Induction of apoptosis by BL22 in the presence of IL-4. B-CLL cells were grown for 72 hours in the presence or absence of 10 ng/mL IL-4 and 1000 ng/mL BL22. Cells were then stained with PI and Annexin V-FITC, as described in “Patients, materials, and methods.” Numbers indicate the percentages of viable cells (Annexin V^-/PI^-).