NK cells express receptors from several families, each of which has multiple members. Some of these receptors are activating and others are inhibitory, and NK cell activation is dependent on the balance of signaling overall. The individual NK cells in an individual:

Correct Answer: C

Rationale: NK cells express a subset of receptors for balanced signaling; not always activating , not just cytotoxic , and are ILCs .

Correct Answer: A

Rationale: Elevated interferon levels indicate a viral infection, as it's a specific antiviral response, not related to cancer, diet, or monocyte differentiation.

Correct Answer: D

Rationale: Mammalian antibodies have five classes (IgM, IgG, IgA, IgE, IgD), not two, making D false; others are true.

Correct Answer: C

Rationale: AMPs primarily perforate bacterial membranes to cause lysis, targeting prokaryotes, not enhancing phagocytosis or binding eukaryotic membranes.

Correct Answer: B

Rationale: MHC1 is on all nucleated cells, presenting processed peptides (8-10 aa) to CD8+ T cells, not CD4+.