Zielzellenzytotoxizität

Zielzellenzytotoxizität describes the killing of target cells by cytotoxic cells. This process is a critical component of the immune system, particularly in adaptive immunity. Cytotoxic T lymphocytes (CTLs) and natural killer (NK) cells are the primary effector cells responsible for inducing target cell death. These cells recognize and bind to target cells, often through specific antigen-MHC interactions or receptor-ligand binding.

Upon recognition, cytotoxic cells release a variety of molecules that induce apoptosis or necrosis in the target cell. Two major mechanisms are involved. The first is the granule exocytosis pathway, where cytotoxic granules containing perforin and granzymes are released. Perforin forms pores in the target cell membrane, allowing granzymes to enter and activate caspases, leading to programmed cell death. The second pathway involves the Fas ligand (FasL) expressed on the cytotoxic cell interacting with the Fas receptor (FasR) on the target cell. This interaction also triggers caspase activation and apoptosis.

Zielzellenzytotoxizität plays a vital role in eliminating virus-infected cells, tumor cells, and foreign cells, such as those in organ transplants. Dysregulation of this process can lead to impaired immune responses, contributing to susceptibility to infections or cancer, or to autoimmune diseases and transplant rejection. Understanding these mechanisms is crucial for developing immunotherapies.