NK cells (Natural Killer cells)

Natural Killer (NK) cells are part of your innate immune system. They destroy virus-infected and cancerous cells without needing prior 'training' on an antigen. Their action is governed by a balance: activating receptors (NKG2D, NKp46, DNAM-1) versus inhibitory receptors that recognize your own healthy cells (via self-MHC class I). NK cells also help direct the adaptive immune system, by quickly releasing cytokines, especially IFN-γ. With age, your NK-cell numbers in the blood tend to rise. But the cells shift toward a 'terminally differentiated', less proliferative state, with weaker killing per cell and poorer cytokine output. That functional decline means worse tumor surveillance and weaker control of reactivating herpesviruses in older adults.

Last reviewed: June 22, 2026

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