antibody

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antibody,

protein produced by the immune system (see immunityimmunity,
ability of an organism to resist disease by identifying and destroying foreign substances or organisms. Although all animals have some immune capabilities, little is known about nonmammalian immunity.
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) in response to the presence in the body of antigens: foreign proteins or polysaccharides such as bacteria, bacterial toxinstoxin,
poison produced by living organisms. Toxins are classified as either exotoxins or endotoxins. Exotoxins are a diverse group of soluble proteins released into the surrounding tissue by living bacterial cells. Exotoxins have specific reaction sites in the host; e.g.
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, viruses, or other cells or proteins. Such antigens are capable of inflicting damage by chemically combining with natural substances in the body and disrupting the body's processes. The body contains hundreds of thousands of different white blood cells called B lymphocytes, each capable of producing one type of antibody and each bearing sites on its membrane that will bind with a specific antigen. When such a binding occurs, it triggers the B lymphocyte to reproduce itself, forming a cloneclone,
group of organisms, all of which are descended from a single individual through asexual reproduction, as in a pure cell culture of bacteria. Except for changes in the hereditary material that come about by mutation, all members of a clone are genetically identical.
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 that manufactures vast amounts of its antibody.

The antibody molecule is composed of four polypeptide chains (see peptidepeptide,
organic compound composed of amino acids linked together chemically by peptide bonds. The peptide bond always involves a single covalent link between the α-carboxyl (oxygen-bearing carbon) of one amino acid and the amino nitrogen of a second amino acid.
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)—two identical light chains and two identical heavy chains—joined by disulfide bridges. The light chains have a variable portion that is different in each type of antibody and is the active portion of the molecule that binds with the specific antigen. Antibodies combine with some antigens, such as bacterial toxins, and neutralize their effect; they remove other substances from circulation in body fluids; they bind certain antigens together, a process known as agglutination; and they activate complement, blood serum proteins that cause the destruction of invading cells.

See also monoclonal antibodymonoclonal antibody,
an antibody that is mass produced in the laboratory from a single clone and that recognizes only one antigen. Monoclonal antibodies are typically made by fusing a normally short-lived, antibody-producing B cell (see immunity) to a fast-growing cell, such as
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.

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Antibody

A protein found principally in blood serum and characterized by a specific reactivity with the corresponding antigen. Antibodies are important in resistance against disease, in allergy, and in blood transfusions, and can be utilized in laboratory tests for the detection of antigens or the estimation of immune status.

Antibodies are normally absent at birth unless derived passively from the mother through the placenta or colostrum. In time, certain antibodies appear in response to environmental antigens. Antibodies are also induced by artificial immunization with vaccines or following natural infections. The resulting antibody level declines over a period of months, but rapidly increases following renewed contact with specific antigen, even after a lapse of years. This is known as an anamnestic or booster response. See Allergy, Blood groups, Hypersensitivity, Isoantigen, Vaccination

Antibody reactivity results in precipitation of soluble antigens, agglutination of particulate antigens, increased phagocytosis of bacteria, neutralization of toxins, and dissolution of bacterial or other cells specifically sensitive to their action; the antibodies so revealed are termed precipitins, agglutinins, opsonins, antitoxins, and lysins. One antibody may give many such reactions, depending on conditions, so these classifications are not unique or exclusive.

Three principal groups (IgG, IgM, IgA) and two minor groups (IgD, IgE) of antibodies are recognized. These all form part of the wider classification of immunoglobulins. Antibody diversity is generated by amino acid substitutions that result in unique antigen-binding structures. See Cellular Immunology, Immunoglobulin

The development of the technology for producing monoclonal antibodies, which can bind to specific sites on target antigens, revolutionized the uses of antibodies in biology and medicine. Unfortunately, almost all monoclonal antibodies originate in mice, and the murine immunoglobulin serves as an antigen, frequently acting immunogenic in human recipients. See Antigen, Monoclonal antibodies

McGraw-Hill Concise Encyclopedia of Bioscience. © 2002 by The McGraw-Hill Companies, Inc.

antibody

[′an·tə‚bäd·ē]
(immunology)
A protein, found principally in blood serum, originating either normally or in response to an antigen and characterized by a specific reactivity with its complementary antigen. Also known as immune body.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

antibody

any of various proteins produced in the blood in response to the presence of an antigen. By becoming attached to antigens on infectious organisms antibodies can render them harmless or cause them to be destroyed
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005
References in periodicals archive ?
Tdap should replace 1 dose of Td, preferably between 27 and 36 weeks gestation to maximize the maternal antibody response and passive antibody transfer to the infant.
Alford, "The outcome of congenital cytomegalovirus infection in relation to maternal antibody status," The New England Journal of Medicine, vol.
Congenital rubella syndrome due to infection after maternal antibody conversion with vaccine.
In our study titre of maternal antibody in ABO HDFN was positively correlated with grades of DAT, risk related to peak bilirubin levels, severity of disease and intensity of treatment and was negatively correlated with cord blood haemoglobin levels.
Maternal antibody transferred to the young infant has an antibody half-life that provides adequate protection during the first 2 months of life, when the infant is especially vulnerable to pertussis infection.
Antibody titers of chicks in unvaccinated controls Group E: On day 07, a total of 10 chicks had maternal antibody titer of 1: 2 each; 07 chicks a titer of 1: 4 and of 03 chicks each indicated a titer of 1: 8 H9N2 virus.
The significant differences observed in maternal antibody negative (ab-) chickens were not significant in maternal antibody positive (ab+) chickens, demonstrating the requirement of ab- birds for this type of comparison.
Defined as the first maternal episode but antibody to detected HSV type is not present (e.g., HSV-2 confirmed from lesion, with type 1 but NOT type 2 maternal antibody present; OR HSV-1 confirmed, with type 2 but NOT type 1 maternal antibody present), the risk of neonatal infection is approximately 25%.
Protection against bovine respiratory syncytial virus challenge following a single dose of vaccine in young calves with maternal antibody. Veterinary Record, v.156, p.139-143, 2005.
"Since the adenovirus is of human origin, livestock have no maternal antibody resistance to it," he explains.
Treanor, director of the University of Rochester (N.Y.) vaccine and treatment evaluation unit, noted "It's a question of how much you gain from maternal antibody versus what you lose by suppression.

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