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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 ...
Once the Fc receptor binds to the Fc region of the antibody, the NK cell releases cytotoxic factors that cause the death of the target cell. During replication of a virus, some of the viral proteins are expressed on the cell surface membrane of the infected cell. Antibodies can then bind to these viral proteins.
Other cellular hypersensitivities include cytotoxic T cell mediated auto-immune disease, and a similar phenomenon; transplant rejection. Helper T cells are required to fuel the development of these diseases. In order to create sufficient auto-reactive killer T cells, interleukin-2 must be produced, and this is supplied by CD4 + T cells.
These cells are defined by the expression of the CD8 protein on their cell surface. Cytotoxic T cells recognize their targets by binding to short peptides (8-11 amino acids in length) associated with MHC class I molecules, present on the surface of all nucleated cells. Cytotoxic T cells also produce the key cytokines IL-2 and IFNγ.
T H 1 cells which produce interferon gamma and lymphotoxin alpha, T H 2 cells which produce IL-4, IL-5, and IL-13. A third category called T helper 17 cells (T H 17) were also discovered which are named after their secretion of Interleukin 17. CD8 + cytotoxic T-cells may also be categorized as: [5] T c 1 cells, T c 2 cells.
Cytokine signals produced by helper T cells enhance the microbicidal function of macrophages and the activity of killer T cells. [70] In addition, helper T cell activation causes an upregulation of molecules expressed on the T cell's surface, such as CD40 ligand (also called CD154), which provide extra stimulatory signals typically required to ...
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.
Natural killer cells, also known as NK cells, are a type of cytotoxic lymphocyte critical to the innate immune system.They are a kind of large granular lymphocytes [1] [2] (LGL), and belong to the rapidly expanding family of known innate lymphoid cells (ILC) and represent 5–20% of all circulating lymphocytes in humans. [3]