[Role of T cells in tumor immunology and immunotherapy]

In the immune defense against cancer, cell-mediated adaptive immune response is considered of primary importance, in which T lymphocytes play a key role. Activation, expansion and function of antigen-specific T cells is a multistep process and its outcome depends on the balance of positive and negative regulatory mechanisms controlling each step. Many factors can hamper the development of an efficient antitumor immune response, such as insufficient expression of tumor antigens or of molecules necessary for their processing, inhibitory molecular interactions (e.g. immune checkpoints), immune suppressive factors or suppressor cells. Various therapeutic strategies have been developed in order to increase the efficiency of antitumor immune defense, of which the application of immune checkpoint inhibitors, antibodies blocking the brakes of immune response, is the most widespread. These immunomodulatory antibodies had more favorable effect than traditional treatment modalities on a widening spectrum of tumor types, still the majority of patients do not or only transiently respond. Therefore, great efforts are made to develop rational combinations of immune and other therapies, and to identify resistance mechanisms and biomarkers predicting therapy outcome.