Protection of CD95-induced apoptosis by CD95 blocking MoAb ZB 4. The activated PBMC of patient no. 11 were preincubated with ZB 4 (500 ng/mL for 60 minutes) and then exposed to anti-CD95 for 48 hours. The cells were incubated with 50 μg/mL of PI for 30 minutes at room temperature, after fixation overnight with 70% ethanol, and the DNA content was analyzed using flow cytometry. Histograms on the left, center, and right represent the results after incubation with serum alone, anti-CD95, and ZB4 + anti-CD95, respectively. The percentage of apoptotic cells is indicated on the left side of each panel.