immunity defined in 1951 yearimmunity - immunity;
immunity - Ability of an animal or plant to resist infection by parasitic organisms. An essential requirement for survival, since most animals and plants are perpetually menaced by viruses, bacteria, fungi, and parasitic animals. Immunity of animals is due to many different mechanisms, such as impervious skin, antiseptic stomach (due to acid), activity of phagocytes, and chemical defence by antibodies or interferon. The terms immunity and immune and the subject matter of the science of immunology are usually restricted to the particular kind of reaction induced in vertebrates by the introduction into the body of certain foreign substances (antigens) which include, but are not confined to, parasites. An immune reaction in this sense involves the production of substances which combine specifically with the particular antigen introduced. These specific substances may be antibodies in the body fluids, or they may be carried by blood cells (lymphocytes). An animal that is protected by antibodies is said to be immunized. Active immunity is such immunity induced in an animal by an antigen. Passive immunity is such immunity conferred by the transfer to an animal of antibodies that have been induced in another animal. Immunity in plants is (a) due to structural features, e.g. waxy surface preventing wetting and consequently development of pathogens, thick cuticle preventing entry of germ-tubes of fungus spores; or is (b) protoplasmic, the protoplast being an unfavourable medium for further development of a pathogen, See also: Phytoalexins; or is (c) acquired immunity, used with respect to virus diseases and applied to (1) recovery from an acute disease, and (2) resistance conferred against virulent strains by presence of avirulent ones, (c) is a non-sterile type of immunity which depends on persistence of active virus in the recovered or protected plants. Freedom from a second attack of an acute disease, or protection from the effects of virulent strains, persists only as long as the plants are infected. Plants are not known to produce antibodies.
near immunity in Knolik
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