PDCD1 and neoplasm: Further, the CBM588-induced immunogenic conversion of the tumor-infiltrating lymph nodes is related to the Indoleamine 2,3-Dioxygenase 1/Inerleukine 10 (IDO1/IL-10) axis upon PD-1 blockade (IDO1 catalyzes the initial step in the degradation of tryptophan) [57].