Measurement of canine IgE using the alpha chain of the human high affinity IgE receptor

In vitro assays for allergen specific immunoglobulin E (IgE) are a convenient and reproducible alternative to intradermal skin testing in dogs. Such tests may be used to support a diagnosis of atopic dermatitis and to define appropriate allergens for immunotherapy. Current in vitro assays rely upon monoclonal or polyclonal antibodies as IgE detection reagents. However, in sera where allergen-specific IgG occurs in great excess, any IgE:IgG cross-reactivity of the detection reagent may result in lowered assay specificity. Therefore, we have developed an assay for canine IgE which uses a recombinant form of the extracellular part of the alpha chain of the human high affinity IgE receptor (FcεRIα). Biotinylated FcεRIα shows no significant binding to purified canine IgG, and recognizes a heat labile antibody in serum, with a detection limit of 73–146 pg/ml. Comparison of assay signals using the labeled FcεRIα and a highly specific anti-canine IgE monoclonal antibody (MAb) shows good agreement. The FcεRIα is therefore a sensitive and specific alternative to polyclonal or monoclonal antibodies for canine serum IgE measurement.