The cluster of differentiation (also known as cluster of designation or classification determinant and often abbreviated as CD ) is a protocol used for the identification and investigation of cell surface molecules providing targets for immunophenotyping of cells. In terms of physiology, CD molecules can act in numerous ways, often acting as receptors or ligands important to the cell. A signal cascade is usually initiated, altering the behavior of the cell (see cell signaling ). Some CD proteins do not play a role in cell signaling, but have other functions, such as cell adhesion . CD for humans is numbered up to 371 (as of 21 April 2016 ).
33-487: 6693 20737 ENSG00000197471 ENSMUSG00000051457 P16150 P15702 NM_001030288 NM_003123 NM_001037810 NM_009259 NP_001025459 NP_003114 NP_001032899 NP_033285 Leukosialin also known as sialophorin or CD43 ( cluster of differentiation 43) is a transmembrane cell surface protein that in humans is encoded by the SPN ( s ialo p hori n ) gene . Sialophorin (leukosialin)
66-410: A chemokine receptor on the surface of a T helper cell to gain entry. The number of CD4 and CD8 T cells in blood is often used to monitor the progression of HIV infection . While CD molecules are very useful in defining leukocytes, they are not merely markers on the cell surface . Though only a fraction of known CD molecules have been thoroughly characterised, most of them have important functions. In
99-578: A stem cell , as opposed to a fully differentiated endothelial cell . Some cell populations can also be defined as , , or (alternatively, , , or ), indicating an overall variability in CD expression , particularly when compared to other cells being studied. A review of the development of T cells in the thymus uses this nomenclature to identify cells transitioning from CD4 /CD8 double-positive cells to CD4 /CD8 . Since 1982 there have been nine Human Leukocyte Differentiation Antigen Workshops culminating in
132-426: A conference. The CD system is commonly used as cell markers in immunophenotyping , allowing cells to be defined based on what molecules are present on their surface. These markers are often used to associate cells with certain immune functions . While using one CD molecule to define populations is uncommon (though a few examples exist), combining markers has allowed for cell types with very specific definitions within
165-416: A high viscosity , for example, in egg white and blood plasma . Variable surface glycoproteins allow the sleeping sickness Trypanosoma parasite to escape the immune response of the host. The viral spike of the human immunodeficiency virus is heavily glycosylated. Approximately half the mass of the spike is glycosylation and the glycans act to limit antibody recognition as the glycans are assembled by
198-725: Is a compound containing carbohydrate (or glycan) covalently linked to protein. The carbohydrate may be in the form of a monosaccharide, disaccharide(s). oligosaccharide(s), polysaccharide(s), or their derivatives (e.g. sulfo- or phospho-substituted). One, a few, or many carbohydrate units may be present. Proteoglycans are a subclass of glycoproteins in which the carbohydrate units are polysaccharides that contain amino sugars. Such polysaccharides are also known as glycosaminoglycans. A variety of methods used in detection, purification, and structural analysis of glycoproteins are The glycosylation of proteins has an array of different applications from influencing cell to cell communication to changing
231-576: Is a major sialoglycoprotein on the surface of human T lymphocytes , monocytes , granulocytes , and some B lymphocytes , which appears to be important for immune function and may be part of a physiologic ligand-receptor complex involved in T-cell activation. Defects in the CD43 molecule are associated with the development of Wiskott–Aldrich syndrome . It also appears in about 25% of intestinal MALTomas. Using immunohistochemistry , CD43 can be demonstrated in
264-494: Is also an effective marker for myeloid tumours. CD43 has been shown to interact with EZR and Moesin . This membrane protein –related article is a stub . You can help Misplaced Pages by expanding it . Cluster of differentiation The CD nomenclature was proposed and established in the 1st International Workshop and Conference on Human Leukocyte Differentiation Antigens (HLDA), held in Paris in 1982. This system
297-424: Is attached to the protein in a cotranslational or posttranslational modification . This process is known as glycosylation . Secreted extracellular proteins are often glycosylated. In proteins that have segments extending extracellularly, the extracellular segments are also often glycosylated. Glycoproteins are also often important integral membrane proteins , where they play a role in cell–cell interactions. It
330-789: Is important to distinguish endoplasmic reticulum-based glycosylation of the secretory system from reversible cytosolic-nuclear glycosylation. Glycoproteins of the cytosol and nucleus can be modified through the reversible addition of a single GlcNAc residue that is considered reciprocal to phosphorylation and the functions of these are likely to be an additional regulatory mechanism that controls phosphorylation-based signalling. In contrast, classical secretory glycosylation can be structurally essential. For example, inhibition of asparagine-linked, i.e. N-linked, glycosylation can prevent proper glycoprotein folding and full inhibition can be toxic to an individual cell. In contrast, perturbation of glycan processing (enzymatic removal/addition of carbohydrate residues to
