A term coined by Portier and Richet to indicate a lessened resistance to a toxin which results from a previous inoculation of the same material, and in this sense was synonymous with hypersensitivity in its original usage of a postulated increased sensitivity to a toxin; shortly thereafter, a. was used by Arthus to indicate an induced sensitivity; at times a. is used for anaphylactic shock. The term is commonly used to denote the immediate, transient kind of immunologic (allergic) reaction characterized by contraction of smooth muscle and dilation of capillaries due to release of pharmacologically active substances (histamine, bradykinin, serotonin, and slow-reacting substance), classically initiated by the combination of antigen (allergen) with mast cell-fixed, cytophilic antibody (chiefly IgE); the reaction can be initiated, also, by relatively large quantities of serum aggregates (antigen-antibody complexes, and others) that seemingly activate complement leading to production of anaphylatoxin, a reaction sometimes termed "aggregate a."anaphylactic reaction; [G. ana, away from, back from, + phylaxis, protection]
active a. reaction following inoculation of antigen in a subject previously sensitized to the specific antigen, in contrast to passive a.
aggregate a. See anaphylaxis.
antiserum a. passive a
chronic a. enteritis anaphylactica
generalized a. the immediate response, involving smooth muscles and capillaries throughout the body of a sensitized individual, that follows intravenous (and occasionally intracutaneous) injection of antigen (allergen). See also anaphylactic shock.systemic a;
inverse a. anaphylactic shock in an animal (e.g., guinea pig) whose tissues contain Forssman antigen, resulting from an intravenous injection of serum that contains Forssman's antibody.
local a. the immediate, transient kind of response that follows the injection of antigen (allergen) into the skin of a sensitized individual and is limited to the area surrounding the site of inoculation. See also skin test.
passive a. a reaction resulting from inoculation of antigen in an animal previously inoculated intravenously with specific antiserum from another animal, a latent period being required between the two inoculations.antiserum a;
passive cutaneous a. (PCA) a reaction that occurs in the guinea pig when antiserum is injected into the skin and, 6 to 24 hours later, specific antigen and a dye such as Pontamine blue or Evans blue are inoculated intravenously; the size of the blue areas at the sites of the antibody injections is a measure of the degree of altered permeability to dye-bound albumin.
reversed a. reversed passive a
reversed passive a. an anaphylactic reaction induced in an animal injected with a specific antigen, which will bind to reactive tissue, and then, after a latent period, with serum from another animal previously sensitized to the identical antigen.reversed a;
systemic a. generalized a
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