By counteracting the pathological function of PD-1, antibodies that block PD-1 (e.g., Pembrolizumab and Nivolumab) and its ligand PD-L1 (e.g., Atezolizumab, Avelumab, and Duralumab) inhibit adaptive immune resistance and reinvigorate the immune response against cancer cells. Here, PDCD1 is linked to cancer.