Anti-CD6 can prevent B-CLL cells from anti-IgM–induced DNA fragmentation. B-CLL cells from patient L-204 were incubated in RAM-Ig–coated 24-well plates with medium, anti-IgM, and/or IOR-T1. DNA fragmentation was determined after 16 hours using PI staining and FACS analysis. The percentage of apoptotic nuclei corresponding to M1 marker is in the left corner of each panel.