Cluster of Differentiation (CD) Proteins Background
Cluster of Differentiation (CD) is group of cell membrane molecules which are used to identify and classify leukocytes into subsets as cell markers. In 1982, the concept of CD molecules was proposed and established in the First International Workshop on Human Leukocyte Differentiation Antigens. Cells can be described with a '+' or a '-' symbol to indicate the expression state of CD molecules. For example, a "CD34+, CD31-" cell means that the cell expresses CD34, but don’t express CD31.
CD molecules can function in numerous ways, and they often act as important receptors or ligands to cells. There are more than 360 CD molecules have been identified (as of 2014) and many cells express more than one type of CD markers. CD molecules are consisting of four general types. The first type of CD molecules is transmembrane proteins with their COOH-termini in the cytoplasm and NH2-termini outside the cell. Relatively, the second type of CD molecules is transmembrane proteins with their NH2-termini in the cytoplasm and their COOH-termini outside the cell. The third type of CD molecules is transmembrane proteins cross the plasma membrane more than once forming transmembrane channels. The fourth type of CD molecules is glycosylphosphatidylinositol-anchored proteins tethered to the lipid bilayer by a glycosylphosphatidylinositol anchor.
As a primary manufacturer of recombinant proteins, Creative Biomart provides CD molecules of several sources, grades and formulations for research applications.