363-530: Is likely to have been secondary to its role in host-pathogen interactions. A famous example of this latter effect is the ABO blood group system . Though there are different types of glycoproteins, the most common are N -linked and O -linked glycoproteins. These two types of glycoproteins are distinguished by structural differences that give them their names. Glycoproteins vary greatly in composition, making many different compounds such as antibodies or hormones. Due to
SECTION 10
#1732802134461396-450: Is through the reaction between a protected glycan and a protected Asparagine. Similarly, an O-linked glycoprotein can be formed through the addition of a glycosyl donor with a protected Serine or Threonine . These two methods are examples of natural linkage. However, there are also methods of unnatural linkages. Some methods include ligation and a reaction between a serine-derived sulfamidate and thiohexoses in water. Once this linkage
429-542: The body is mucins , which are secreted in the mucus of the respiratory and digestive tracts. The sugars when attached to mucins give them considerable water-holding capacity and also make them resistant to proteolysis by digestive enzymes. Glycoproteins are important for white blood cell recognition. Examples of glycoproteins in the immune system are: H antigen of the ABO blood compatibility antigens. Other examples of glycoproteins include: Soluble glycoproteins often show
462-483: The cell, causing a decrease in drug effectiveness. Therefore, being able to inhibit this behavior would decrease P-glycoprotein interference in drug delivery, making this an important topic in drug discovery. For example, P-Glycoprotein causes a decrease in anti-cancer drug accumulation within tumor cells, limiting the effectiveness of chemotherapies used to treat cancer. Hormones that are glycoproteins include: Quoting from recommendations for IUPAC: A glycoprotein
495-426: The designation (e.g., CD2 molecule). Currently, "CD2" is generally used to designate the molecule, and "CD2 antibody " is used to designate the antibody. Cell populations are usually defined using a '+' or a '−' symbol to indicate whether a certain cell fraction expresses or lacks a CD molecule. For example, a " CD34 +, CD31 −" cell is one that expresses CD34 but not CD31. This CD combination typically corresponds to
528-610: The example of CD4 and CD8, these molecules are critical in antigen recognition. Others (e.g., CD135 ) act as cell surface receptors for growth factors . Recently, the marker CD47 was found to have anti- phagocytic signals to macrophages and inhibit natural killer (NK) cells. This enabled researchers to apply CD47 as a potential target to attenuate immune rejection . Glycoprotein Glycoproteins are proteins which contain oligosaccharide (sugar) chains covalently attached to amino acid side-chains. The carbohydrate
561-420: The glycan), which occurs in both the endoplasmic reticulum and Golgi apparatus , is dispensable for isolated cells (as evidenced by survival with glycosides inhibitors) but can lead to human disease (congenital disorders of glycosylation) and can be lethal in animal models. It is therefore likely that the fine processing of glycans is important for endogenous functionality, such as cell trafficking, but that this
594-535: The host cell and so are largely 'self'. Over time, some patients can evolve antibodies to recognise the HIV glycans and almost all so-called 'broadly neutralising antibodies (bnAbs) recognise some glycans. This is possible mainly because the unusually high density of glycans hinders normal glycan maturation and they are therefore trapped in the premature, high-mannose, state. This provides a window for immune recognition. In addition, as these glycans are much less variable than
627-509: The immune system. CD molecules are utilized in cell sorting using various methods, including flow cytometry . Two commonly used CD molecules are CD4 and CD8 , which are, in general, used as markers for helper and cytotoxic T cells, respectively. These molecules are defined in combination with CD3+, as some other leukocytes also express these CD molecules (some macrophages express low levels of CD4; dendritic cells express high levels of CD8). Human immunodeficiency virus binds CD4 and
660-409: The molecule. If the molecule has not been well characterized or has only one mAb, it is usually given the provisional indicator "w" (as in " CDw186 "). For instance, CD2 mAbs are reagents that react with a 50‐kDa transmembrane glycoprotein expressed on T cells . The CD designations were used to describe the recognized molecules but had to be clarified by attaching the term antigen or molecule to
693-469: The most common cell line used for recombinant glycoprotein production is the Chinese hamster ovary line. However, as technologies develop, the most promising cell lines for recombinant glycoprotein production are human cell lines. The formation of the link between the glycan and the protein is key element of the synthesis of glycoproteins. The most common method of glycosylation of N-linked glycoproteins
SECTION 20
