opsonin

op·so·nin

O0100000 (ŏp′sə-nĭn)n. A substance, such as an antibody or complement protein, that binds to a bacterium or other pathogen and causes it to become more susceptible to the action of phagocytes.

[Latin opsōnāre, to buy provisions (from Greek opsōnein, from opson, condiment, delicacy; see epi in Indo-European roots) + -in.]

opsonin

(ˈɒpsənɪn) n (Biochemistry) a constituent of blood serum that renders invading bacteria more susceptible to ingestion by phagocytes in the serum[C20: from Greek opsōnion victuals] opsonic adj

op•so•nin

(ˈɒp sə nɪn)

n. any of several constituents of blood serum, as an antibody or complement, that make invading microorganisms more susceptible to destruction by phagocytes. [1900–05; < Latin opsōn(ium) victuals] op•son•ic (ɒpˈsɒn ɪk) adj.

Thesaurus

Noun

opsonin - an antibody in blood serum that attaches to invading microorganisms and other antigens to make them more susceptible to the action of phagocytesblood serum, serum - an amber, watery fluid, rich in proteins, that separates out when blood coagulatesantibody - any of a large variety of proteins normally present in the body or produced in response to an antigen which it neutralizes, thus producing an immune response

Translations

Opsonin

enUK

opsonin

[′äp·sə·nən] (immunology) A substance in blood serum that renders bacteria more susceptible to phagocytosis by leukocytes.

Opsonin

a type of antibody. Opsonins are immunoglobulins of the G class (IgG) and are largely responsible for the body’s resistance to bacteria, viruses, and tumors (seeIMMUNOGLOBULINS).

The British scientists A. Wright and S. Douglas introduced the term “opsonin” in 1903 to denote humoral factors in the blood that facilitate and stimulate the phagocytosis of bacteria by leukocytes. The cytophil portion of the opsonin molecule has an affinity for the plasma membrane of phagocytes. When opsonins combine with bacterial or viral antigens or with foreign macromolecules, the cytophil portion becomes exposed and attached to the surface of a phagocyte. An opsonin promotes the adhesion reaction and the absorption and destruction of a particle by reducing the energy of the surface interaction between the leukocyte and the object of phagocytosis. This reduction of energy can be accomplished, for example, by decreasing the repulsive electrostatic forces between the leukocyte and the foreign body.

Immunoglobulins of the M class (IgM) can also act as opsonins in the presence of complement (seeCOMPLEMENT). The first five components of complement greatly enhance the ability of IgG to act as an opsonin. In addition to humoral antibodies, cytophil antibodies that are fixed on certain phagocytes are opsonins. Like complement, fibrin and a polypeptide that is released by lymphocytes upon contact with certain antigens act as nonspecific opsonins. Although insects do not have immunoglobulins or phagocytes with IgG receptors, the hemolymph of insects does contain specific opsonin proteins.

Opsonins are responsible for selectivity, an important property of the phagocytic reaction. Because of opsonins, a phagocyte recognizes and attacks only foreign substances, not its own macromolecules. Some bacterial substances, for example, polysaccharides of pneumococci and meningococci and proteins of streptococci, are able to suppress the phagocytic activity of leukocytes. Antibodies to these suppressor substances perform the function of opsonins. Virulent strains of staphylococci and Escherichia coli release a specific protein that can block the cytophil portion of an opsonin, thereby inhibiting phagocytosis. Along with complement, thrombocytes, and phagocytes, opsonins neutralize foreign substances and microbes.

A. N. MATS

opsonin

[op´sŏ-nin] an antibody that renders bacteria and other cells susceptible to phagocytosis. adj., adj opson´ic.immune opsonin an antibody that sensitizes a particulate antigen to phagocytosis.

op·so·nin

(op'sŏ-nin), Any blood serum protein that binds to antigens, enhancing phagocytosis (for example, C3b of the complement system, specific antibodies). [G. opson, boiled meat, provisions, fr. hepsō, to boil, + -in]

opsonin

(ŏp′sə-nĭn)n. An antibody or product of complement activation in blood serum that causes bacteria or other foreign cells to become more susceptible to the action of phagocytes.

op·so·nin

(op'sŏ-nin) A substance that binds to antigens, enhancing phagocytosis. [G. opson, boiled meat, provisions, fr. hepsō, to boil, + -in]

opsonin

One of a number of substances, especially an antibody, naturally present in the blood that bind to the surface of bacteria to make them more readily susceptible to attack and destruction by PHAGOCYTES.

opsonin

a type of ANTIBODY which binds to ANTIGENS, increasing their susceptibility to phagocytosis by other antibodies.

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Words related to opsonin

noun an antibody in blood serum that attaches to invading microorganisms and other antigens to make them more susceptible to the action of phagocytes

Related Words