Lecture 8 Flashcards
where are peptides loaded in the MHCII pathway?
cytosol
what hematopoietic cell are MHC molecules NOT expressed on?
erythrocytes
why does MHCII assembly take 1-3 hours?
phagocytosis is a slow process
what activates proteases inside of the vesicles containing Ag?
decrease in pH
where are MHCII molecules synthesized? (HINT: same location as MHCI)
Rough ER
what is an invariant chain?
a trimer on MHCII that interacts with the peptide binding site to prevent binding while inside the RER
what class II molecule catalyzes the exchange of CLIP with the peptide
HLA-DM
what accidental process can cause an MHCI peptide to get loaded onto an MHCII molecule?
autophagy
what accidental process can cause an MHCII peptide to get loaded onto a MHCI molecule?
cross-presentation
how can viruses block Ag presentation to cytotoxic T-cells?
contain proteins called immunoevasins
what type of Ag is presented to gamma-delta T cells?
nonpeptide Ag
what molecules present the nonpeptide Ag?
CD1 molecules
MHC genes are highly ___________
polymorphic
Is there lots or little recombination amongst MHC genes?
LITTLE
why is there little recombination among MHC genes?
they are tightly linked and many alleles exist at each locus
how are MHC alleles inherited?
as two sets: one from mom and one from dad
the expression of MHC alleles is __________
codominant
define haplotype
the particular combination of MHC alleles on a single chromosome
what upregulates MHCII and MHCI?
CIITA (MHC class II transactivator)
what triggers CIITA to respond?
presence of IFN-gamma
exposure to _________ selects for MHC polymorphism
pathogens
