Bcl-x_L promotes survival of eosinophils with constitutively active NF-κB. (A) RNA was isolated from sort-purified eosinophils of EpxCre/R-RFP/IκB^F/+ (gray bars) and EpxCre/R-RFP/IκB^F/F (black bars) mice. Expression of bcl-2 and bcl-x_L was determined by RT-qPCR. Porphobilinogen deaminase was used as housekeeping control. Bar graphs show the mean + SEM of 4 mice per group. *P < .05. (B) Eosinophils (Siglec-F⁺SSC^hi) from spleen and peritoneum of IL-5 transgenic mice were stained intracellularly for expression of Bcl-2 and Bcl-x_L (black outline) and compared to isotype control staining (gray shade). (C) RT-qPCR for bcl-x_L in BMDEs stimulated for 3 hours with IL-5 (left graph) or GM-CSF (right graph) in the presence or absence of the NF-κB inhibitor (inh.) Bay11-7085. Bar graphs show the mean + SEM of 6 separate samples per group from 2 independent experiments. *P < .05; **P < .01; ***P < .001. (D) BMDEs from wild-type mice were retrovirally transduced with either mock or bcl-x_L–expressing retroviruses. Dot plots show frequencies of transduced eosinophils (reporter⁺Siglec-F⁺) before (day 0) and after (day 4) IL-5 withdrawal. Similar results were obtained in 2 other independent experiments. 2^−ΔCt, the difference of Ct values obtained by RT-PCR analysis between the gene of interest and the house-keeping gene; GFP, green fluorescent protein; qPCR, quantitative PCR.