Fig. 4

Enhancement of NK cell activation by IDO ablation. a NK cell frequency and number. The frequency and absolute number of CD3⁻NK1.1⁺DX5⁺ NK cells in the spleen were determined by flow cytometric analysis 2 dpi. Values in representative dot plots on the left denote the average percentage of splenic NK cells derived from at least four mice per group, after gating on CD3⁻ cells; the bar graph on the right denotes the average ± SD of splenic NK cell numbers derived from at least four mice per group. b, c Activation of NK cells. The activation of CD3⁻NK1.1⁺DX5⁺ NK cells was evaluated by intracellular IFN-γ and granzyme B (GrB) staining upon stimulation with PMA plus ionomycin. Values in the representative dot plots on the left denote the average percentage of IFN-γ- or GrB-producing NK cells derived from at least four mice per group; the bar graphs on the right show the average number ± SD of NK cells producing IFN-γ or GrB in the spleens of at least four mice per group. **p < 0.01; ***p < 0.001 compared with levels in the indicated groups