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How do cytotoxic T cells destroy infected cells and cancer cells?
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immune system
Stimulation of immune response by activated helper T cells. Activated by complex interaction with molecules on the surface of a macrophage or some other antigen-presenting cell, a helper T cell proliferates into two general subtypes, TH1 and TH2. These in turn stimulate the complex pathways of the cell-mediated immune response and the humoral immune response, respectively.
Cytotoxic T cells (also known as killer T cells) play a critical role in cell-mediated immunity by identifying and destroying body cells that have been infected by viruses or transformed into cancer cells.
These cells function by using their T-cell receptors to bind to specific foreign antigens displayed on the surface of target cells in association with major histocompatibility complex (MHC) class I molecules. The bond is strengthened by the CD8 coreceptor.21
Once attached, cytotoxic T cells destroy the target cell through two primary mechanisms:
- Pore-forming molecules: Granular cytotoxic T cells release the contents of their cytotoxic granules, such as perforins, at the site of contact. This renders the target cell membrane permeable, causing the cell contents to leak out and leading to cell death.2
- Apoptosis: Nongranular cytotoxic T cells can induce apoptosis, or programmed cell death. This often occurs when a protein on the T cell interacts with the Fas protein on the target cell, sending a signal to the nucleus that initiates the cell's self-destruction.2