Anti-IgM– and IOR-T1-induced effects are not mediated by Fc receptor. B-CLL cells 2 × 10⁶/mL were incubated for 16 hours in RAM-Ig–coated 24-well plates with medium, anti-IgM, IOR-T1, mouse IgG2a, or mouse IgG1 MoAbs in combination as indicated. The percentage of apoptotic nuclei was determined using Hoechst staining.