Dendritic cells in the skin, known as Langerhans cells, express very high levels of the NOD-like receptor, NLRP3. Previous studies showed that treatment of these cells with the Staphylococcus aureus pore-forming toxin causes K⁺ efflux from the cells. The explanation for these results is:

Correct Answer: C

Rationale: Live S. aureus activates TLR and NLRP3 for IL-1; toxin alone (K⁺ efflux) needs a second signal, membranes lack full stimuli.

Correct Answer: C

Rationale: The stirrup (stapes) in the middle ear amplifies sound vibrations, while the eardrum transmits and the anvil (incus) transfers them, but amplification is primarily by the stapes.

Correct Answer: D

Rationale: Antibodies have two antigen-binding sites, not one, making D false; the others are true about antigen-antibody interactions.

Correct Answer: C

Rationale: Mast cells release histamine in allergic reactions, causing symptoms like swelling, not interferon, allergens (triggers), or perforin.

Correct Answer: A

Rationale: Pleiotropic cytokines (e.g., IL-6) have multiple effects on various cells, unlike autocrine (self-acting), synergistic, or antagonistic.