Cluster of differentiation
The cluster of differentiation (or cluster of designation), often abbreviated as CD, is a protocol used for the identification and investigation of cell surface molecules present on white blood cells (cells of the immune system). The cluster of differentiation nomenclature was proposed for the classification of the many monoclonal antibodies (mAbs) generated by different laboratories around the world against epitopes on the surface molecules of leukocytes. Since then, the use of cluster of differentiation has expanded to many other cell types, and for humans CD is numbered up to 350 most recently (as of 2009)
The human cluster of differentiation (CD) antigens constitute a promising assay content for antibody microarray applications, because of their common expression at the leukocyte cell surface and the fact that the majority perform critical functions in the human immune response. The diagnostic potential of a microarray, containing 82 cluster of differentiation monoclonal antibodies (DotScan microarrays) has been demonstrated for a variety of infectious and neoplastic disease states, including HIV, many acute and chronic leukemias, and colorectal cancer. It is likely that these cluster of differentiation monoclonal antibody microarrays will have more general utility that extends to other pathological categories, including autoimmune, metabolic, and degenerative diseases.
Cluster of differentiation antigens are not merely markers on the cell surface. Cluster of differentiation antigens can act in numerous ways and are important for immune reactions of organisms. They often act as receptors or ligands important to the cell, initiating a signal cascade and altering the behavior of the cell. Some cluster of differentiation antigens do not play a role in cell signaling, but have other functions, such as cell adhesion.