rhApo2L/TRAIL induces apoptosis and caspase-3/7 activation in NHL cells. BJAB (A), DoHH-2 (B), Ramos RA1 (C), and SC-1 (D) NHL cells were analyzed for cell viability by AlamarBlue staining after 48 hours of treatment with rhApo2L/TRAIL alone (•) or rhApo2L/TRAIL and rituximab (20 μg/mL, ■). Caspase-3/7 activity in Ramos RA1 cells was measured using a fluorescence assay after 24 hours of treatment under the conditions described for panels A-D. (E) Flow cytometric analyses of active caspase-3–positive Ramos RA1 cells as detected by a FITC-conjugated monoclonal antibody to active caspase-3 after 24 hours of treatment as described for panels A-D. (F) In every experiment, rhApo2L/TRAIL and rituximab were added simultaneously.