High-dose allergen exposure leads to tolerance |
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Authors: | Judith A Woodfolk |
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Institution: | (1) Asthma and Allergic Diseases Center, University of Virginia Health System, Charlottesville, VA |
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Abstract: | Reports of decreased sensitization to cat allergen (Fel d 1) among individuals living with a cat or subjects exposed to high-dose
cat allergen may be explained by the development of a form of high-dose tolerance resulting from natural exposure to an inhalant
allergen. Although the epidemiological data regarding the relationship between exposure and sensitization to Fel d 1 are conflicting,
the ability for high-dose Fel d 1 to induce a characteristic nonallergic immune response with a distinctive serum antibody
profile has been established. Definition of this modified T-helper (Th)2 response to cat allergen, coupled with the renewed
interest in regulatory T cells within the immunology field, has provided an avenue for exploring the mechanism by which IgE
antibody-mediated responses are controlled. There is mounting evidence to suggest that the modified Th2 response is a variation
of the allergic response and that the modified Th2-allergic axis is influenced by allergen dose and genetics. This article
discusses putative immune mechanisms of tolerance within the context of an allergen-specific system. The relevance of high-dose
allergen exposure and alternate factors such as endotoxin to the development of tolerance is considered. Fel d 1 exhibits
unique molecular and immunological characteristics that may contribute to its tolerogenic properties. Major T-cell epitopes
of Fel d 1 that preferentially induce regulatory factors have been defined. Furthermore, hightiter IgE antibody responses
associated with atopic dermatitis are characterized by a defect in the T-cell repertoire that is specific to these epitopes.
Identification of Fel d 1 epitopes that induce interleukin-10 may provide new targets for treatment. |
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Keywords: | Cat allergen regulatory T cell interleukin-10 T helper 1 T helper 2 tolerance |
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