Characterization of IgE cross-reactivity and allergenicity of peanut allergens.

IgE cross-reactivity among peanut allergens is controversial, and allergenicity of peanut allergens other than Arachis hypogaea 2 [Ara h 2] remains to be elucidated. We investigated the origins of peanut IgE cross-reactivity using Western blotting, and allergenicity of peanut allergens employing a passive cutaneous anaphylaxis model. Peanut allergic IgE bound to a large swath of peanut proteins including Ara h 2, Ara h 1, Ara h 3, and Ara h 6. IgE cross-reactivity among peanut allergens could be inhibited by recombinant Ara h 2. Affinity-purified Ara h 2 IgE reconstituted broad IgE binding patterns to Ara h 1, Ara h 3, and Ara h 6 in addition to Ara h 2. Monoclonal human IgE and mouse IgG against peanut allergen component variably bound to other peanut allergen components. Ara h 2 and Ara h 6 could trigger Ara h 2 IgE-mediated peanut allergic reactivity, whereas Ara h 1 and Ara h 3 failed to do so. Ara h 1 IgE was incapable of mediating Ara h 1-triggered allergic reaction. These results revealed that Ara h 2 IgE was the origin of IgE cross-reactivity, and Ara h 2 IgE-mediated peanut allergic reactivity triggered by Ara h 2 and Ara h 6. Ara h 1 and Ara h 3 did not display detectable allergenicity. These results indicated that Ara h 2 IgE appeared to be the "master" responsible for IgE cross-reactivity among peanut allergens and might be the only IgE responsible for allergic reactivity in peanut allergy.