In the immune system, the PD-1/PD-L1 pathway acts as a checkpoint to prevent overactivation and autoimmune reactions. However, many cancers exploit this pathway by expressing PD-L1, which binds to PD-1 on T-cells, effectively "turning off" these immune cells. PD-L1 inhibitors bind to PD-L1, preventing this interaction and allowing T-cells to remain active against cancer cells.
