Reduced apoptosis by mature splenic NK cells from BCAP^−/− mice. (A) Fresh splenic lymphocytes were incubated overnight at 37°C in either medium alone or medium containing IL-2. After incubating overnight (18 hours), the cells were stained with anti-NK1.1, anti-CD3ϵ, and annexin V, then analyzed by flow cytometry. Results for BCAP^−/− samples are represented by a thicker line. Percentages of apoptotic BCAP^−/− (KO) and wild-type (WT) cells in the gated regions are shown. Top panels are cells incubated overnight in medium alone, middle panels show cells incubated overnight in medium with IL-2, and cells incubated overnight with IL-2, then 24 hours without IL-2 are shown in the bottom panel. (B) Fresh splenic lymphocytes were incubated in the absence of IL-2 for 3 hours at 37°C with or without 5 μM staurosporine, then stained with anti-NK1.1, anti-CD3ϵ, anti-CD11b, annexin V, and anti-Ly49I. Values are means plus or minus SD of 6 WT and 6 BCAP^−/− mice (*difference with P < .01).