ZAP70 and B-cell chronic lymphocytic leukemia: Accordingly, 15/30 (50%) ZAP70+ CLL cells responded to the stimulation with up to four generations (median: 2 generations, with a significant (p = 0.0198) Pearson’s correlation coefficient between ZAP70 expression level and the number of cell generations), whereas only 8/28 ZAP70− CLL cells proliferate with a maximum of two generations.