cluster of differentiation

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clus·ter of dif·fer·en·ti·a·tion

(klŭs'ter dif'er-en'shē-ā'shŭn),
Cell membrane molecules that are used to classify leukocytes into subsets. CD molecules are defined or classified by the reference monoclonal antibodies to which they bind. There are many clusters of differentiation; many cells express more than one CD marker. A phenotypic characterization of a cell of hematopoietic origin may be made by examining the pattern of CD markers expressed at any given time. The physiologic function has been identified for many, but not all, known CDs. There are four general types: type I transmembrane proteins have their COOH-termini in the cytoplasm and their NH2-termini outside the cell; type II transmembrane proteins have their NH2-termini in the cytoplasm and their COOH-termini outside the cell; type III transmembrane proteins cross the plasma membrane more than once and hence may form transmembrane channels; and glycosylphosphatidylinositol-anchored proteins (type IV), which are tethered to the lipid bilayer through a glycosylphosphatidylinositol anchor.

clus·ter of dif·fer·en·ti·a·tion

(CD) (klŭs'tĕr dif'ĕr-en-shē-ā'shŭn)
Cell membrane molecules that are used to classify leukocytes into subsets. CD molecules are classified by monoclonal antibodies. There are four general types: type I transmembrane proteins have their COOH-termini in the cytoplasm and their NH2-termini outside the cell; type II transmembrane proteins have their NH2-termini in the cytoplasm and their COOH-termini outside the cell; type III transmembrane proteins cross the plasma membrane more than once and hence may form transmembrane channels; and glycosylphosphatidylinositol-anchored proteins (type IV), which are tethered to the lipid bilayer through a glycosylphosphatidylinositol anchor.

cluster of differentiation

Abbreviation: CD
Any of a group of cell surface protein markers on the white blood cells. These markers are used to classify immune cell types and establish international nomenclature standards. The markers are found on many blood cells and some nonblood cells but are used most often to refer to lymphocytes. The markers may be identified by specific monoclonal antibodies and are used to designate cell populations, e.g., CD4 lymphocytes as T helper cells, and CD8 lymphocytes as suppressor T cells. Each marker has a specific function in the cell, such as passing a signal from the T-cell receptor to the cytoplasm. Particular CDs are followed by numbers (CD2, CD3, etc.) and are so listed. See: e.g., CD2; CD7; CD68
See: T cell
See also: cluster

clus·ter of dif·fer·en·ti·a·tion

(CD) (klŭs'tĕr dif'ĕr-en-shē-ā'shŭn)
Cell membrane molecules that are used to classify leukocytes into subsets. CD molecules are classified by monoclonal antibodies.