Loss of Pak2 activates STAT5 and downregulates IRF8 expression in MDSCs. (A) STAT5a gene expression and (B) STAT5 protein phosphorylation in Pak2-KO MDSCs or WT PMNs (progenies from the GM-CSF colony assays shown in Figure 3B) were determined by quantitative real-time PCR and flow cytometry, respectively. (C-D) IRF8 gene expression in Pak2-KO MDSCs or WT PMNs (progenies from the GM-CSF colony assays shown in Figure 3B) (C) and Pak2-KO or WT Gr1^highLy6G⁺ cells (MDSCs and PMNs, respectively) (D) isolated from spleen are shown. Representative data from 2 or 3 experiments with 3 to 6 mice per genotype are shown. *P < .05; ****P < .0001.