PD-L1, an immune checkpoint molecule, is expressed by various cell types, including tumor cells, monocytes, macrophages, NK cells, DCs, and activated T cells.319 Monoclonal antibodies targeting immune checkpoints, such as anti-CTLA-4, anti-PD-1, and anti-PD-L1, have been used in immune checkpoint blockade therapy. The gene discussed is CTLA4; the disease is neoplasm.