PDCD1 and neoplasm: PD-L2 is expressed mainly on dendritic cells, macrophages, mast cells, and certain B cells in response to IL-4 and IFN.358,359 In addition to those immune cells, PD-L1 is expressed on tumor cells and protects them from immune surveillance; a high level of PD-L1 on tumor cells is associated with poor prognosis in patients.360–363 Therefore, PD-1/PD-L1 pathway blockade can promote T-cell activation and cytokine production and preserve the antitumor capacity of T cells in the treatment of lymphomas.364