| S antigen | Viral antigen that remains in solution after the particles of virus have been removed by means of centrifugation; in the case of the influenza viruses, it is the internal helical structure, free of the external envelope. Synonym: S antigen. (05 Mar 2000) |
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| proliferating cell nuclear antigen | Acidic nuclear protein (33 kD) highly expressed in dividing cells. Interacts with D type cyclins. (18 Nov 1997) |
| hepatitis-associated antigen | A term used for the surface antigen of hepatitis B virus before its nature was established. See: hepatitis B surface antigen. (05 Mar 2000) |
| hepatitis B antigen | Antigens of the virion of the hepatitis b virus or the dane particle, its surface, core and other associated antigens, like the hbe antigen. (12 Dec 1998) |
| hepatitis B core antigen | <virology> (HBcAb, HBcAg), the antigen found in the core of the Dane particle (which is the complete virus) and also in hepatocyte nuclei in hepatitis B infections. (05 Mar 2000) |
| hepatitis B e antigen | (HBeAb, HBe, HBeAg), an antigen, or group of antigen's, associated with hepatitis B infection and distinct from the surface antigen (HBsAg) and the core antigen (HBcAg); it is associated with the viral nucleocapsid. Its presence indicates that the virus is replicating and the individual is potentially infectious. (05 Mar 2000) |
| hepatitis B surface antigen | <virology> A serologic marker on the surface of the hepatitis B virus. The body will normally produce antibodies to hepatitis B surface antigen as part of the normal immune response to infection. It is the presence of antibodies to the hepatitis B surface antigen that are detected in a positive hepatitis B blood test. (27 Sep 1997) |
| prostate-specific antigen | <tumour marker> A simple blood test used to detect prostate cancer in men. The test measures a specific antigen normally secreted by the prostate. If cancer is developing, the prostate secretes greater amounts of prostate-specific antigen. This test is recommended for men with an enlarged prostate and an increased risk of prostate cancer. It is an enzyme that is produced by epithelial cells of both benign and malignant prostate tissue. It is an important marker for the diagnosis of prostate cancer. It is a single chain 31 kilodalton glycoprotein with 240 amino acid residues and 4 carbohydrate side chains that is a kallikrein protease. It is found in normal seminal fluid and produced by the prostatic epithelial cells. Elevated levels in blood serum are associated with prostatic enlargement and prostatic adenocarcinoma, and this allows early detection of cancer in many cases. In about 70% of cases, the rise is due to a cancerous condition. No large scale clinical studies have been completed to assess the impact of testing on survival from prostate cancer, and the medical and economic value of testing remain uncertain. Acronym: PSA Registry number: EC 3.4.21.77 (22 Sep 2002) |
| heterogeneic antigen | An antigen or antigenic determinant which is found in different tissues in more than one species. (05 Mar 2000) |
| heterogenetic antigen | An antigen which is possessed by a variety of different phylogenetically unrelated species; e.g., the various organ-or tissue-specific antigen's, the alpha-and beta-crystalline protein of the lens of the eye, and Forssman antigen. Synonym: heterophil antigen. (05 Mar 2000) |
| heterogenic enterobacterial antigen | Cross reacting antigen (epitope), a common antigen that occurs in 2 or more different molecules/organisms. Synonym: heterogenic enterobacterial antigen. (05 Mar 2000) |
| heterophil antigen | An antigen which is possessed by a variety of different phylogenetically unrelated species; e.g., the various organ-or tissue-specific antigen's, the alpha-and beta-crystalline protein of the lens of the eye, and Forssman antigen. Synonym: heterophil antigen. (05 Mar 2000) |
| heterophile antigen | An antigen or antigenic determinant which is found in different tissues in more than one species. (05 Mar 2000) |
| Xg antigen | xg blood group |
| histocompatibility antigen | <immunology> A set of plasmalemmal glycoproteins on the surface of all nucleated cells that are crucial for T-cell recognition of antigens. Particularly the HLA system in humans and the H2 system in mice. They are the major antigens responsible for tissue recognition. For this reason, they are of prime importance in determining compatible organ donors for a specific transplantation procedure. Each person has unique HLA antigens. Some HLA antigens have been identified to be correlated with the presence of certain autoimmune diseases. One of these is the HLA-B27 site. Approximately 85% of patients with ankylosing spondylitis and Reiter's syndrome will have the HLA-B27 antigen present on the leukocytes. There are two classes of histocompatibility antigens: 1. Class I, histocompatibility antigens composed of two glycosylated subunits, a heavy chain of 44 kD and beta2 microglobulin (12 kD). The heavy chain may be coded by K, D or L genes of mouse H2 and A, B or C genes of human HLA complex. Class I antigens are important in T-cell killing and are recognised in conjunction with the foreign cell surface antigens MHC restriction). 2. Class II antigens, heterodimeric histocompatibility antigens composed of alpha (32 kD) and beta (28 kD) chains. Found mostly on B lymphocytes, macrophages and accessory cells. The response of T helper cells requires that the foreign antigen is presented in conjunction with the appropriate Class II antigens. (Murine H2 Ia antigens and human HLA DR antigens are Class II). (14 Oct 1997) |