Generating allergen-specific human IgEs for immunoassays by employing human ε gene knockin mice.

Background: Antigen-specific human IgEs are important reagents in immunoassays to quantify antigen-specific IgEs in allergic patients, but they are not easy to prepare. Methods: We constructed a knockin homozygous mouse strain, referred to as H epsilon kappa KI strain, whose gene segment encoding gamma 1 constant region has been replaced by that encoding human a constant region and gene segment encoding kappa constant region replaced by that encoding human kappa constant region. The mice were tested for their ability to produce antigen-specific chimeric human IgE (with mouse variable regions) upon the. immunization with ovalbumin and papain. Subsequently, the spleen cells from the immunized mice were used as the source of B cells for the preparation of hybridomas, which secreted monoclonal human IgE antibodies specific for the antigens. Results: The H epsilon kappa KI mice expressed human IgE (epsilon, kappa) in serum at levels 10- to 30-fold higher than those of mouse IgE. Upon immunization with an antigen, the mice yielded splenic B cells for preparing hybridomas that secrete chimeric human IgE specific for the antigen. Purified IgEs from those hybridomas could activate a basophilic cell line to undergo degranulation upon the stimulation with their respective antigens. Conclusions: We have developed a human epsilon gene and kappa gene knockin mouse strain, which is useful for producing various antigen-specific chimeric human IgEs for potential use as standards in immunoassays.