Detection of caspase-8 and caspase-3 activation and of Bcl-2 levels in IL-21-treated or untreated CD40-activated CLL B cells. (A) Caspase activation was detected by staining CLL B cells with cell-permeable fluorescent inhibitors of all caspases (PAN-CASP INH) or specific for caspase-8, caspase-3, and caspase-9. The bold line represents IL-21-treated cells, while the thin line represents untreated cells. (B) Permeabilized CLL B cells were analyzed for activated caspase-3 expression by the use of a fluorescent mAb specific for the active form of caspase-3. (C) Intracellular expression of Bcl-2, evaluated by the use of a Bcl-2-specific FITC-conjugated mAb, did not show significant modulation in IL-21-treated cells. Horizontal bar M1 is the marker of positive signal.