IL-13 inhibits cell death of normal PB B cells in vitro. (A) PB B cells were cultured in medium or in the presence or absence of rhu IL-4 or rhu IL-13, both at 40 ng/mL. Viability was measured at the indicated time points by PI-exclusion using flow cytometry. Results (mean ± standard error of mean [SEM]) are from five experiments. (B) Cells were cultured for 3 days with IL-13 or IL-4 at the indicated concentrations, and the proportion of dead cells was measured by PI staining (vital dye exclusion). Results are presented as means ± SEM (n = 8). * Significantly different from control values according to the paired Wilcoxon test (P < .05).