antigen

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antigen:

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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Antigen

A substance that initiates and mediates the formation of the corresponding immune body, termed antibody. Antigens can also react with formed antibodies. Antigen-antibody reactions serve as host defenses against microorganisms and other foreign bodies, or are used in laboratory tests for detecting the presence of either antigen or antibody. See Antibody, Antigen-antibody reaction

A protein immunogen (any substance capable of inducing an immune response) is usually composed of a large number of antigenic determinants. Thus, immunizing an animal with a protein results in the formation of a number of antibody molecules with different specificities. The antigenicity of a protein is determined by its sequence of amino acids as well as by its conformation. Antigens may be introduced into an animal by ingestion, inhalation, sometimes by contact with skin, or more regularly by injection into the bloodstream, skin, peritoneum, or other body part.

With a few exceptions, such as the autoantigens and the isoantigens of the blood groups, antigens produce antibody only in species other than the ones from which they are derived. All complete proteins are antigenic, as are many bacterial and other polysaccharides, some nucleic acids, and some lipids. Antigenicity may be modified or abolished by chemical treatments, including degradation or enzymatic digestion; it may be notably increased by the incorporation of antigen into oils or other adjuvants. See Isoantigen

Bacteria, viruses, protozoans, and other microorganisms are important sources of antigens. These may be proteins or polysaccharides derived from the outer surfaces of the cell (capsular antigens), from the cell interior (the somatic or O antigens), or from the flagella (the flagellar or H antigens). Other antigens either are excreted by the cell or are released into the medium during cell death and disruption; these include many enzymes and toxins, of which diphtheria, tetanus, and botulinus toxins are important examples. The presence of antibody to one of these constituent antigens in human or animal sera is presumptive evidence of past or present contact with specific microorganisms, and this finds application in clinical diagnosis and epidemiological surveys. See Botulism, Diphtheria, Toxin

Microbial antigens prepared to induce protective antibodies are termed vaccines. They may consist of either attenuated living or killed whole cells, or extracts of these. Since whole microorganisms are complex structures, vaccines may contain 10 or more distinct antigens, of which generally not more than one or two engender a protective antibody. Examples of these are smallpox vaccine, a living attenuated virus; typhoid vaccine, killed bacterial cells; and diphtheria toxoid, detoxified culture fluid. Several independent vaccines may be mixed to give a combined vaccine, and thus reduce the number of injections necessary for immunization, but such mixing can result in a lesser response to each component of the mixture. See Vaccination

Allergens are antigens that induce allergic states in humans or animals. Examples are preparations from poison ivy, cottonseed, or horse dander, or simple chemicals such as formaldehyde or picryl chloride. See Hypersensitivity, Immunology

antigen

[′an·tə·jən]
(immunology)
A substance which reacts with the products of specific humoral or cellular immunity, even those induced by related heterologous immunogens.

antigen

a substance that stimulates the production of antibodies
References in periodicals archive ?
Identification of protective antigens for the control of Ixodes scapularis infestations using cDNA expression library immunization.
Immune responses to Bacillus anthracis protective antigen in patients with bioterrorism-related cutaneous or inhalational anthrax.
government for our recombinant protective antigen anthrax vaccine candidate; our plans to expand our manufacturing facilities and capabilities; the rate and degree of market acceptance and clinical utility of our products; the success of our ongoing and planned development programs, preclinical studies and clinical trials; the timing of and our ability to obtain and maintain regulatory approvals for our product candidates; our estimates regarding expenses, future revenue, capital requirements and needs for additional financing; and other factors identified in the company's Quarterly Report on Form 10-Q for the quarter ended June 30, 2010 and subsequent reports filed with the SEC.
rPA Anthrax Vaccine - a recombinant anthrax vaccine candidate, which is composed of a purified protective antigen protein adsorbed to an aluminum adjuvant and is designed to induce antibodies that neutralize anthrax toxins.
The Centers for Disease Control and Prevention developed, optimized, and rapidly qualified an enzyme-linked immunosorbent assay (ELISA) for immunoglobulin G (IgG) antibodies to Bacillus anthracis protective antigen (PA) in human serum.
In a presentation entitled, "Recombinant Protective Antigen Vaccine (SparVax[sup.
We sequenced the protective antigen gene (pagA) from 42 representative outbreak isolates and determined they all had a pagA sequence indistinguishable from the Ames strain (PA genotype I).
NYSE:EBS) announced today that the Department of Health and Human Services (HHS) has informed the company that its proposal to provide a recombinant protective antigen anthrax vaccine (rPA) is technically acceptable and within the competitive range.
About ETI-204 ETI-204 is a high-affinity, humanized and deimmunized monoclonal antibody that targets the Protective Antigen of B.
These toxins gain access to the cell through a third component known as protective antigen (PA), which binds to the cell surface receptor (6).
Department of Health and Human Services (HHS) for a recombinant protective antigen anthrax vaccine (rPA).
In a presentation entitled, "Factors that Affect Potency and Stability for a Recombinant Protective Antigen Vaccine," Dr.