Induction of apoptosis by lumiliximab in CLL cells from patients with CLL and the transformed B-cell lines SKW6.4 and SB. (A) Freshly prepared CLL cells from 16 patients with CLL were incubated in the presence of 10 μg/mL lumiliximab or isotype control antibody. Apoptosis was measured using a flow cytometry-based assay for activated caspase-3 (*P value in t test, < .001). Data from a representative patient are shown in panels B and C. (B) Flow cytometric analysis of activated caspase-3 (open histogram, lumiliximab-treated; shaded histogram, isotype control). (C) Annexin V/propidium iodide staining: (i) an isotype control-stained sample and (ii) a lumiliximab-stained sample. (D) Induction of apoptosis by lumiliximab is crosslinking dependent. SKW6.4 cells (0.5 × 10⁶ cells/mL) were incubated with 10 μg/mL lumiliximab, with or without F(ab′)2 goat anti–human IgG for 18 hours. (E) Induction of apoptosis by lumiliximab is dose dependent. Incubation with lumiliximab was at the indicated concentrations, and F(ab′)2 goat antihuman IgG was included in all samples for 18 hours. Percentage apoptosis was determined as described in “Apoptosis assays.”