Question

Correct sequence of events in cytosolic pathway of antigen presentation:

• A. C, B, D, A and E
• B. C, A, D, E and B
• C. C, A, E, D and B
• D. C, D, A, E and B

Hint:

Cytosolic pathway = MHC Class I = Intracellular pathogens. Proteasome is the “shredder” that starts it all.

Answer 1

The Correct Option is D

Step 1: Concept
The cytosolic (endogenous) pathway processes antigens for presentation on MHC Class I molecules. Step 2--3: Analysis
Endogenous antigens are degraded by proteasomes (C). MHC Class I chains bind to calnexin (D). Calnexin dissociates and MHC associates with calreticulin and tapasin (A). MHC captures peptides (E). Peptides are transported into the RER via TAP (B).

Step 4: Conclusion
The correct order is C $\to$ D $\to$ A $\to$ E $\to$ B.

Final Answer: (D)