C) immuntherapy and CAR-T-cell therapy
Immune Checkpoint inhibitors
■ In the immune system, different cells are involved. An important group is the so-called T-cells. They belong to the white blood cells and have the task of activating the downstream immune system or directly destroying intruders. T cells are controlled by means of recognition structures, so-called receptors, and activated with the help of such “checkpoints” as needed or “switched off” again in their function.
■ Manually control immune checkpoints: Two of these receptors are CTLA-4 (cytotoxic T-lymphocyte antigen 4) and PD-1 (programmed cell death). They mediate the suppression of the immune system (immunosuppression). If these proteins are deactivated, the T cells are activated and, above all, can cause the direct destruction of tumor cells.
■ However, tumors have the ability to also produce and send proteins that bind to PD-1. This stimulates its activity and paralyzes the function of the T cells. Antibodies directed against such processes are therefore called checkpoint inhibitors and cause the T cells to become activated. Brake blockade against cancer.
■ (A) T-killer cells are activated by recognition of a specific antigen. If the protein PD-1 (Programmed Death-1) on the T cell binds to the brake signal PD-1-L1 on the tumor cell, a T cell attack is blocked. Cancer continues to grow. (B) An antibody produced in the laboratory helps against the brake blockage.
■ When administered to the patient, the braking mechanism of PD-1 is blocked and the T cell can destroy the cancer cell. This procedure helps about one-fifth of the patients.