Cell differentiation antigens cluster

Cell differentiation antigens (cluster of differentiation, CD) 187,407 Cell membranes 3... 

C23. Cobbold, S., Hale, G., and Waldmann, H., Non-lineage, LFA-1 family, and leucocyte common antigens New and previously defined clusters. In Leukocyte Typing III White Cell Differentiation Antigens (A. J. McMichael, P. C. L. Beverley, S. Cobbolds, etal., eds.), pp. 788-804. Oxford University Press, Oxford, 1987. 

The terminology for lymphoma immunophenotyping differs slightly from that of many other tumor types. The cell surface antigens of leukocytes have been assigned cluster of differentiation (CD) designations, each of which... 

Immune Defense. Figure 3 Drugs involved in suppressing innate and adaptive immune response. Abbreviations mob monoclonal antibody, TCR T-cell antigen receptor, IL-2 interleukin-2, R receptor, CD cluster of differentiation. 

Key PMN, polymorphonuclear leukocytes EC, endothelial cell lymphs, lymphocytes CD, cluster of differentiation iCAM, intercellular adhesion molecule LFA-1, lymphocyte function-associated antigen-1 PECAM-1, platelet endothelial cell adhesion cell molecule-1. 

The cell surface contains antigens, which are referred to as CD, which stands for cluster of differentiation. The antibodies are produced against a specific antigen. When administered, usually by an intravenous injection, the antibody binds to the antigen, which may trigger the immune system to result in cell death through complement-mediated cellular toxicity, or the antigen-antibody cell complex may be internalized to the cancer cell, which results in cell death. Monoclonal antibodies also may carry radioactivity, sometimes referred to as hot antibodies, and may be referred to as radioimmunotherapy, so the radioactivity is delivered to the cancer cell. Antibodies that contain no radioactivity are referred to as cold antibodies. 

B cells are produced by the bone marrow. In response to activation of CD4+ T helper cells (see below), B cells proliferate and produce antibodies. (The term CD stands for cluster of differentiation. They are proteins coating cell surfaces. Altogether, there are more than 160 different types of CDs.) The antibodies produced by B cells circulate in the bloodstream and bind to antigens. Once bound, other cells are in turn activated to destroy the antigens. 

Immunoglobulin M (IgM), a membrane protein on the surface of B lymphocytes, serves to bind free antigens to the B cells. By contrast, T cell receptors only bind antigens when they are presented by another cell as a complex with an MHC protein (see below). Interaction between MHC-bound antigens and T cell receptors is supported by co-recep-tors. This group includes CDS, a membrane protein that is typical in cytotoxic T cells. T helper cells use CD4 as a co-receptor instead (not shown). The abbreviation CD stands for cluster of differentiation. It is the term for a large group of proteins that are all located on the cell surface and can therefore be identified by antibodies. In addition to CD4 and CDS, there are many other co-receptors on immune cells (not shown). 

CD4+ Cluster of differentiation 4 Transmembrane glycoprotein expressed on surface of some immune cells, interacts with antigen-presenting cell... 

ADA Adenosine deaminase ALG Antilymphocyte globulin APC Antigen-presenting cell ATG Antithymocyte globulin CD Cluster of differentiation CSF Colony-stimulating factor CTL Cytotoxic T lymphocyte DC Dendritic cell... 

It is relevant to explain the use of the letters CD as a prefix to monoclonal antibodies. Lymphocytes possess many different surface proteins, each of which possesses many distinct epitopes. To classify these lymphocyte antigens, a numbering system has been established that clusters molecules having similar epitopes. Thus, all monoclonal antibodies that detect the epitopes on a single antigen are assigned to a numbered cluster of differentiation (CD). In most cases a defined CD denotes a protein of specific function. For example, the protein called CD4 is associated with cells (lymphocytes) that help the immune response, while CD8 is found on cells that suppress the immune response. 

Schematic representation of the mesenchymal and endothelial cascade of differentiation in a murine model (mice) and in humans (hum). All mesenchymal and endothelial cells are negative for the antigen CD45. Based on this, the dynamics of surface antigen expression along development of different mature cells derived from the mesenchymal and endothelial systems can be observed. Rounded arrows indicate selfrenewal potential. Smooth, thinner arrows indicate directions of cellular differentiation, and dotted arrows indicate possible hierarchies, but yet to be proved experimentally. The question marks indicate lack of data on the pathway or on cellular identity. The identification of CDs (clusters of differentiation) and other antigen cell markers can be found in the list of abbreviations LT-HSC, long-term hematopoietic stem cell EC, endothelial cell PDMPC, placental-derived mesenchymal progenitor cell MSC, mesenchymal stem cell MAPC, mesenchymal adult progenitor cell.

Monoclonal antibodies may be used as passive immunotherapy to treat malignancies. They react with specific antigens present on the surface of tumor cells and result in cell destruction. Rituximab was the first MoAb approved in the United States for the treatment of cancer. It is a chimeric MoAb directed against cluster differentiation 20 (CD20) markers, which are expressed on over 90% of B-cell NHL tumors. Rituximab is thought to result in B-cell depletion by a number of mechanisms, including complement-mediated and antibody-dependent cell lysis and induction of apoptosis. 

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