PDCD1LG2 and neoplasm: Blocking humanized monoclonal antibodies against cytotoxic T lymphocyte antigen-4-mediated PD-1, PD-L1, and PD-L2 prevents binding to (CD80/CD86) allowing them to be available for CD28 binding and T-cell activation and decreasing immune tolerance to tumor associated antigens [38, 39] (Figure 2).