Mechanism of action of immunotherapy.

The immune system plays a vital role in regulating the growth of tumors. Some types of inflammatory responses can promote tumor growth, while a tumor-specific adaptive immune response can potentially control tumor growth. Malignancies have the ability to evade the immune system, and proliferate and metastasize. The goal of immunotherapy is to marshal the specificity and long-term memory of the adaptive immune response to achieve durable tumor regression and possible cure, although, to date, this has been achieved in only a small subset of patients. A variety of approaches to immunotherapy have been investigated. These include administration of exogenous cytokines or therapeutic vaccines to increase the frequency of tumor-specific T cells, adoptive transfer of tumor-specific immune effector cells, and, more recently, the application of a variety of immune checkpoint inhibitors and agonists of co-stimulatory receptors to overcome tumor-induced immune-suppressive mechanisms. Some approaches have been more successful than others for reasons that are now becoming apparent, and these observations have led to an exciting resurgence in clinical research to develop more effective immunotherapeutic strategies.