A living microbe with reduced virulence that is used for vaccination is considered:

Correct Answer: D

Rationale: Attenuated microbes are live, weakened for vaccines; toxoids are inactivated toxins.

Correct Answer: D

Rationale: Pattern recognition receptors (PARs) are genomically determined to bind to molecules widely expressed by microbes but not by host cells. Consequently, PARs cannot recognize host-associated molecules such as MHC class I molecules or cells of host origin such as B, T, or natural killer lymphocytes.

Correct Answer: C

Rationale: IgE is the least prevalent, primarily involved in allergies and parasite defense.

Correct Answer: A

Rationale: Large granular lymphocytes are NK cells, not T cells, which are typically smaller.

Correct Answer: C

Rationale: MHC-I is on all nucleated cells; MHC-II is on APCs, receptors (A, B) are specific.