L09: Antigen Processing and Presentation

Question 1

MHC I processing:

Answer 1

• MHC I peptides synthesized in RER
• calnexin as a chaperone
• B-microglobulin then added removing calnexin
• Then association with calreticulin, tapasin and ERp57
• TAP protein binds antigen to MHC molecule then all chaperones release, and MHC heads to golgi, then sent via exocytosis to PM

Question 2

MHC II processing:

Answer 2

• also synthesized in ER but doesn’t encounter antigen there
• in the golgi it meets with the invariant chain
• Then targeted to early endosome (invariant chain is degraded to CLIP here)
• When CLIP is removed, MHC II binds antigen, is stabilized and targeted to the PM