Question

MHC class I molecules present peptone antigens derived from a _______ compartment, whereas MHC class II molecules present peptide antigens derived from a _______ compartment.

A. extracellular; intracellular
B. intracellular; extracellular
C. opsonization; neutralization
D. neutralization; opsonization
E. none of the above

Answer 1

MHC class I molecules present intracellular antigens, while MHC class II molecules present extracellular antigens.

Step-by-step explanation:

MHC class I molecules present antigen derived from an intracellular compartment, while MHC class II molecules present antigen derived from an extracellular compartment.

Intracellular antigens, such as viruses and certain bacteria, are processed in the cytosol by the proteasome and then brought into the endoplasmic reticulum by the transporter associated with antigen processing (TAP) system. They interact with class I MHC molecules and are eventually transported to the cell surface.

Extracellular antigens, such as bacteria and parasites, are brought into the endomembrane system of the cell by receptor-mediated endocytosis. The resulting vesicles fuse with vesicles from the Golgi complex, which contain pre-formed MHC class II molecules. After fusion, the new vesicles make their way to the cell surface.