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Antigen presentation stimulates T cells to become either "cytotoxic" CD8+ cells or "helper" CD4+ cells.. A cytotoxic T cell (also known as T C, cytotoxic T lymphocyte, CTL, T-killer cell, cytolytic T cell, CD8 + T-cell or killer T cell) is a T lymphocyte (a type of white blood cell) that kills cancer cells, cells that are infected by intracellular pathogens such as viruses or bacteria, or ...
After a precursor cell has been activated, it can then differentiate into a functional CTL with cytotoxic activity. There are three sequential signals that are required to complete this process. First, there is TCR recognition of the peptide-MHC class I complex. This step allows the cell to become licensed to an antigen-presenting cell.
The process of formation begins when the T-cell receptor binds to the peptide:MHC complex on the antigen-presenting cell and initiates signaling activation through formation of microclusters/lipid rafts. Specific signaling pathways lead to polarization of the T-cell by orienting its centrosome toward the site of the immunological synapse. The ...
After vaccine induced activation, dendritic cells are able to migrate to lymph nodes and activate CD4+ T helper cells as well as cross prime CD8+ T cytotoxic cells. This mass generation of activated tumor specific CD8+ T cells increases anti-tumor immunity, and is also able to overcome many of the immune suppressive effects of tumor cells. [10]
Markers of T cell activation include CD69, CD71 and CD25 (also a marker for Treg cells), and HLA-DR (a marker of human T cell activation). CTLA-4 expression is also up-regulated on activated T cells, which in turn outcompetes CD28 for binding to the B7 proteins. This is a checkpoint mechanism to prevent over activation of the T cell.
Only licensed dendritic cells are able to activate cytotoxic T cells. T cell licensing of dendritic cells is key for activation of cytotoxic T cells for many pathogens, although the extent to which T cell help is needed may vary. [14] In MHC class I and class II molecules, only certain epitopes of an internalized peptide can be presented.
Cytotoxic T cells regularly patrol all body cells to maintain the organismal homeostasis. Whenever they encounter signs of disease, caused for example by the presence of viruses or intracellular bacteria or a transformed tumor cell, they initiate processes to destroy the potentially harmful cell. [1] All nucleated cells in the body (along with ...
CD8 + cytotoxic T-cells may also be categorized as: [5] T c 1 cells, T c 2 cells. Similarly to CD4 + T H cells, a third category called T C 17 were discovered that also secrete IL-17. As for the ILCs, they [Clarification needed.] may be classified into three main categories [5] ILC1 which secrete type 1 cytokines, ILC2 which secrete type 2 ...