The specificity of an antibody is due to

Correct Answer: D

Rationale: The variable portion of heavy and light chain determines specificity by forming the antigen-binding site, unlike the Fc portion (effector function).

Correct Answer: B

Rationale: IgA is predominant in milk for mucosal protection; IgG is in blood, IgM and IgE are less relevant.

Correct Answer: D

Rationale: All (A, B, C) are true: IgE (Type I), complexes (Type III), and complement/IgG (Type II); thus, D.

Correct Answer: D

Rationale: TNF-α upregulates adhesion molecules; it increases permeability , not decreases.

Correct Answer: B

Rationale: Lymph nodes produce lymphocytes and filter debris/particles, but plasma proteins are made by the liver.