Rescue of HDLM-2 cells from CD95 death receptor–induced apoptosis. Top panel: HDLM-2 cells were left untreated or treated with 10 or 20 ng/mL of the agonistic CD95 antibody CH-11 (□) or the respective IgM control (■) together with the indicated amounts of rhIL-21 for 20 hours. Thereafter, cells were pulsed with 0.037 MBq (1 μCi) [³H]-thymidine per well for a further 20 hours, and [³H]-thymidine incorporation was determined. cpm indicates counts per minute. Error bars denote SD. Bottom panel: cells were treated as described for panel A. After 48 hours, the percentage of apoptotic cells was determined by annexin V–FITC/PI staining and FACS analysis. Shown is the percentage of viable, annexin V–FITC/PI⁻ cells. Error bars denote SD; P values were calculated using the Student t test. All assays were performed in triplicate.