Zhx2 loss enhances NK response to IL-15 stimulation. (A) GSEA of Zhx2 mRNA expression and IL-15 signaling–related gene signatures. NES, normalized enrichment score. (B) FACS plots and graph show CD122 expression levels in gated CD3⁻NK1.1⁺ cells (representative of three independent experiments). MFI, mean fluorescence intensity. (C) FACS plots and graphs depict STAT5 (Tyr694) and AKT (Tyr308) phosphorylation in gated CD3⁻NK1.1⁺ cells after in vitro stimulation with IL-15 (representative of three independent experiments). (D) FCM analysis for CD107a and IFN-γ expression in splenic NK cells stimulated with the indicated concentrations of IL-15 (representative of two independent experiments). (E) Oxygen consumption rate (OCR) and maximum respiration of purified Zhx2^+/+ and Zhx2^Δ/Δ NK cells activated in vitro with IL-15 (representative of two independent experiments). Data shown were obtained under basal conditions and in response to the indicated molecules. FCCP, carbonyl cyanide 4-(trifluoromethoxy)phenylhydrazone. (F and G) Representative FACS plots and graph show the percentage of apoptotic cells (annexin V⁺7-AAD⁺) among Zhx2^+/+ and Zhx2^Δ/Δ NK cells. F shows that NK cells were cultured for 5 d with the presence of 5 ng/ml IL-15 (representative of two independent experiments). G shows that NK cells were stimulated with IL-15 in the presence of DMSO or STAT5-Inh (10 mM). FCM analysis of NK cell viability is shown (representative of two independent experiments). Dots represent data from individual mice, and error bars represent SEM per group in one experiment. Data were analyzed using Student’s t test (two-tailed paired t test). **, P < 0.01; ***, P < 0.001.