PD-L1 is a protein found on the surface of cells that plays a crucial role in regulating the immune system. It helps to prevent the immune system from attacking the body's own tissues by binding to a receptor called PD-1 on immune cells. This interaction can inhibit the immune response, allowing cancer cells to evade detection and destruction. In cancer research, PD-L1 has gained attention as a target for immunotherapy. Drugs that block PD-L1 or its receptor PD-1 can enhance the immune system's ability to recognize and fight cancer cells. This approach has shown promise in treating various types of cancer, including melanoma and lung cancer.