immediate hypersensitivity

hypersensitivity

 [hi″per-sen″sĭ-tiv´ĭ-te]

a state of altered reactivity in which the body reacts with an exaggerated immune response to a foreign agent; anaphylaxis and allergy are forms of hypersensitivity. The hypersensitivity states and resulting hypersensitivity reactions are usually subclassified by the Gell and Coombs classification. adj., adj hypersen´sitive.

contact hypersensitivity that produced by contact of the skin with a chemical substance having the properties of an antigen or hapten.

delayed hypersensitivity (DH) (delayed type hypersensitivity (DTH)) the type of hypersensitivity exemplified by the tuberculin reaction, which (as opposed to immediate hypersensitivity) takes 12 to 48 hours to develop and which can be transferred by lymphocytes but not by serum. Delayed hypersensitivity can be induced by most viral infections, many bacterial infections, all mycotic infections, and a few protozoal infections (leishmaniasis and toxoplasmosis). The scope of the term is sometimes expanded to cover all aspects of cell-mediated immunity including contact dermatitis, granulomatous reactions, and allograft rejection.

immediate hypersensitivity antibody-mediated hypersensitivity occurring within minutes when a sensitized individual is exposed to antigen; clinical manifestations include systemic anaphylaxis and atopic allergy (allergic rhinitis, asthma, dermatitis, urticaria, and angioedema). The first exposure to the antigen induces the production of IgE antibodies (cytotropic antibodies, reagin) that bind to receptors on mast cells and basophils. Subsequent exposure to the antigen triggers production and release of a diverse array of mediators of hypersensitivity that act on other cells producing symptoms such as bronchospasm, edema, mucous secretion, and inflammation.

hypersensitivity reaction the exaggerated or inappropriate immune response occurring in hypersensitivity, in response to a substance either foreign or perceived as foreign and resulting in local or general tissue damage. Such reactions are usually classified as types I–IV on the basis of the Gell and Coombs classification.

Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.

im·me·di·ate hy·per·sen·si·tiv·i·ty

an exaggerated immune response mediated by mast cell-bound IgE antibodies occurring within minutes after exposing a sensitized individual to the approximate antigen; also called Type I hypersensitivity. Clinical symptoms result from the physiologic effects of preformed or newly generated mediators, including histamine, platelet activating factor, prostaglandins, leukotrienes, bradykinin, tachykinins, and others. The reaction may be localized to specific organ systems or be generalized, leading to anaphylaxis. Symptoms include pruritus, urticaria, angioedema, conjunctivitis, sneezing, rhinorrhea, bronchospasm, hypotension, arrhythmias, and shock. See: allergy.

Synonym(s): immediate allergy, immediate hypersensitivity reaction

Farlex Partner Medical Dictionary © Farlex 2012

immediate hypersensitivity

Immediate hypersensitivity reaction Immunology An event unleashed by cross-linking of IgE antibodies on the surfaces of mast cells and basophils, after exposure to an allergen to which a person has been previously sensitized, resulting in release of histamine and related compounds

McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.

im·me·di·ate hy·per·sen·si·tiv·i·ty

(i-mēdē-ăt hīpĕr-sen-si-tivi-tē)

Exaggerated immune response mediated by mast cell-bound immunoglobulin E antibodies occurring within minutes after exposing a sensitized individual to the approximate antigen; also called Type I hypersensitivity.

Medical Dictionary for the Health Professions and Nursing © Farlex 2012

im·me·di·ate hy·per·sen·si·tiv·i·ty

(i-mēdē-ăt hīpĕr-sen-si-tivi-tē)

An exaggerated immune response mediated by mast cell-bound IgE antibodies occurring within minutes after exposing a sensitized patient to the approximate antigen; also called Type I hypersensitivity.

Medical Dictionary for the Dental Professions © Farlex 2012