IDO1 and neoplasm: Furthermore, we observed higher rates of intratumoral cytotoxic CD8+ T cells (P = 0.041, Mann–Whitney U test), a higher intratumoral CD8+ T cell/FoxP3+ Treg ratio (P = 0.012, unpaired t test), higher rates of CD8+Ki67+ T cells both in the stromal (P = 0.004, Mann–Whitney U test) and intratumoral (P < 0.001, Mann–Whitney U test) compartment, in tumors with IDO-positive tumor-infiltrating immune cells (Figures S1A–C in Supplementary Material).