Antigen presenting cells (APCs) include macrophages and dendritic cells, which are found in lymphoid tissues and the These are critical in the uptake and presentation of antigen to T cells.

Correct Answer: C

Rationale: APCs like macrophages and dendritic cells are abundant in the skin, a key site for pathogen entry, and lymphoid tissues, where they present antigens to T cells.

Correct Answer: A

Rationale: Macrophages are specialized for phagocytosing and degrading particulate antigens, presenting them to T cells.

Correct Answer: D

Rationale: Class II MHC is primarily on professional APCs (B cells, macrophages, dendritic cells), making d (moved from e) correct.

Correct Answer: D

Rationale: T cells recognize linear peptide epitopes presented by MHC, not discontinuous ones, which antibodies can bind.

Correct Answer: D

Rationale: The full antibody includes both Fc and Fab regions, unlike isolated fragments.