Increased IDO1 expression in the gut mucosa is associated with modulation of IL-17 and IFN-γ secretion by NKp44⁺ cells. (A) Monofunctional analyses of stimulated NKp44⁺ NK cells as shown in Figure 6A were correlated with relative expression values of IDO in whole biopsy specimens of the same animals. P values < .05 are considered significant. (B) Multiparametric analyses of NKp44⁺ NK cells function using SPICE 5.0 for individual naive and SIV-infected animals. Corresponding relative expression (RE) of IDO1 and plasma viral loads (VL) of infected animals are shown.