Figure 2.

IDO deficiency is associated with enhanced infiltration and accumulation of T cells in tumors after anti–CTLA-4 therapy. B16F10 tumors from untreated and anti–CTLA-4–treated WT and IDO^−/− mice were harvested 15 d after tumor challenge and analyzed by flow cytometry for their content of effector T cells and T reg cells. (A) Tumor weights. (B) Absolute numbers of CD45⁺, CD4⁺Foxp3⁻, and CD8⁺ cells per gram of tumor. (C) Percentage of CD4⁺Foxp3⁺ T cells of total CD45⁺ cells, and representative dot plots, for anti–CTLA-4-treated WT and IDO^−/− mice. (D) Ratio of CD4⁺Foxp3⁻ to CD4⁺Foxp3⁺ cells and CD8⁺ to CD4⁺Foxp3⁺ cells. (E) Percentage and representative dot plots of CD8⁺, CD4⁺Foxp3⁻ and CD4⁺Foxp3⁺ T cells expressing Ki67, PD-1 and ICOS, for untreated and treated IDO^−/− mice. Two-way ANOVA (A–B and D) and Student’s t test (C and E) were used to evaluate statistical significance (*, P < 0.05; **, P < 0.01; ***, P < 0.001; ****, P < 0.0001; NS, P < 0.1). Data shown are representative of two independent experiments with five independently analyzed mice/group.