides fit: 12-20 amino acid residues
what glycoprotein do helper T cells express on their surface to bind the beta-2 domain of MHC II?
CD4
on what cells are MHC class I molecules expressed?
almost all nucleated cells
most highly expressed on lymphocytes and specialized antigen presenting cells
MHC class II molecules are expressed on __________________________
only specialized antigen presenting cells
what molecules play a role in T cell development in the thymus and T cell activation in the secondary lymphoid organs?
MHC proteins
what are the undesired functions of MHC molecules?
transplant rejection
certain autoimmune or inflammatory diseases
when there are no foreign antigens present, what happens with MHC class I and II peptide binding grooves?
they are loaded with peptide fragments derived from the body’s own proteins: self-antigens
when is the presentation of self-antigens important?
development phase of T lymphocytes in the thymus
true/false: the peptide binding groove is formed by alpha-1 and alpha-2 of MHC class I
true
true/false: expression of MHC class I, but not MHC class II molecule, is much greater in dendritic cells than in macrophages
false: both expressed at greater rate on dendritic cells than on any other antigen presenting cells
what does CD4 bind with?
beta-2 domain of MHC class II molecules
