CD127⁺ NK cells preferentially induce CD25 expression in response to IL-12. (A–C) Cell surface expression of CD127 and CD25 on NK cells from mock treated, day 10 DT treatment (DTX) Foxp3^DTR mice, or 3-wk-old Foxp3^−/− mice (A) and tumor-bearing mice on day 16 of s.c. B16 melanoma implantation (B) or on day 21 of chronic viral infection with LCMV clone 13 (C). (D) CD25 expression of NK cells stimulated for 18 h in vitro with the indicated concentrations of IL-12 and PBS control, IL-10, or TGF-β. (E and F) Expression of CD25 (E) and IL12Rβ1 (F) on splenic NK cells from mice that received (i.v.) the indicated doses of IL-12 16 h before analysis. Numbers in histograms show background-subtracted mean fluorescence intensity. FMO, full minus one control. The data are representative of two to three independent experiments.