Ex vivo hyporesponsiveness of NK cells from SHIP^−/− mice. Intracellular IFN-γ (A) and CD107α (B) in NK cell populations (NK1.1⁺CD3⁻ in the lymphocyte gate) from total splenocytes incubated with a mix of IL-12 and IL-18 or PMA and ionomycin (P/I) for 6 hours. Data are pooled from at least 3 independent experiments. Error bars indicate SEM.