The Stripped Basophil Histamine Release Bioassay as a Tool for the Detection of Allergen-Specific IgE in Serum

Background: For the detection of allergen-specific IgE in serum, IgE-binding assays such as the radioallergosorbent assay (RAST) are commonly used. In this study, the applicability and sensitivity of the stripped basophil histamine release bioassay was investigated and compared to the RAST. Methods: Basophils were stripped of their IgE by an acidic buffer, sensitized by human serum and stimulated by allergen with or without interleukin (IL)-3. The histamine release was determined by fluorometric analysis. Results: We showed that for enhancement of the maximal histamine release and the sensitivity of the stripped basophil assay, the priming cytokine IL-3 can be added to the basophils simultaneously to the stimulus. Preincubation of the cells with IL-3, as described in other studies, was not necessary. The bioassay can be used to study the specificity of IgE-mediated reactions. Basophils sensitized by serum absorbed to a particular allergen did not respond to this allergen anymore. This method is very suitable to study cross-reactivity between allergens. The results obtained in the bioassay were comparable to those obtained in the RAST. Using the RAST, lower concentrations of allergen-specific IgE were detected than in the bioassay. However, sera containing IgE against minor allergenic components were negative in the RAST, but strongly positive in the basophil assay. Conclusions: The stripped basophil histamine release bioassay is useful to complement and extend serological detection of allergen-specific IgE. Especially with sera containing IgE against minor components, this assay is more suitable than the RAST. Furthermore, in this assay, the dependency of IgE and of allergen-specific IgE in reactions can be studied in more detail.