Question

Peptide brought in from outside (extracellular) loaded onto:

A) MHC class I
B) MHC class II
C) MHC class III
D) MHC class IV

Answer 1

Extracellular antigens are loaded onto MHC class II molecules and presented to T cells on the cell surface.

Step-by-step explanation:

The correct answer is MHC class II.

Extracellular antigens, such as those from bacteria and parasites, are brought into the endomembrane system of cells through receptor-mediated endocytosis. The resulting vesicle fuses with vesicles from the Golgi complex, which contain pre-formed MHC class II molecules. After fusion and association of the antigen and MHC, the new vesicle makes its way to the cell surface, where the MHC class II molecules present the antigen to T cells.