Immune checkpoint is a kind of regulatory molecule in the immune system that is crucial for self-tolerance, which prevents the immune system from attacking cells indiscriminately. Immune checkpoint proteins play an important role in cancer immunotherapy research, and they function as co-stimulatory or co-inhibitory signals to enhance or inhibit immune responses. Targeting immune checkpoints by strengthening the immune response by agonists of co-stimulatory signals or antagonists of co-suppression signals is a novel strategy to attack tumor cells and treat cancers.
