Immune checkpoint inhibitors
When confronted with microbes, the immune system uses a system of ‘checkpoints’ to speed up or slow down its immune response. During an infection, the immune system accelerates its response in order to eliminate external agents, then slows down once elimination is complete.
Unlike a classic infection, cancer cells have the ability to slow down the immune system, thus avoiding elimination. Checkpoint inhibitor immunotherapy blocks this ability, thus reactivating the immune system so it will destroy the cancer cells.
Immune checkpoint inhibitors used today generally target the CTLA-4 protein, the PD-1 receptor, and the PDL-1 ligand.