Similar to the above results, Kyn markedly increased the percentage of PD-1+CD8+ T cells in TILs and inhibited the production of IFN-γ, while DMF showed a partial offsetting effect, which means that the excess production of Kyn may cause T cell exhaustion and impair the immune surveillance function of CD8+ T cells in the tumor microenvironment. The gene discussed is PDCD1; the disease is neoplasm.