PDCD1

PDCD1 encodes PD-1, the brake pedal that normally stops immune T-cells from attacking the body's own healthy tissue. When a T-cell binds a partner protein called PD-L1, PD-1 sends a stop signal that shuts the cell down, a safeguard against autoimmune disease. Tumors hijack this same brake by covering themselves in PD-L1, tricking exhausted T-cells into leaving cancer cells undisturbed instead of destroying them. Drugs that block PD-1, discovered through work that earned a Nobel Prize in 2018, release that brake and let the immune system recognize and kill tumors it had been ignoring. This approach, known as checkpoint inhibition, has become one of the most important advances in cancer treatment in decades. The same pathway also explains why PD-1 variants are studied in autoimmune conditions, where too little braking lets the immune system turn against the body.