IL-13–induced PB B-cell survival and expression of Bcl-2 family members. PB B cells were cultured in vitro for 48 hours with the indicated stimuli, and relative protein expression of Mcl-1, Bcl-xL, Bcl-2, Bak, and Bax was determined by Western blotting. Each lane was loaded with 10 μg of total protein, and as a control for equal loading the expression of the nuclear antigen p83 was used. For comparison, levels of Bcl-2 homologues in the B-cell line Karpas 422 are shown. The following concentrations were used: anti-μ (37.5 μg/mL), TPA (10 nmol/L), IL-4 (40 ng/mL), IL-13 (40 ng/mL), and rhuCD40L (10 ng/mL). In (A), one representative blot is shown, whereas the expression of Mcl-1 and Bcl-xL relative to expression in unstimulated cells determined by densitometry is shown in (B) and (C), respectively (mean ± SEM from 3 separate experiments).