Lymphoma B cells are resistant to CD95-mediated apoptosis in an assay detecting late stages of apoptosis. Jurkat cells (□) and three lymphoma cell populations isolated from LCL-4 (▴), MCL-6 (⧫), and DLCL-1 (•) patients were labeled with [⁵¹Cr]-sodium chromate and then incubated with increased concentrations of anti-CD95 MoAb CH-11 for 4 hours. The apoptosis intensity was evaluated by the percentage of specific ⁵¹Cr-release.