An in vitro model for the allergen-IgE-Fc epsilon RI interaction

Background: The interaction of immune complexes consisting of allergens and allergen-specific IgE with the high-affinity Fc epsilon receptor represent s the key event in the induction of symptoms in type I allergic individuals . Immediate-type symptoms result from the release of biological mediators d ue to allergen-induced cross-linking of Fc epsilon RI receptors on mast cel ls and basophils, whereas Fc epsilon RI-mediated presentation of allergen-I gE complexes may contribute to late-phase symptoms through enhanced T cell activation. The interaction of allergens/allergen-specific IgE/Fc epsilon R I represents, therefore, an important target for therapeutic intervention s trategies in type I allergy. Methods and Results: A molecular model of the allergen-IgE-Fc epsilon RI interaction was established. It consists of reco mbinant purified Bet v 1, the major birch pollen allergen, a chimeric Bet v 1 specific monoclonal IgE antibody, and the baculovirus-expressed purified human alpha chain of FceRI. The chimeric Bet v 1-specific IgE antibody con sists of the light chain and the heavy chain variable region of a mouse mon oclonal Bet v 1 specific antibody, Bip 1, and the constant region of human IgE. The interaction of rBet v 1, chimeric Bip 1, and human alpha chain was investigated by overlay experiments. Nitrocellulose-immobilized recombinan t alpha chains was incubated with chimeric Bip 1 and, for control purposes, with mouse-derived Bip 1. Bound chimeric Bip 1 was detected with I-125-lab eled rBet v 1. The specific interaction of rBetv 1, chimeric Bip 1, and rec ombinant human alpha chain is demonstrated. We thus establish a molecular m odel of the allergen/IgE/alpha chain interaction. The usefulness of the des cribed in vitro system is exemplified by the identification of a mouse mono clonal antihuman IgE antibody which blocked the IgE-alpha chain interaction . Conclusions: The module system consisting of rBet v 1, chimeric Bip 1, an d recombinant alpha chain may be used for the identification of competitors of the allergic effector reaction by means of high throughput screening of compounds or by combinatorial chemistry.