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Encyclopedia > Opsonin

An opsonin is any molecule that acts as a binding enhancer for the process of phagocytosis, for example, by coating the negatively-charged molecules on the membrane. Both the membrane of a phagocytising cell, as well as its next meal, have a negative charge (Zeta-potential), making it difficult for the two cells to come close together. During the process of opsonization, antigens are bound by antibody and/or complement molecules. Phagocytic cells express receptors that bind opsonin molecules. With the antigen coated in these molecules, binding of the antigen to the phagocyte is greatly enhanced. Most phagocytic binding cannot occur without opsonization of the antigen. Phagocytosis (literally, cell eating) is a form of endocytosis where large particles are enveloped by the cell membrane of a (usually larger) cell and internalized to form a phagosome, or food vacuole. ... An antigen is a molecule that stimulates the production of antibodies. ... Schematic of antibody binding to an antigen An antibody is a protein used by the immune system to identify and neutralize foreign objects like bacteria and viruses. ... The complement system is derived from many small plasma proteins that form the complex biochemical cascade of the immune system. ...


Furthermore, opsonization of the antigen and subsequent binding to an activated phagocyte will cause increased expression of complement receptors on neighboring phagocytes. Examples of opsonin molecules include the IgG antibody and the C3b, C4b, and iC3b components of the complement system. Schematic of antibody binding to an antigen An antibody is a protein complex used by the immune system to identify and neutralize foreign objects like bacteria and viruses. ... The complement system is derived from many small plasma proteins that form the complex biochemical cascade of the immune system. ...


See also

Antibody opsonization. When a pathogen is recognized by free floating antibodies, they bind to it to opsonize it. ...


  Results from FactBites:
 
opsonin: Definition and Much More from Answers.com (461 words)
Opsonin is generally synonymous with the bacteri-otropin of F. Neufeld and coworkers (1904–1905), a relatively thermostable antibody, increased in amount during specific immunization, that renders the corresponding bacterium more susceptible to phagocytosis.
An opsonin is any molecule that acts as a binding enhancer for the process of phagocytosis, for example, by coating the negatively-charged molecules on the membrane.
During the process of opsonization, antigens are bound by antibody and/or complement molecules.
Patent 6,224,870 (812 words)
In another embodiment of the invention, where a first and second portion of an opsonin, when covalently associated via a non-peptide bond, form an APC binding domain, them first or second portion of the opsonin may be fused in-frame to the antigen to form a fusion polypeptide.
Therefore, in another aspect, the invention pertains to a multichain polypeptide complex comprising a first portion of an innate opsonin which in the presence of a second portion of an innate opsonin forms an APC binding domain, and a fusion polypeptide that comprises an antigen and the second portion of the opsonin.
The first portion of the innate opsonin is associated with the fusion polypeptide containing the second portion of the opsonin via a covalent linkage.
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