PDCD1 and neoplasm: Previously, the molecular basis of PD-1/PD-L1 blockade and tumor immunotherapy has been thoroughly reviewed (Chen and Han, 2015; Li et al., 2016; Zou et al., 2016), we briefly overviewed the current understanding of the molecular mechanisms of the PD-1/PD-L1 interaction and focused on the recently defined structural basis of the therapeutic antibody-based PD-1/PD-L1 blockade in the present review.