PDCD1 and hematologic disorder: The clinical effectiveness of agents inhibiting CTLA-4 (cytotoxic T lymphocyte-associated protein 4, CD152) and PD-1/PD-L1 checkpoints (programmed cell death protein 1, CD279; programmed death-ligand 1, CD274) has led to swift regulatory approval for treating patients with various solid tumors and hematologic malignancies [109].