Comparison between the induction of apoptosis in B cells and T cells from 11 B-CLL patients. Cells were incubated with fludarabine (F) and/or mafosfamide (Mf) for 24 hours and phosphatidylserine exposure was measured by binding of annexin V-FITC to CD19⁺ or CD3⁺ cells as described in Materials and Methods. Statistical significance was determined using the t-test for nonpaired samples: *versus control; §versus fludarabine.