reagin-mediated disorder

reagin-mediated disorder,

a hypersensitivity reaction, such as hay fever or an allergic response to an insect sting, produced by reaginic (immunoglobulin E [IgE]) antibodies and causing degranulation and the release of histamine, bradykinin, serotonin, and other vasoactive amines. An initial sensitizing dose of the antigen induces the formation of specific IgE antibodies, and their attachment to mast cells and basophils results in hypersensitivity to a subsequent challenging dose of the antigen. Reactions range from a simple wheal and flare on the skin to life-threatening anaphylactic shock, depending on the size and route of entrance of the sensitizing dose and the challenging dose, the number and distribution of IgE antibodies, the responsiveness of the host, the timing of exposure to the allergen, and the tissues in which the antigen-antibody reaction occurs. The abundance of mast cells in the skin, nose, and lungs makes these areas susceptible to IgE-mediated reactions. Allergens that commonly cause these reactions include plant spores, pollens, animal danders, stings, serum proteins, foods, and certain drugs. See also allergy, anaphylactic shock, hay fever.