tsütotoksiinit

Tsütotoksiinit, also known as cytotoxic T lymphocytes (CTLs) or T-killer cells, are a type of T lymphocyte that plays a crucial role in the adaptive immune system. Their primary function is to identify and eliminate cells that are infected with viruses, damaged, or cancerous. Tsütotoksiinit recognize specific antigens presented on the surface of target cells by MHC class I molecules. Once a tsütotoksiini recognizes a foreign or altered antigen, it initiates a cytotoxic response.

The mechanism of action for tsütotoksiinit involves the release of cytotoxic molecules. Two main pathways are employed. The first involves the release of perforin and granzymes. Perforin molecules create pores in the target cell membrane, allowing granzymes to enter the cell. Granzymes are proteases that trigger apoptosis, a programmed cell death pathway, in the target cell. The second pathway involves the Fas ligand (FasL) expressed on the tsütotoksiini surface binding to the Fas receptor (FasR) on the target cell. This interaction also initiates apoptosis in the target cell.

Tsütotoksiinit are essential for controlling viral infections and preventing the spread of pathogens within the body. They are also critical in tumor surveillance, recognizing and destroying precancerous or cancerous cells before they can proliferate and form tumors. The development and maturation of tsütotoksiinit occur in the thymus, where they undergo positive and negative selection to ensure they are self-tolerant and can effectively recognize foreign antigens. Their precise targeting and ability to induce cell death make them a vital component of cell-mediated immunity.