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Image of CD4 co-receptor binding to MHC (Major Histocompatibility Complex) non-polymorphic region. In molecular biology, CD4 (cluster of differentiation 4) is a glycoprotein that serves as a co-receptor for the T-cell receptor (TCR). CD4 is found on the surface of immune cells such as helper T cells, monocytes, macrophages, and dendritic cells.
The T helper cells (T h cells), also known as CD4 + cells or CD4-positive cells, are a type of T cell that play an important role in the adaptive immune system. They aid the activity of other immune cells by releasing cytokines .
Type 1 immunity consists of these cells: [5] CD4+ T H 1 cells; CD8 + cytotoxic T cells (T c 1) T-Bet + interferon gamma producing group 1 ILCs(ILC1 and Natural killer cells) CD4 + T H 1 Cells. It has been found in both mice and humans that the signature cytokines for these cells are interferon gamma and lymphotoxin alpha.
This discovery furthered the development of a previously hypothesized theory, the immunosurveillance theory. The immunosurveillance theory suggests that the immune system routinely patrols the cells of the body, and, upon recognition of a cell, or group of cells, that has become cancerous, it will attempt to destroy them, thus preventing the growth of some tumors.
Boehme et al. demonstrated this interesting dual outcome by blocking the binding of CD4 to MHC-II which prevented the programmed cell death reaction that active T-cells typically display. [6] The CD4 receptor is composed of four concatamerized Ig-like domains and is anchored to the cell membrane by a single transmembrane domain.
CD40: This molecule, found on a variety of immune system cells including antigen presenting cells has CD40L, otherwise known as CD154 and transiently expressed on the surface of activated CD4+ T cells, as its ligand. CD40 signaling is known to ‘license’ dendritic cells to mature and thereby trigger T-cell activation and differentiation. [11]
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 + ).
CD4 cells develop into a diverse array of effector cell types depending on the nature of the signals they receive during priming. CD4 effector activity can include cytotoxicity , but more frequently it involves the secretion of a set of cytokines that directs the target cell to make a particular response.