Flashcards in Week 7 Reading Chapter 6 124-134 Deck (14):
What types of peptides are loaded onto MHC I
Cytosolic peptides are loaded onto MHC I and recognized by CD8+, while extracellular peptides that are uptaken are recognized by MHC II and recognized by CD4+
How does Interferon gamma improve MHC presentation?
Interferon mediates the conversion of the constitutive proteasome to the immunoproteasome (changes beta chain to LMP2, LMP7, MECL-1); also increases the rate at which MHC molecules are transcribed.
Dimeric protein that is responsible for the transport of peptides from the cytosol into the ER; ATP dependent;
located in the ER; binds to TAP and MHC I and brings them together. Aids in peptide loading; once peptide is bound tapasin dissociates
What chaperone proteins are responsible for the folding and stability of MHC I a chain?
Calnexin (also responsible for folding and assembly of MHC II) and calreticulin.
ER resident aminopeptidase; further trims peptides to fit into MHC I binding cleft
What are the two reasons Class II MHC is not loaded with peptides while they are in the ER?
1) because they do not associate with TAP 2) Because invariant chain blocks peptide binding.
What cell types uptake extracellular pathogens for loading on MHC II?
DCs, macrophages, B Cells
Ii; promotes folding and assembly of Class II MHC molecules to the late endosomes and lysosomes; blocks peptide binding cleft
What enzymes mediate the removal of Ii from MHC II?
Cathepsins and HLA-DM
Class II associated invariant chain peptide; remnant of Ii post proteolytic cleavage of Ii; blocks antigen binding
MHC encoded enzyme responsible for the removal of CLIP; adds other peptides to MHC II; tests for the highest affinity peptide
Exception!!: some DCs have the ability to capture an to ingest virus infected or tumor cells and present viral or tumor antigens to naive CD8+ T lymphocytes; phagosomes fuse with ER; proteins are translocated from ER to cytosol