NKp30 co-stimulation increases STAT signaling in the presence of IL-12. Purified human peripheral blood NK cells were stimulated as indicated for 48 h. Cytokines were supplemented at the beginning of the cell culture in U-shaped 96-well plates. n = number of donors. Mean ± SD. Paired t test, parametric; *, P < 0.05; **, < P < 0.01. IL-12^low = 2.5 ng/ml. IL-2^low = 3 U/ml. (A) Cell signaling (pS6^S235/236, pSTAT4^Y693, pSTAT5^Y694) of 48-h-stimulated NK cells. IFNγ secretion was used as a positive control for IL-12 stimulation (two independent experiments). (B) IL-12Rβ2 or NKp30 protein expression levels following IL-2–mediated priming. Data are normalized to minimize variations between donors. n = 3 (three independent experiments).