Induction of apoptosis. Cells were cultured for 24 hours in the presence of 22-20, 20-22, v-mab, e-mab, or a combination of v-mab and e-mab at 50 nM. (A) Apoptosis was measured by Guava Nexin for Daudi and Raji. The percentage of early apoptotic cells (annexin V–PE⁺/7-AAD⁻) is shown. (B) Apoptosis was measured by Guava MultiCaspase for Ramos and Raji after staining with SR-VAD-FMK. (C) The effect of caspase inhibitor (CI) on apoptosis of Ramos induced by 22-20, 20-22, or anti-IgM (5 μg/mL, a positive control for caspase-dependent apoptosis). Cells were cultured for 24 hours in the presence the indicated reagent alone or in the presence of Z-VAD-FMK at 20, 50, or 100 μM, and then analyzed by Guava Nexin.