T-bet–dependent Blimp1 expression in NK cells. Flow cytometric analysis of gated splenic TCRβ⁻NK1.1⁺CD49b⁺ NK cells from mixed bone-marrow chimeric mice that were generated as described in Figure 3D. (A) Splenic NK cells from mixed bone-marrow chimeric mice of the genotypes indicated were examined for T-bet and Eomes levels by intracellular staining and flow cytometry. Shown is the expression in TCRβ⁻NK1.1⁺CD49b⁺ NK cells of the indicated genotype (Blimp1^gfp/gfp [Ly5.2⁺], filled gray histograms) and wild-type (Ly5.1⁺, empty histograms). Tbx21^−/− NK cells are shown as a control for the T-bet staining; naive CD4⁺ T cells are shown as a control for the Eomes stain (dashed lines). (B) Blimp1/GFP expression in Tbx21^−/−Blimp1^gfp/+ (filled gray histogram) and control (empty histogram, wild-type; filled black histogram, Blimp1^gfp/+) NK cells. (C-D) Gated splenic TCRβ⁻NK1.1⁺CD49b⁺ NK cells from mixed bone-marrow chimeric mice were analyzed by flow cytometry for the indicated markers. Data in panel C show analysis of Ly5.2⁺ NK cells of the indicated genotypes. Data in panel D show total NK cells. Numbers in the plots show the proportion of NK cells in each quadrant. The results are representative of 2 experiments each with 3 mice.