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The CD8 protein is a cell surface glycoprotein found on most cytotoxic T lymphocytes that mediates efficient cell-cell interactions within the immune system.The CD8, acting as a coreceptor, and the T-cell receptor on the T lymphocyte recognize antigen displayed by an antigen-presenting cell (APC) in the context of class I MHC molecules.
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 ...
The CD8 co-receptor is predominantly expressed on the surface of cytotoxic T cells, but can also be found on natural killer cells, cortical thymocytes, and dendritic cells. The CD8 molecule is a marker for cytotoxic T cell population. It is expressed in T cell lymphoblastic lymphoma and hypo-pigmented mycosis fungoides. [4]
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.
The majority of IELs (80%) are CD3+, and over 75% of these also express CD8.IELs can be divided into two major subsets based on their CD8 coreceptor expression. [5] One subset of IELs typically express activation marker CD8αα and some IELs express CD8αβ + marker (CD8αβ promotes TCR activation, whereas CD8αα suppresses TCR signals).
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 + ).
Some parts of this process may differ in CD4+ and CD8+ cells. For example, synapse formation is quick in CD8+ T cells, because for CD8+ T cells it is fundamental to eliminate the pathogen quickly. In CD4+ T cells, however, the whole process of the immunological synapse formation can take up to 6 hours. [13] [1]
Priming of naïve T cells requires dendritic cell antigen presentation. Priming of naive CD8 T cells generates cytotoxic T cells capable of directly killing pathogen-infected cells. CD4 cells develop into a diverse array of effector cell types depending on the nature of the signals they receive during priming.