Flow cytometry results showing that leukemic LGL are susceptible to anti-CD95–induced apoptosis after activation. The PBMC of patient no. 4 were cultured initially with PHA (1 μg/mL) for 2 days and then with IL-2 (100 U/mL) for 10 more days. The cells were then stained with CD57⁺ and sorted on FacStar. The purified CD57⁺ cells (94%) were then incubated with anti-CD95 MoAb (CH11, 1 μg/mL) for 48 hours and stained with 7-AAD before analysis using flow cytometry. The graph on the left represents the control (media alone); the graph on the right represents the cells incubated with CH11. The percentage of apoptotic cells is shown on the upper-right quadrant.