delayed hypersensitivity(redirected from tuberculin-type hypersensitivity)
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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.
1. Synonym(s): cell-mediated immunity
2. Synonym(s): delayed reaction
3. a cell-mediated response that occurs in immune people peaking at 24-48 hours after challenge with the same antigen used in an initial challenge. The interaction of T-helper 1 (Th-1) lymphocytes with MHC class II positive antigen-presenting cells initiates the response. This interaction induces the Th-1s and macrophages at the site to secrete cytokines, which are the major factors in the reaction. Called tuberculin-type hypersensitivity.
Farlex Partner Medical Dictionary © Farlex 2012
delayed hypersensitivityAn allergic reaction occurring two to three days after the antigen contact and mediated by CYTOKINE release from sensitized T cells (T LYMPHOCYTES).
Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005
de·layed hy·per·sen·si·ti·vi·ty(dē-lād hīpĕr-sensi-tivi-tē)
A cell-mediated response that occurs in immune people peaking at 24-48 hours after challenge with the same antigen used in an initial challenge.
Medical Dictionary for the Dental Professions © Farlex 2012