MOLECULAR CHARACTERIZATION OF BIP-1, A MONOCLONAL-ANTIBODY THAT MODULATES IGE BINDING TO BIRCH POLLEN ALLERGEN, BET-V-1

Bet v 1 and homologous proteins represent major cross-reactive allerge ns for more than 95% of tree pollen-, fruit-, and vegetable-allergic i ndividuals. To study the interaction of Bet v 1 and the immune system, we characterized a Bet v 1-specific mAb, Bip 1, Soluble rBip 1 Fabs w ere expressed in Escherichia coli and purified by affinity chromatogra phy using immobilized Bet v 1. Bip 1 Fabs displayed a cross-reactivity to homologous allergens comparable with that of IgE Abs from allergic patients. Preincubation of Bet v 1 with Bip 1 led to an up to fivefol d increase of allergic patients' IgE binding to Bet v 1, This enhancem ent in IgE binding may be interpreted as stabilization of a Bet v 1 st ate, in which certain IgE epitopes are better applicable. It also show s that allergic patients possess IgE Abs directed against different Be t v 1 conformations. The modulation of Ab binding to a given Ag by oth er Abs was observed also for human Bet v 1-specific IgG Abs, and may r epresent a novel mechanism for the regulation of specific humoral immu ne responses in a complex network.