Which of the following is true of an IgG molecule:

Correct Answer: A

Rationale: IgG crosses the placenta; IgA has a secretory component , IgG has 2 sites , and IgM is pentameric (D, E).

Correct Answer: B

Rationale: Lymph nodes filter lymph to remove pathogens; they don't produce lymph , store blood , or secrete hormones .

Correct Answer: C

Rationale: The appendix is near the ileocecal valve; Peyer's patches are in the ileum, tonsils in throat, spleen in abdomen.

Correct Answer: A

Rationale: White pulp surrounds central arteries ; veins , capillaries , and lymphatic vessels are elsewhere.

Correct Answer: B

Rationale: Lymphocytes in white pulp respond to antigens; RBCs , macrophages , and platelets are in red pulp.