#1732802134461726-706: The most common. Monosaccharides commonly found in eukaryotic glycoproteins include: The sugar group(s) can assist in protein folding , improve proteins' stability and are involved in cell signalling. The critical structural element of all glycoproteins is having oligosaccharides bonded covalently to a protein. There are 10 common monosaccharides in mammalian glycans including: glucose (Glc), fucose (Fuc), xylose (Xyl), mannose (Man), galactose (Gal), N- acetylglucosamine (GlcNAc), glucuronic acid (GlcA), iduronic acid (IdoA), N-acetylgalactosamine (GalNAc), sialic acid , and 5- N-acetylneuraminic acid (Neu5Ac). These glycans link themselves to specific areas of
759-539: The paracortical T-cells of healthy lymph nodes and tonsils; it is also positive in a range of lymphoid and myeloid tumours. Although it is present in over 90% of T-cell lymphomas , it is generally less effective at demonstrating this condition than is CD3 antigen. However, it may be useful as part of a panel to demonstrate B-cell lymphoblastic lymphoma , since the malignant cells in this condition are often CD43 positive, and may be difficult to stain with other antibodies. Because it stains granulocytes and their precursors, it
792-471: The production of the protein. Glycosylation is a process that roughly half of all human proteins undergo and heavily influences the properties and functions of the protein. Within the cell, glycosylation occurs in the endoplasmic reticulum . There are several techniques for the assembly of glycoproteins. One technique utilizes recombination . The first consideration for this method is the choice of host, as there are many different factors that can influence
825-488: The protein amino acid chain. The two most common linkages in glycoproteins are N -linked and O -linked glycoproteins. An N -linked glycoprotein has glycan bonds to the nitrogen containing an asparagine amino acid within the protein sequence. An O -linked glycoprotein has the sugar is bonded to an oxygen atom of a serine or threonine amino acid in the protein. Glycoprotein size and composition can vary largely, with carbohydrate composition ranges from 1% to 70% of
858-487: The purposes of this field of study is to determine which proteins are glycosylated and where in the amino acid sequence the glycosylation occurs. Historically, mass spectrometry has been used to identify the structure of glycoproteins and characterize the carbohydrate chains attached. The unique interaction between the oligosaccharide chains have different applications. First, it aids in quality control by identifying misfolded proteins. The oligosaccharide chains also change
891-405: The solubility and polarity of the proteins that they are bonded to. For example, if the oligosaccharide chains are negatively charged, with enough density around the protein, they can repulse proteolytic enzymes away from the bonded protein. The diversity in interactions lends itself to different types of glycoproteins with different structures and functions. One example of glycoproteins found in
924-493: The success of glycoprotein recombination such as cost, the host environment, the efficacy of the process, and other considerations. Some examples of host cells include E. coli, yeast, plant cells, insect cells, and mammalian cells. Of these options, mammalian cells are the most common because their use does not face the same challenges that other host cells do such as different glycan structures, shorter half life, and potential unwanted immune responses in humans. Of mammalian cells,
957-403: The thermal stability and the folding of proteins. Due to the unique abilities of glycoproteins, they can be used in many therapies. By understanding glycoproteins and their synthesis, they can be made to treat cancer, Crohn's Disease , high cholesterol, and more. The process of glycosylation (binding a carbohydrate to a protein) is a post-translational modification , meaning it happens after
990-543: The total mass of the glycoprotein. Within the cell, they appear in the blood, the extracellular matrix , or on the outer surface of the plasma membrane, and make up a large portion of the proteins secreted by eukaryotic cells. They are very broad in their applications and can function as a variety of chemicals from antibodies to hormones. Glycomics is the study of the carbohydrate components of cells. Though not exclusive to glycoproteins, it can reveal more information about different glycoproteins and their structure. One of
1023-402: The underlying protein, they have emerged as promising targets for vaccine design. P-glycoproteins are critical for antitumor research due to its ability block the effects of antitumor drugs. P-glycoprotein, or multidrug transporter (MDR1), is a type of ABC transporter that transports compounds out of cells. This transportation of compounds out of cells includes drugs made to be delivered to
CD43 - Misplaced Pages Continue
1056-400: The wide array of functions within the body, interest in glycoprotein synthesis for medical use has increased. There are now several methods to synthesize glycoproteins, including recombination and glycosylation of proteins. Glycosylation is also known to occur on nucleo cytoplasmic proteins in the form of O -GlcNAc . There are several types of glycosylation, although the first two are
1089-461: Was intended for the classification of the many monoclonal antibodies (mAbs) generated by different laboratories around the world against epitopes on the surface molecules of leukocytes (white blood cells). Since then, its use has expanded to many other cell types, and more than 370 CD unique clusters and subclusters have been identified. The proposed surface molecule is assigned a CD number once two specific monoclonal antibodies are shown to bind to
#460539