is largest, single intra-abdomin organ

Correct Answer: D

Rationale: The spleen is the largest single intra-abdominal lymphatic organ; the liver is larger but not lymphatic.

Correct Answer: C

Rationale: Paracortex venules are lined with cuboidal (high) endothelium ; it's T-lymphocyte-rich, not B , and not between spleen structures or lined with plasma cells .

Correct Answer: A

Rationale: NK cells are innate immune cells from a lymphoid progenitor; they're not adaptive (C, D) and not myeloid-derived .

Correct Answer: B

Rationale: PRRs (pattern recognition receptors) recognize PAMPs and DAMPs as danger signals ; C is a subset, A and D are incorrect.

Correct Answer: A

Rationale: CD40L (on Th cells) prolongs DC survival ; binding , proliferation , and TCR activation are indirect or separate.