BCAP^−/− NK cells exhibit enhanced immune functions. (A) Cytotoxicity response by freshly harvested wild-type (▴) and BCAP^−/− (●) NK cells against CHO-K1 targets. Splenocytes were apportioned into wells along with target cells to achieve the stated effector (CD3⁻, NK1.1⁺) to target ratio. The data shown represent the means plus or minus SE of 3 separate experiments. In some cases, the error bars are smaller than the data point icon. P values were calculated by a 2-tailed Student t test. (B) Cytotoxicity against YAC-1 targets by freshly isolated NK cells from mice prestimulated with poly I:C. The data shown represent the means plus or minus SE of 2 separate experiments. (C,D) Cytotoxicity against YAC-1 by sorted and IL-2 cultured NK cells (1000 U/mL) for 7 days (C) or 15 days (D) The data shown represent a single experiment but are representative of at least 3 experiments that were performed under similar conditions. (E) IFN-γ response by stimulated NK cells. Splenic lymphocytes were cultured for 5 hours with or without combinations of 500 U/mL IL-2, 10 ng/mL IL-12, and plate-bound anti-NK1.1. Brefeldin A (10 μg/mL) was added after the first hour. Stimulated BCAP^−/− NK cells are shown as a thick line, stimulated wild-type cells as a thin line, and the unstimulated wild-type control as a thin dashed line (< 1% IFN-γ⁺). Percentages of IFN-γ⁺ NK cells are indicated. Data are representative of at least 3 experiments.