The drawing in Figure Q4.12 shows antibodies bound to repetitive epitopes on the surface of a bacterial pathogen. Even though all of these epitopes are identical, not all of them have antibodies bound to them. The most likely explanation for this failure of antibodies to bind to every possible epitope on the surface of the pathogen is:

Correct Answer: C

Rationale: Steric hindrance limits binding to all epitopes; insufficient antibody , evasion , or dual-site binding are less likely.

Correct Answer: C

Rationale: Histamine is released by damaged cells (e.g., mast cells) to initiate inflammation, unlike interferon (antiviral), complement (immune enhancement), or antihistamine (blocks histamine).

Correct Answer: A

Rationale: Monoclonal antibodies come from hybridomas (B cell-tumor cell fusions), producing identical antibodies, not from pregnancy, infection, or B-T cell fusion.

Correct Answer: D

Rationale: C3a and C5a are anaphylatoxins that trigger inflammation by recruiting immune cells, not forming MAC (C5b-C9) or opsonizing (C3b role).

Correct Answer: A

Rationale: MHC diversity arises from codominant expression of alleles from both parental haplotypes, enhancing antigen presentation variety.