10 - Antigen Processing and Presentation Flashcards
Which pathway are endogenous antigens processed by and which MHC molecule is it presented on?
cytosolic/enodgenous pathway | MHC class I
Which pathway are exogenous antigens processed by and which MHC molecule is it presented on?
exogenous pathway | MHC class II
MHC class I interact with peptides derived from?
cytosolic degradation of endogenously-synthesized proteins
MHC class II interact with peptides derived from?
endocytic degradation of exogenous antigens
What is the secretory pathway? What are the 3 places products in this pathway end up at?
intracellular pathway | take cytosolic proteins and package them into intracellular vesicles to either be: secreted, on the surface, or in lysosomes | endogenous antigen
What is the endocytic pathway?
taking something up (endocytose) and target it into endosome and lysosome for degradation | exogenous antigen
What are the 2 methods in which the amount of each type of protein inside a cell is regulated by?
protein degradation | synthesis of new proteins
What are the 2 organelles in which proteins are degraded in?
lysosome | proteosome
What are the protease complexes that generate the peptides that associate with MHC I?
proteosomes
What is an immunoproteosome?
proteosome = more efficient at cutting up proteins to specific fragment length needed to bind to MHC I
What is the function of proteosomes?
recognizes and degrades ubiquitin-tagged intracellular proteins
Where are immunoproteasomes found and which cells can activate them?
all nucleated cells | by APCs
What is the role of chaperones in the endogenous pathway? What is one key chaperone mentioned?
helps with protein folding in the ER | folds MHC I molecule and ensures peptide is bound to MHC I | calnexin
What is the function of the TAP protein?
shuttles cytosolic peptides into the lumen of RER
What are the 3 ways that extracellular antigens can get into intracellular vesicles?
actin-mediated phagocytosis | receptor-mediated endocytosis | autophagy
Where are the internalized antigens that will associated with MHC II found?
endosome
How do B-cells take extracellular antigens up into itself?
receptor-mediated endocytosis
What allows for the dissociation of the peptide from the receptor?
drop in pH in the late endosome
What is the role of the invariant chain (li)?
associates with MHC II in ER lumen = blocks MHC II peptide binding site to ensure that MHC II won’t get loaded with peptides for MHC I
What is CLIP?
protein blocking peptide binding groove after invariant chain is degraded
What is HLA-DM?
exchanges CLIP out for the processed exogenous peptide to bind on MHC II
How is the invariant chain degraded?
via proteolytic activity
What is Cross-Presentation of exogenous antigens
a way for MHC I to present an exogenous peptide | exogenous antigens are redirected to the endogenous presentation pathway
What is the purpose of the Cross-Presentation of exogenous antigen? Why does it need to be presented on MHC I and not on MHC II?
to activate CD8 T-cells | normal cells cannot activate CD8 T-cells, only APCs
Which cells can activate CD8 T-cells?
APCs
Which cell carries put cross-presentation?
ONLY dendritic cells
