Influence of concentration and time of incubation on cell killing. CLL lymphocytes were treated with increasing concentrations of fludarabine (2.5, 5, 10 μM), oxaliplatin (2.5, 5, 10 μM), or the combinations (fludarabine 2.5 μM + oxaliplatin 2.5, 5, and 10 μM; fludarabine 5 μM + oxaliplatin 5 and 10 μM; fludarabine 10 μM + oxaliplatin 2.5, 5, and 10 μM) for 16 hours (A) or 36 hours (B). The range of concentrations is represented by a wedge. Annexin V–positive cells were considered apoptotic, presented as apoptotic cells (percentage of control). Each point is the mean ± SE of determinations on cell samples from 3 to 6 persons.