Cluster of differentiation

From Freepedia

Cluster of differentiation (CD) molecules are markers on the cell surface, as recognized by specific sets of antibodies, used to identify the cell type, stage of differentiation and activity of a cell.

Contents 1 Nomenclature 2 Uses 3 Some prominent examples 4 External links

Nomenclature

The CD 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. This system was intended for the classification of the many monoclonal antibodies (mAbs), generated by different laboratories around the world, against various surface molecules (antigens) on leukocytes (white blood cells). Since then, the use has expanded to many other cell types, and more than 250 CD clusters and subclusters have been identified. The HLDA workshops assign each CD based on the same reactivity to one human antigen by at least two mAbs; the provisional indicator "w" (as in "CDw186") is sometimes given to a cluster not well characterized or represented by only one mAb.

Uses

CD molecules are often referred to when sorting cells by flow cytometry. A '+' or a '–' symbol is used to indicate if a certain fraction of cells possesses or lacks a CD molecule, e.g. "CD34+, CD31–" = expressing CD34, but not CD31.

The most commonly referred to CD molecules are CD4 and CD8, which are markers for two different sub-types of T-lymphocytes, for the most part (Dendritic cells also express CD8). The relative abundance of CD4+ and CD8+ T cells is often used to monitor the progression of an HIV infection.

CD molecules are not merely markers on the cell surface. Not every CD molecule has been thoroughly characterised, but most of them bring important features to the cells that carry them.

Some prominent examples

• CD1 = an MHC-like molecule that presents lipid molecules
• CD2 = a type I transmembrane protein found on thymocytes, T cells, and some natural killer cells that acts as a ligand for CD58 and CD59 and is involved in signal transduction and cell adhesion; expressed in T-cell acute lymphoblastic leukemia and T-cell lymphoma.
• CD3 = the signaling component of the T cell receptor (TCR) complex
• CD4 = a co-receptor for MHCII; also a receptor used by HIV to enter T cells
• CD5 = a type I transmembrane protein found on T cells, thymocytes, and some B cells that is a ligand for CD72 and is involved in cellular activation or adhesion; expressed in B-cell chronic lymphocytic leukemia and T-cell lymphoma.
• CD7 = a type I transmembrane protein found on thymocytes, some T cells, monocytes, natural killer cells, and hemopoietic stem cells; expressed in patients with mycosis fungoides, some patients with T-cell acute lymphoblastic lymphoma, and a few patients with acute nonlymphocytic lymphoma.
• CD8 = a co-receptor for MHCI; also found on a subset of myeloid dendritic cells.
• CD10 = a type II transmembrane protein found on pre-B cells, germinal-center B cells, some neutrophils, kidney cells, T-cell precursors, and epithelial cells that acts as a zinc metalloprotease cleaving peptide bonds on the amino side of hydrophobic amino acids; expressed in acute lymphocytic leukemia and follicular-center-cell lymphomas.
• CD11c = a type I transmembrane protein found on monocytes, macrophages, neutrophils, and some B cells that induces cellular activation and helps trigger neutrophil respiratory burst; expressed in hairy cell leukemias, acute nonlymphocytic leukemias, and some B-cell chronic lymphocytic leukemias.
• CD15 = a phosphatidylinositol-anchored transmembrane protein found on neutrophils and which may be involved in phagocytosis; expressed in patients with Hodgkin disease, some B-cell chronic lymphocytic leukemias, acute lymphoblastic leukemias, and most acute nonlymphocytic leukemias.
• CD20 = a type III transmembrane protein found on B cells that forms a calcium channel in the cell wall allowing for the influx of calcium required for cell activation; expressed in B-cell lymphomas, hairy cell leukemia, and B-cell chronic lymphocytic leukemia.
• CD21 = a type I transmembrane protein found on B cells, follicular dendritic cells, pharyngeal and cervical epithelial cells, some thymocytes, and some T cells that plays a role in signal transduction; expressed in hairy cell leukemia, B-cell lymphoma, and some T-cell acute lymphocytic leukemias.
• CD21 = a type I transmembrane protein found in the cytoplasm of pre-B cells and on the surface of mature B cells that facilitates signal transduction; expressed in patients with hairy cell leukemias and in some with B-cell lymphomas.
• CD23 = a type II transmembrane protein found on mature B cells, monocytes, activated macrophages, eosinophils, platelets, and dendritic cells that enhances capture and processing of antigen complexed with IgE.
• CD25 = a type I transmembrane protein present on activated T cells, activated B cells, some thymocytes, myeloid precursors, and oligodendrocytes that associates with CD122 to form a heterodimer that can act as a high-affinity receptor for IL-2; expressed in most B-cell neoplasms, some acute nonlymphocytic leukemias, and neuroblastomas.
• CD30 = a type I transmembrane protein present on activated T and B cells that may play a role in cell activation and/or differentiation; expressed in Hodgkin disease, some T-cell lymphomas, and anaplastic large cell lymphomas.
• CD31 = PECAM-1, a cell adhesion molecule on platelets and endothelial cells
• CD34 = stem cell marker, adhesion, found on hematopoietic precursors (found in high concentrations in umbilical cord blood), capillary endothelium, and embryonic fibroblasts
• CD35 = Complement receptor 1 (C3b/C4b receptor)
• CD36 = Platelet glycoprotein IV or IIIb (GP IV / GP IIIb)
• CD38 = involved in ecto-ADP-ribosyl cyclase and cell activation on many hematopoietic, plasma, and B & T activated cells; marker increases with HIV seroconversion, coexpression with CD8 associated with progression (indicates persistent viral stimulation)
• CD45 = a type I transmembrane protein present on all hemopoietic cells except erythrocytes that assists in cell activation; expressed in lymphomas, B-cell chronic lymphocytic leukemia, hairy cell leukemia, and acute nonlymphocytic leukemia.
• CD56 = a marker for natural killer cells and some T-lymphocytes
• CD58 = a membrane protein present on many hemopoietic cells and fibroblasts that acts as a ligand for CD2 and may be involved in T-cell function.
• CD71 = Transferrin receptor, mediates cellular uptake of iron
• CD103 = a type I transmembrane protein present on intestinal intraepithelial lymphocytes, some circulating leukocytes, and some T cells that facilitates adhesion to epithelia; expressed in hairy cell leukemia and some B-cell chronic lymphocytic leukemias.
• CD117 = c-kit, the receptor for Stem Cell Factor, a glycoprotein that regulates cellular differentiation, particularly in hematopoiesis
• CD120 = a receptor for Tumour Necrosis Factor, an inflammatory cytokine
• CD142 = Tissue factor, a major initiator of blood-clotting
• CD143 = Angiotensin-converting enzyme
• CD144 = VE-Cadherin, a calcium-dependent adhesion molecule at intercellular junctions, found mainly in the vascular endothelium. Recent research indicates that CD144 may be present on some leucocytes as well.
• CDw186 = CXCR6, a G-protein-coupled receptor for the neutrophil-attacting chemokine CXCL6
• CD202a = Tie2, the receptor for angiopoietins, a family of angiogenic factors
• CD235a = Glycophorin, a protein on blood cells

External links

• HLDA Antibody Database
• A list of CD molecules, at ebioscience.com
• Another list of CD molecules, at Expasy.org
• Yet another list of CD molecules, at PathologyOutlines.com