Freshly isolated LGL are resistant to CD95 and anti-CD3–mediated apoptosis. CEM-sensitive cell line was used as a positive control for CD95-induced apoptosis (top panel). The cells were incubated with media alone (histograms on the left) or with anti-CD95 (CH11, 1 μg/mL) for 24 and 48 hours, as shown. The cells were then stained with 7-AAD and analyzed by flow cytometry. The LGL leukemic cells are analyzed in the bottom panel. The percentage of apoptotic cells is indicated in each histogram. Although leukemic LGL were resistant to both anti-CD95– and anti-CD3–induced apoptosis (BC3, 10 μg/mL), they remained susceptible to ceramide.