The complement system's lectin pathway is triggered by:

Correct Answer: B

Rationale: The lectin pathway uses mannose-binding lectin; antibodies are classical, cytokines signal, histamines inflame.

Correct Answer: A

Rationale: The pancreas is a digestive and endocrine organ, not a lymphatic organ; spleen, thymus, and tonsils are part of the lymphatic system.

Correct Answer: C

Rationale: Primary nodules contain inactive B-lymphocytes; secondary nodules have active ones.

Correct Answer: C

Rationale: Spleen filters blood , forms blood in fetal life , destroys RBCs and has immune functions ; lymphocyte formation in germinal centers is more lymph node-specific (C is less accurate).

Correct Answer: C

Rationale: Microglial cells are macrophages in the central nervous system (CNS).