Individuals or mice with defects in the biochemical pathways needed for loading peptides onto MHC molecules show greatly increased susceptibility to virus infections. Experiments examining the MHC molecules present on the surface of host cells in these individuals would show:

Correct Answer: B

Rationale: Peptide loading defects (e.g., TAP) reduce MHC surface expression ; empty MHC or self-peptides are unstable.

Correct Answer: B

Rationale: Inflammation clears pathogens and starts tissue repair, a nonspecific process, unlike antibody production or cell-mediated responses (adaptive immunity).

Correct Answer: C

Rationale: Activated T cells (e.g., cytotoxic T cells) target intracellular pathogens, like viruses in infected cells, not extracellular pathogens or mediators.

Correct Answer: A

Rationale: Lymphocytes (B and T cells) are not phagocytic, focusing on adaptive immunity, unlike neutrophils, dendritic cells, and macrophages.

Correct Answer: C

Rationale: Plasma cells, differentiated B cells, secrete large antibody quantities, unlike T cells or thymocytes (immature T cells).