Pak2 disruption results in decreased spontaneous and Fas-FasL–induced apoptosis in MDSCs. (A) Freshly isolated splenocytes from mice reconstituted with Pak2-KO or WT BM were cultured in the presence or absence of FasL for 2 hours prior to CD11b, Gr1, Annexin V, and propidium iodide (PI) staining. The percentage of Annexin V⁺PI⁺ cells in the gated CD45.2⁺CD11b^highGr1^high population is shown. (B) Freshly isolated splenocytes from mice reconstituted with Pak2-KO or WT BM were stained for CD45.2, Fas, CD11b, Gr1, CD3, and B220. The MFI of Fas in gated CD45.2⁺ populations is shown. (C) Bcl2, (D) Mcl1, (E) Bcl-xL, (F) Bak1, and (G) Bax expression in Pak2-KO MDSCs or WT PMNs (progenies from the GM-CSF colony assays shown in Figure 3B) was determined by quantitative real-time PCR. Representative data from 3 or 4 experiments with 3 to 10 mice per genotype are shown. *P < .05; **P < .01; ***P < .001; ****P < .0001.