PDCD1 and cancer: After 2010, cancer immunotherapy research introduced new monoclonal antibodies targeting tumor antigens and T-cell protein receptors to downregulate the immune response, specifically the immune checkpoint inhibitor monoclonal antibodies anti-cytotoxic T-lymphocyte-associated antigen 4 (anti-CTLA4) and anti-programmed cell death protein 1 antibody (anti-PD1).