antigen
(ˈæntɪdʒɛn)
[a. G. antigen, ad. F. antigène adj. (L. Deutsch 1899, in Ann. de l'Inst. Pasteur XIII. 704), f. antibody + -gen.]
A foreign substance which, when introduced into a living organism, stimulates the production of an antibody.
| 1908 Park & Bolduan in Nuttall & Graham-Smith Bacteriol. of Diphtheria 628, v. Pirquet and Schick attribute the immediate or hastened reaction and indeed the serum disease as a whole to an interaction between the antigen and the antibody. 1911 Jrnl. Chem. Soc. C. ii. 812 When an optimum dose of antigen (goat's or rat's blood) is injected intravenously into a dog. 1955 Sci. News Let. 16 Apr. 253/1 The test reaction is based on the body's ability to react to and destroy bacteria and foreign protein invaders. These foreign agents are called antigens, while the body's own destructive agents are referred to as antibodies. 1959 Chambers's Encycl. VII. 398/1 Most antigens are proteins or contain substantial amounts of protein, and they have a high molecular weight. |
Hence antiˈgenic a., of the nature of an antigen, antiˈgenically adv. So ˌantigeˈnicity, the condition or property of being antigenic.
| 1913 Arch. Internal Med. XI. 85 The ‘antigenic’ function of all the extracts resides solely in the lipoid fraction. 1916 Olitsky & Bernstein in Jrnl. Infectious Diseases XIX. 259 We have shown that organisms grown on serum media incorporate..those serum elements which possess serum antigenic properties. 1946 Nature 27 July 120/1 The hæmagglutinins are complexes of a phospholipid (probably lecithin) with an antigenically specific virus constituent. Ibid. 17 Aug. 239/1 The loss in antigenicity during preparation of the toxoid (measured by flocculation) was about half that usually found. |
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▸ antigen-presenting cell n. Immunol. any cell that assists in the production of immune responses by presenting antigen (see present v.); esp. any of several types of cell with monocytic lineage that present antigen in association with class II MHC molecules, to helper T lymphocytes.
| 1975 Proc. National Acad. Sci. U.S.A. 72 5098/2 It may therefore be that..interaction between sensitized lymphocytes and *antigen-presenting cells leads to the generation of suppressive influences which prevent the DTH response. 1985 Sci. Amer. June 40/1 They set out to show that Langerhans cells synthesize interleukin-1 (IL-1), a factor known to be secreted by other antigen-presenting cells, the macrophages. 2000 Brit. Med. Jrnl. (Electronic ed.) 9 Dec. 1430 [Statins] do this by blocking the ability of interferon gamma, a cytokine, which activates antigen presenting cells, to express MHC-II on their surface. |