Home > Cluster of differentiation
Cluster of Differentiation (CD) molecules are markers on the cell surface, as recognized by specific sets of antibodies, used to identify the cell type, stage of differentiation and activity state of a cell. The CD nomenclature was proposed and established in the 1st International Workshop and Conference on Human Leukocyte Differentiation Antigens (HLDA), which was held in Paris, France in 1982. This system was intended for the classification of the many monoclonal antibodies, generated by different laboratories around the world, against various surface molecules ( antigens) on leukocytes (white blood cells). Since then, the use has expanded to other cell types, and more than 150 CD clusters and subclusters have been identified.
CD molecules are not merely markers on the cell surface. Not every CD molecule has been thoroughly characterised, but most of them bring important features to the cells that carry them. For example,
- CD31 = PECAM-1, a cell adhesion molecule on platelets and endothelial cells
- CD35 = Complement receptor 1 (C3b/C4b receptor)
- CD36 = Platelet glycoprotein IV or IIIb (GP IV / GP IIIb)
- CD71 = Transferrin receptor, mediates cellular uptake of iron
- CD117 = c-kit, the receptor for Stem Cell Factor, a glycoprotein that regulates cellular differentiation, particularly in hematopoiesis
- CD120 = a receptor for Tumour Necrosis FactorIn medicine, tumor necrosis factor alpha (TNF, cachexin or cachectin) is an important cytokine involved in systemic inflammation and the acute phase response. Structure TNF is a member of a group of other cytokines that all stimulate the acute phase react, an inflammatory cytokineCytokines are small protein molecules that are the core of communication between immune system cells, and even between immune system cells and cells belonging to other tissue types. They are actively secreted by immune cells. Their action is often local,
- CD142 = Tissue Factor, a major initiator of blood-clottingCoagulation is the thickening or congealing of any liquid into solid clots. This article is about a specific medical usage of the term with reference to human blood's mechanisms for forming scabs over wounds. The coagulation of human blood is a fairly com
- CD143 = Angiotensin-converting enzymeAngiotensin-Converting Enzyme ACE EC ) is a exo peptidase that catalyses the conversion of Angiotensin I to Angiotensin II, a potent vasoconstrictor. ACE is also involved in the inactivation bradykinin, a potent vasodilator. This explains the alternate na
- CD144 = VE-Cadherin, a calcium-dependent adhesion molecule at intercellular junctions, found only in the vascular endothelium
- CD202a = Tie2, the receptor for Angiopoietins, a family of angiogenicAngiogenesis is the physiological process involving the formation of new blood vessels from pre-existing vessels. This is a normal process in growth and development, as well as in wound healing. However, this is also a fundamental step in the transition o factors
CD molecules are often referred to when sorting cells by flow cytometryFlow cytometry is a technique for counting, examining and sorting microscopic particles suspended in a stream of fluid. It allows perform a mutiparametrical simultaneous analysis of the physical or/and chemical chracteristics of single cells flowing throu. A '+' or a '–' symbol is used to indicate if a certain fraction of cells possesses or lacks a CD molecule, e.g. "CD34+, CD31–" = expressing CD34, but not CD31.
The most commonly referred to CD molecules are CD4 and CD8, which are markers for two different sub-types of T-lymphocytesT cells are a subset of lymphocytes that play a large role in the primary immune response. The abbreviation "T" stands for thymus, the organ in which their final stage of their development occurs. There are many types of T cells: Cytotoxic T cells (CD8+). The relative abundance of CD4+ and CD8+ cells reflects the state of one's immune system, and the CD4/CD8 ratio is often used to monitor the progression of an HIV infection.
External links
