programmed cell death 1 (PD-1)

Programmed Cell Death Protein 1 (PD-1) is a receptor found on immune cells, specifically T cells, which play a key role in fighting infections and cancer. When PD-1 binds to its ligands (PD-L1 or PD-L2), it signals the T cell to reduce its activity, preventing excessive immune responses and protecting healthy tissues from damage. However, many cancer cells exploit this pathway by producing PD-L1 to turn off immune attacks, allowing tumors to grow unchecked. Drugs called PD-1 inhibitors can block this interaction, reactivating the immune system to better recognize and destroy cancer cells.