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

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

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.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

antigen

a substance that stimulates the production of antibodies
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005
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Kilavuzlara Gore Kronik Hepatit B'de Antiviral Tedavi Kesilme Onerilerinin Ozeti Kilavuz HBeAg-Pozitif HBeAg-Negatif EASL 2017 (13) HBsAg klirensi (en HBsAg klirensi guvenlisi) Secilmis hastalarda HBeAg [greater than or serokonversiyonu ve equal to] 3 yil HBV DNA'nin tedaviyi virolojik baskilanma takiben 6-12 ay elde edilmisse ve NA saptanamaz halde kesilince en az bir olmasi yil takip guvencesi saglanmissa AASLD 2018 (14) HBsAg klirensi HBsAg klirensi Hasta temelinde degerlendirilmeli, riskler hastaya anlatilmali ve karar hastaya ve hekimine birakilmali APASL 2016 (15) HBeAg Anti-HBs serokonversiyonu serokonversiyonuyla beraberinde birlikte HBsAg tedavinin 1-3.
In HepG2.RL1 cells, NCC inhibited HBeAg expression almost as efficiently as adefovir, while inhibited intracellular DNA replication more efficiently than adefovir (0.84 [+ or -] 0.12 [micro]M versus 2.24 [+ or -] 0.11 [micro]M).
The [sup.G][1896.sup.A] mutation accounts for the HBeAg-negativity in non-A genotypes and this mutation introduces a stop-codon in the HBeAg precursor, which leads to its truncation and to the non-expression of the mature HBeAg.
The aims of antiviral treatment are suppression of HBV replication, permanent suppression of the viral load, seroconversion of HBeAg and HBV surface antigen (HB-sAg), normalization of aminotransferase levels, and a decrease in inflammation and fibrosis of the liver.
All HBsAg positive samples were retested for HBeAg using a commercial test strip, the INSIGHT HBeAg test (Tulip Diagnostics (P) Ltd, India).
Li et al., "High serum IL-21 levels after 12 weeks of antiviral therapy predict HBeAg seroconversion in chronic hepatitis B," Journal of Hepatology, vol.
Compared with nonsignificant fibrosis patients (F0-1), patients with significant liver fibrosis (F2-4) had lower HBV DNA, HBsAg, HBeAg, and platelet count levels and higher anti-HBc, alpha-fetoprotein (AFP), AST, globulin, GGT, laminin, IV-C, LSM, and spleen thickness (Supplementary Table 1).
Differential plasma microRNA profiles in HBeAg positive and HBeAg negative children with chronic hepatitis B.
Three factors were significantly associated with HBeAg status: an increased prevalence of anti-HBe (p = 0.004) and increased prevalence of precore G1896A (p = 0.003) and G1899A (p = 0.019) mutations.
The prevalence of HbeAg in chronic HBV was 28.2 % (males 16.10 %, females 12.08%) with more patients (22.14%) between 21 and 40 years of age.