PDCD1 and neoplasm: Furthermore, in a melanoma model, the “exhausted” (showing reduced cytokine production capability) tumor-reactive CD8+ T cells, compared with “non-exhausted” bystander CD8+ T cells, had Pdcd1 upregulation but downregulation of genes involved in CD8+ T cell survival and function (Il7r, Bcl2, Cxcr3, Ifngr1, and Ifngr2) (14).