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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.
This activation of naive T cell is controlled by a variety of signals: recognition of antigen in the form of a peptide: MHC complex on the surface of a specialized antigen-presenting cell delivers signal 1; interaction of co-stimulatory molecules on antigen-presenting cells with receptors on T cells delivers signal 2 (one notable example ...
Activation of T cells without co-stimulation may lead to the unresponsiveness of the T cell (also called anergy), apoptosis or the acquisition of the immune tolerance. [ 3 ] The counterpart of the co-stimulatory signal is a (co-)inhibitory signal, where inhibitory molecules interact with different signaling pathways in order to arrest T cell ...
Cellular immunity protects the body through: T-cell mediated immunity or T-cell immunity: activating antigen-specific cytotoxic T cells that are able to induce apoptosis in body cells displaying epitopes of foreign antigen on their surface, such as virus-infected cells, cells with intracellular bacteria, and cancer cells displaying tumor antigens;
Compared to a normal antigen-induced T-cell response where 0.0001–0.001% of the body's T-cells are activated, these SAgs are capable of activating up to 20% of the body's T-cells. [3] Furthermore, Anti- CD3 and Anti- CD28 antibodies ( CD28-SuperMAB ) have also shown to be highly potent superantigens (and can activate up to 100% of T cells).
In immunology, a naive T cell (T h 0 cell) is a T cell that has differentiated in the thymus, and successfully undergone the positive and negative processes of central selection in the thymus. Among these are the naive forms of helper T cells ( CD4 + ) and cytotoxic T cells ( CD8 + ).
The TCR/peptide-MHC complex, formed when a T cell recognises its ligand on an antigen presenting cell (APC) and the T-cell-APC contact occurs, spans a short length. This results in the formation of close contact zones between the membranes of the T cell and antigen presenting cell (~15 nm apart) around the TCR/peptide-MHC complex. [3]
ITAMs are important for signal transduction, mainly in immune cells. They are found in the cytoplasmic tails of non-catalytic tyrosine-phosphorylated receptors [7] such as the CD3 and ζ-chains of the T cell receptor complex, the CD79-alpha and -beta chains of the B cell receptor complex, and certain Fc receptors.