Analysis of downstream signaling events in CLL cells treated with IL-4. CLL cells were incubated for 18 hours in the presence of 100μM Z-VAD-FMK. IL-4 (10 ng/mL) or PF-956980 (1μM) were added, as indicated. Protein lysates were analyzed by Western blotting using phosphorylation state-specific antibodies, as indicated. Isolates from CLL18 and 16 were used in the experiments depicted in panels A and B, respectively. The data are representative of 9 (A) and of 5 (B) independent experiments.