IgE and IgG antibodies of patients with allergy to birch pollen as tools to define the allergen profile of Betula verrucosa*

IgE and IgG antibody response to birch pollen antigens were studied by means of immunoblotting experiments testing 58 sera from patients with Type I allergy to birch pollen. 56/58 patients showed IgE antibodies reactive with Bet v I, a 17 kilodalton (kD) pollen protein. 2D-electrophoresis/immunoblot revealed a heterogeneity of that protein. Ten spots (pH 4.9-5.9) could be detected, presumably representing differentially glycosylated isoallergens. In 33/58 patients, there was no evidence of IgE antibodies directed against allergens other than Bet v I. However, in 25/58 of patients' sera, 11 minor allergens (13, 15, 18, 27, 29, 32, 39, 44, 57, and 68 kD) with individual incidences from 1.7% to 17.2% were identified. All proteins were also recognized by the patients' IgG antibodies: in the case of Bet v I recognition was weak, whereas the IgG response to the minor allergens was pronounced. Sera from healthy individuals showed similar IgG antibody responses, but no IgG to the 15, 27, and 29 kD proteins. Our results suggest that IgG directed against minor allergens may function as trapping antibodies in healthy individuals. Too low or lacking amounts of anti-Bet v I IgG may facilitate an allergic reaction.