Blimp1 is dispensable for most effector functions of NK cells. (A-B) Gated TCRβ⁻NK1.1⁺CD49b⁺ NK cells from mixed bone-marrow chimeras, generated as described in Figure 3D, were examined for (A) granzyme B and (B) IFNγ expression by intracellular staining and flow cytometry. Numbers in the plots show the proportion of NK cells in each quadrant. Before analysis, the cells were stimulated with either (A-B) IL-12 and IL-18 or (B) PMA and ionomycin for 5 hours as indicated. Graph in (A) shows the mean fluorescence index (MFI) of granzyme B in Blimp1^+/+ and Blimp1^gfp/gfp NK cells. Data are the means ± SEM of 6 mice of each genotype. P value compares the indicated genotypes. (C-D) DX5⁺ NK cells from wild-type and Blimp1^gfp/gfp mice were expanded for 5 days in IL-15, transferred into conditions as indicated for another 2 days, and the quantity of secreted IFNγ and IL-10 (C) and cytotoxic activity against RMAS-Rae1β and RMAS-MSCV (D) was determined. Data in panels C-D are the means of triplicate measurements ± SEM and are representative of 3-5 experiments.