PDCD1 and neoplasm: While on one hand, TIL-derived IFN-γ upregulates exosomal PD-L1, thus protecting tumor cells from the surveillance of the immune system; on the other hand, CD8+ T cells inhibit the proliferation of tumor cells by secreting IFN-γ and exosomal PD-L1 may reduce the level of CD8+ T cells-derived IFN-γ through PD-L1/PD-1 interaction.