antigen

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Related to HBeAg: anti-HBe, HBeAb, HBcAg

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 ?
Our study suggested that the activated pDC and the elevated IFN level could trigger the immune response against HBV in chronic hepatitis development from IT, and it might be the basis for those patients in immune active phase receiving PEG-IFN therapy to achieve a higher rate of HBeAg seroconversion and sustained response.
The seroconversion of HBeAg to anti-HBe in samples with active viral replication is directly related to the presence of mutations in HBV in the BCP region, especially the HBV A1762T/G1764A double mutation.
It has been observed that the pattern of decline in the HBeAg titers during antiviral therapy has profound effects on the clinical outcome and chances of viral breakthrough7.
HBeAg positivity was associated with HBV replication and with the occurrence of HBV resistance mutations.
15 cell proliferation by 50%; DEPT, distortionless enhancement by polarization transfer; DMEM, Dulbecco's modified Eagle's medium; DMSO, dimethyl sulfoxide; ELISA, enzyme-linked immunosorbent assay; HBeAg, hepatitis B e antigen; HBsAg, hepatitis B surface antigen; HBV, hepatitis B virus; HMBC, [sup.
The objective of present study was to determine the sero-prevalence of HBsAg, Anti HBs and HBeAg among married women of childbearing age in district Islamabad.
19), the rate of loss of HBeAg and HBVDNA was found to be 23% in the patients who were receiving lamivudine treatment (20).
The MTCT risk is related to the HBV deoxyribonucleic acid (DNA) status or HBeAg positivity of the mother, where a mother who is HBeAg positive has a 90% chance of transmitting this disease to her newborn but this figure drops to 20% if the mother is HBeAg negative.
La fase de portador inactivo se caracteriza por un perfil serologico HBeAg negativo y anti-HBe positivo, niveles bajos de ADN viral y minima fibrosis hepatica.
6,7 The goal of the treatment for hepatitis B virus-related cirrhosis patients is to suppress the replication of the virus, keep the HBeAg being negative and prevent the deterioration of liver function, therefore anti-hepatitis B virus treatment plays very important role in treating cirrhosis.
Seroconversion from HBeAg to e antibody (anti-HBe) is usually accompanied with cessation of HBV replication, remission of liver disease with a decrease in serum HBV viral load and is associated with a favourable prognosis (8,9).