In vitro, exposure to kynurenine inhibits IFN-γ and TNF-α production in CD8+ T cells; in vivo, IDO knockdown in colon carcinoma cell lines before engraftment reduces the expression of the ICs: PD-1, CTLA-4, and LAG3 in CD8+ TILs. The gene discussed is CD8A; the disease is colon carcinoma.