PARP-14 mediates IL-4–induced B-cell rescue from apoptosis. (A,B) Role of PARP-14 in IL-4-induced B-cell protection against apoptosis. Splenocytes from WT, PARP-14 KO, and PARP-1 KO mice were cultured (20 hours) in the presence or absence of IL-4 and analyzed by TUNEL after death by neglect (A) or after irradiation (2 Gy) (B). FACS profiles show TUNEL data (avidin-FITC) from the B220⁺ gate in a representative experiment. Bar graphs show mean (± SEM) quantitation of the reductions in apoptosis for IL-4–treated samples of the indicated genotypes (n = 5 for WT, PARP-14–null; n = 3 for PARP-1^−/−; *P < .05) compared with the matched medium-only sample [“% decrease in death” = (% TUNEL⁺_medium-only minus% TUNEL⁺_{IL-4–treated})/% TUNEL⁺_medium-only]. Inset numbers indicate both the percentage of events TUNEL-positive in the samples and mean fluorescence intensity for the overall population. (C,D) Stat6 mediates IL-4 protection of B cells from radiation-induced death. WT and Stat6 KO B cells were analyzed for death by neglect (C) or after irradiation (D) as in panels A and B; samples are representative of the 5 independent experiments averaged to formulate the bar graphs of mean ( ± SEM) quantitative data. Results congruent with these data were also observed by annexin V staining (not shown).