Septic shock is a serious, often fatal response to an infection in the bloodstream. This response can be elicited in mice by intravenous injection of bacterial LPS. However, it was found that one strain of mice, C3H/HeJ, is resistant to LPS-induced shock. This fact was used to clone the gene for TLR-4 based on positional cloning from C3H/HeJ mice. Another example of a strain of mice that is resistant to LPS-induced septic shock is:

Correct Answer: A

Rationale: TNF-receptor-deficient mice resist LPS shock as TNF drives inflammation; TLR-2 targets other PAMPs, LFA-1 or neutrophils are secondary.

Correct Answer: B

Rationale: Innate defenses are nonspecific and include physical barriers like dead skin cells and mucus, which prevent pathogen entry, unlike antibodies or memory cells (adaptive immunity).

Correct Answer: C

Rationale: B cells, upon antigen binding, differentiate into plasma cells that produce antibodies, not dying, engulfing, or altering antigens.

Correct Answer: A

Rationale: The antigen-binding site is at site A (assumed figure), located at the variable regions of the antibody's arms.

Correct Answer: C

Rationale: Mature DCs form dendrites to present antigens to T cells, unlike immature DCs (uptake) or granulocytes (not primary targets).