To determine if the phenotypic activation and proliferative differences between NKR‐P1A+ and NKR‐P1A‒ subsets of NKG2C+ NK cells in CMV seropositive individuals may also influence their response to stimuli, we assessed IFN‐γ production (IFN‐γ+) and degranulation (CD107a+) in NK cells stimulated with PMA and Ionomycin (PMA/I) or K562 tumor cells in vitro. The gene discussed is KLRB1; the disease is neoplasm.