Imatinib inhibits CD154-induced sensitization of CLL cells to CD95-mediated apoptosis. CLL cells were cultured for 24 hours on CD154-bearing adherent cells in media containing 0 μM (medium), 1 μM, 3 μM, or 10 μM imatinib, as indicated at the bottom of the graph. On day 5, the CLL cells were isolated and then cultured with CHO (▴) or CHO-CD178 (▪) effector cells. The percentage of CLL cells undergoing apoptosis after 24 hours is indicated on the y axis (% apoptosis). This graph provides a representative assay performed twice on the CLL cells of one patient. Each data point is the mean plus or minus the standard error of the 2 assays.