Delayed Anaphylaxis and Urticaria Associated with Eating Mammalian Meat: Are IgE Antibodies to a Common Carbohydrate Capable of Mediating Systemic Reactions?

Abstract

RATIONALE: We have identified 20 patients with similar histories of anaphylaxis or urticaria 3-6 hours after the ingestion of beef, pork or lamb who have IgE ab to galactose-alpha-1,3-galactose (alpha-gal). Given the diagnostic challenges posed by delayed reactions, we performed in vivo (skin testing) and in vitro (basophil activation) studies to investigate these reactions. METHODS: Detailed histories were taken from adult patients presenting to the Allergy Clinic at the University of Virginia with recurrent anaphylaxis or urticaria. Skin prick tests (SPT), intradermal tests (ID) and basophil activation were performed. RESULTS: These patients had <4 mm reactions on SPT to mammalian meat using conventional extracts, whereas intradermal or fresh food SPT provided larger, more consistent wheal responses. Interestingly, inhibition-radioimmunoassays using alpha-gal showed increased levels of alpha-gal in fresh extracts of beef, pork and lamb used for SPT compared to commercial reagents. Patients did not report symptoms after eating fish, turkey or chicken and had negative SPT to these foods. Inhibition-radioimmunoassays of extracts (commercial and fresh) of fish, turkey or chicken were negative for alpha-gal. Moreover, blood from patients with IgE ab to alpha-gal had increased expression of CD203c on the surface of basophils in response to alpha-gal and beef thyroglobulin compared to that of controls. CONCLUSIONS: In vivo testing of patients with IgE ab to alpha-gal indicated that SPT using fresh extracts of mammalian meat was superior to commercial reagents and is likely explained by the increased presence of alpha-gal, while in vitro studies showed that IgE ab to this carbohydrate can produce basophil activation.