In the processing and presenting of an exogenous antigen, when do the class II major histocompatibility complex (MHC-II) molecules merge with the vesicles containing the antigen peptide fragments?
A) during the formation of a phagolysosome containing the antigen
B) after the MHC-II molecules are packed into vesicles
C) before the MHC-II molecules are packed into vesicles
D) before the antigenic protein is split into peptide fragments
E) during the fragmentation of the antigenic protein

Question

Quizplus · Accepted Answer

After the MHC-II molecules are synthesized in the endoplasmic reticulum, they are packed into vesicles. These vesicles then merge with other vesicles containing the antigen peptide fragments that have been processed in the endocytic pathway, allowing the MHC-II molecules to bind to the peptide fragments before being presented on the cell surface.

In the Processing and Presenting of an Exogenous Antigen, When