Which cytokines activate NK cells?

• A. IL-4, IL-10
• B. IL-2
• C. IL-12, IFN-α, IFN-β
• D. TNF-α and IL-6

Answer: (C)

Cytokines that activate NK cells are signals from the innate immune response that boost their ability to kill virus-infected or stressed cells. IL-12 released by macrophages and dendritic cells tells NK cells to produce IFN-γ, which then activates macrophages and enhances the overall antiviral response. Type I interferons, IFN-α and IFN-β, directly prime NK cells to become more cytotoxic, increasing their granule content and killing capacity. This combination—IL-12 driving NK cells to secrete IFN-γ and type I interferons enhancing NK cell cytotoxicity—is the classic pathway that activates NK cells early in infection.

IL-2 can also support NK cells, but the strongest, most characteristic activators in this context are IL-12 along with IFN-α/IFN-β. On the other hand, IL-4 and IL-10 promote Th2 or anti-inflammatory environments rather than NK activation, and TNF-α with IL-6 are broad inflammatory cytokines that don’t specifically drive NK cell activation.