One of the possible reasons for treatment failure with PD-1 blockade is the presence of immune suppression through immune checkpoints other than the PD-1/programmed cell death ligand-1 (PD-L1) axis regulating lymphocyte activation and expansion or through immune suppressive cells including forkhead box P3 (Foxp3)+ CD25+ regulatory T cells (Tregs), T helper 2 (Th2) cells, myeloid-derived suppressor cells (MDSCs), tumor-associated macrophages, and plasmacytoid dendritic cells (pDCs) [8–13]. Here, PDCD1 is linked to neoplasm.