IL-13 inhibits DNA fragmentation in PB B cells. PB B cells were cultured for 3 days in medium, or in the presence or absence of IL-4 or IL-13. Cell death was measured by PI staining and the TUNEL assay. In (A) the results of one representative experiment are shown to indicate how cell death was estimated using the two methods. (B) shows the results (mean ± SEM) of eight (PI staining) and six (TUNEL staining) experiments. *Significantly different from the medium control values according to the paired Wilcoxon test (P < .05).