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, anaphylaxis was used by Arthus to indicate an induced sensitivity; at times anaphylaxis 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 anaphylaxis. Syn: anaphylactic reaction.
[G. ana, away from, back from, + phylaxis, protection]
passive cutaneous anaphylaxis
reversed passive anaphylaxis