Anti-Fas antibody ZB4 inhibits Fas-mediated apoptosis but not etoposide- or doxorubicin-induced apoptosis. Wild-type Jurkat cells were incubated with 1 μg/mL ZB4 for 30 minutes before addition of 100 ng/mL 7C11 anti-Fas antibody, the indicated concentration of etoposide or doxorubicin, or incubation on a plate coated with anti-CD3 as described.38 After incubation for 3 hours (7C11 anti-Fas antibody), 6 hours (etoposide), or 24 hours (anti-CD3 or doxorubicin), cells were stained with propidium iodide and analyzed by flow cytometry. The percentage of hypodiploid cells is graphed. (▪), without ZB4; (□), with ZB4.