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Cluster of Differentiation (CD)

Sino Biological offers a comprehensive set of tools for Cluster of Differentiation (CD) molecule related research, including proteins, antibodies, ELISA kits, and cDNA clones.

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    Cluster of Differentiation (CD) Background

    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 cluster of differentiation nomenclature was proposed and established in the 1st International Workshop and Conference on Human Leukocyte Differentiation Antigens (HLDA), which was held in Paris in 1982. Immunologists generated large numbers of monoclonal antibodies reactive with leukocyte cell-surface molecules, each with different associated nomenclatures. In the absence of comparative studies it was often impossible to tell if the same molecule was recognized by more than one antibody. The approach of the workshops was to code antibodies and to send them to multiple participating laboratories for blind analysis against multiple cell types. The data were collated and analyzed by the statistical procedure of "cluster analysis." This analytical method identified clusters of antibodies with very similar patterns of binding to leukocytes at various stages of differentiation: hence the "cluster of differentiation" (CD) nomenclature. The cluster of differentiation nomenclature allowed the scientific community to communicate results in a universal language.

    The cluster of differentiation nomenclature describes different monoclonal antibodies from different sources that recognize identical antigens. The proposed surface molecule is assigned a CD number once two specific monoclonal antibodies are shown to bind to the molecule. A small letter w before the number designation stands for "workshop", which indicates that the CD designation is tentative.

    The cluster of differentiation antigens are membrane proteins mainly expressed on leukocytes. A small number are also expressed on endothelial cells, erythrocytes, and stem cells. Cluster of differentiation antigens are commonly used as cell markers, allowing cells to be defined based on what molecules are present on their surface. For example, two commonly-used CD molecules are CD4 and CD8, which are, in general, used as markers for two different subtypes of T-lymphocytes, helper and cytotoxic T cells, respectively. CD4 is specifically recognized and bound by HIV, leading to viral infection and destruction of CD4+ T cells. The relative abundance of CD4+ and CD8+ T cells is often used to monitor the progression of an HIV infection. Detection the expression of cluster of differentiation (CD) antigens is supposed to be developed as diagnosis methods in some diseases, such as cardiovascular disease, and tumors.

    Lal and colleagues reported a novel fluorescence-based antibody array system to detect microparticles from acute coronary syndrome patients based on cluster of differentiation (CD) antigen expression. Microparticles that circulate in plasma express cluster of differentiation (CD) antigens and are present at elevated levels in patients with acute coronary syndrome. Isolated microparticles are captured on anti-CD antibody spots immobilized on a nitrocellulose membrane. These cluster of differentiation (CD) antibodies are directed against extracellular epitopes, whereas the intracellular exposed surface of the microparticles is labeled with a fluorescent anti-annexin antibody. The array is then scanned and quantified. A pilot study was undertaken to compare microparticle cluster of differentiation (CD) antigen expression in acute coronary syndrome and healthy subjects. Ten cluster of differentiation (CD) antigens: 44, 45, 54, 62E, 79, 102, 117, 130, 138, and 154 had significantly increased expression in the disease group relative to the healthy controls.

    Another study suggested a potential association between a low expression level of cluster differentiation 9 and malignant parotid gland tumors. A statistically significantly reduced expression of cluster of differentiation 9 in malignant parotid gland tumors was observed, compared with benign parotid gland tumors (p < 0.05).

    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.

    Cluster of Differentiation (CD) References

    1. Zola H, et al. (2005) CD molecules 2005: human cell differentiation molecules. Blood. 106(9):3123-6.
    2. Woolfson A, et al. (2006) The application of CD antigen proteomics to pharmacogenomics. Pharmacogenomics 7(5):759-71.
    3. Ellmark P, et al. (2008) The applicability of a cluster of differentiation monoclonal antibody microarray to the diagnosis of human disease. Methods Mol Biol. 439:199-209.
    4. Sakamoto K, et al. (2009) Expression of cluster of differentiation 9 glycoprotein in benign and malignant parotid gland tumours. J Laryngol Otol Suppl. (31):58-63.
    5. Sakamoto K, et al. (2009) Expression of cluster of differentiation 9 glycoprotein in benign and malignant parotid gland tumours. J Laryngol Otol Suppl. (31):58-63.
    6. Lal S, et al. (2009) Using antibody arrays to detect microparticles from acute coronary syndrome patients based on cluster of differentiation (CD) antigen expression. Mol Cell Proteomics. 8(4):799-804.