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CD8+(cytotoxic) T cells

CD8+(cytotoxic) T cells

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🔱CD8+ (cytotoxic) T cells, like CD4+ Helper T cells, are generated in the thymus and express the T-cell receptor.
🔱 CD8, usually composed of one CD8α and one CD8β chain. 🔱CD8+ T cells recognise peptides presented by MHC Class I molecules, found on all nucleated cells.

🔱CD8+ T cells (often called cytotoxic T lymphocytes, or CTLs) are very important for immune defence against intracellular pathogens, including viruses and bacteria, and for tumour surveillance.

🔱 When a CD8+ T cell recognises its antigen and becomes activated, it has three major mechanisms to kill infected or malignant cells. The first is secretion of cytokines, primarily TNF-α and IFN-γ, which have anti-tumour and anti-viral microbial effects.

🔱The second major function is the production and release of cytotoxic granules. These granules, also found in NK cells, contain two families of proteins, perforin,and granzymes. Perforin forms a pore in the membrane of the target cell, similar to the membrane attack complex of complement.
This pore allows the granzymes also contained in the cytotoxic granules to enter the infected or malignant cell.
Granzymes are serine proteases which cleave the proteins inside the cell, shutting down the production of viral proteins and ultimately resulting
in apoptosis of the target cell.

🔱The third major function of CD8+ T cell destruction of infected cells is via Fas/FasL interactions( Apoptosis).
🔱In addition to their critical role in immune defense against viruses, intracellular bacteria, and tumours, CD8+ T cells can also contribute to an excessive immune response that leads to immunopathology, or immune-mediated damage.

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