PD-1

PD-1 (programmed cell death protein 1) is a molecule found on immune cells called T-cells. Its role is to help regulate the immune response by acting as a checkpoint, preventing T-cells from overreacting and attacking the body’s own tissues. When PD-1 binds to its partners (PD-L1 or PD-L2), it reduces T-cell activity. Some cancer cells use this pathway to avoid immune attack by producing PD-L1. Therapies called checkpoint inhibitors block PD-1 or PD-L1, reactivating T-cells to better recognize and destroy cancer cells.