Kinetics of F-ara-Ainduced (A) and spontaneous (B) apoptosis in T-normal and B-CLL peripheral lymphocytes from 25 patients. Suspensions of peripheral lymphocytes were incubated alone or in the presence of 3 μmol/L F-ara-A for 72 hours. Patients were grouped according to Rai stages 0 to I (solid bars) and stages II to IV (open bars). Apoptosis was measured by using ISEL in antigen-defined lymphocyte subpopulations and expressed as percentages. Bars represent the mean values in each group plus standard deviation. Statistical significance was evaluated at 72 hours, using the Studentt-test.