The atopic dog: a model for food allergy.

The renewed interest in food allergy and its investigation has been hampered by the lack of an appropriate animal model with similar comparative aspects of form and function relative to humans. Therefore we have been characterizing an inbred colony of high immunoglobulin E-producing dogs that were immunized subcutaneously with food antigen extracts in alum and that developed clinical manifestations of food allergy after oral challenges with food antigen. These dogs had appreciably high IgE antibody titer to specific food antigens, as measured by an enzyme-labeled immunodot assay. Skin test results for the food antigens were consistently positive, as evidenced by a wheal-and-flare reaction. Gastroscopic food sensitivity was tested through an endoscope by injecting allergenic food extracts into the gastric mucosa after intravenous injection of Evans blue dye. Mucosal changes included swelling and erythema, some petechiae and blue patching, and in some instances generalized gastric erythema and hyperperistalsis. Examination of immediate-reaction biopsy specimens revealed edema and few inflammatory cells. Examination of late-reaction biopsy specimens revealed increased eosinophil and mononuclear cell infiltrations typical of late-phase allergic inflammatory responses. Direct mucosal challenge with food extracts confirmed the clinical and immunologic evidence of food allergy in these immunized dogs and suggests the usefulness of the atopic dog as a model for food allergy. This model might also be useful in detecting hidden food allergies in unexplained inflammatory gastrointestinal tract diseases.