The immunological relationship of epitopes on major tree pollen allergens

The major allergens of birch ( Bet v I), alder ( Aln g I), hazel ( Cor a I) and hornbeam ( Car b I) were investigated by means of high-resolution two-dimensional electrophoresis combined with immunoblotting. Eleven sera derived from patients allergic to birch pollen as well as mouse monoclonal antibodies BIP 1 and BIP 4, raised against Bet v I, were used as probes. Human IgE antibodies detected 10 spots in birch (M r 17 kDa, p I4.9–5.9); four spots in alder (M r 18.5 kDa, p I4.7–5.3); four spots in hazel (M r 17 kDa, p I 5.0–5.8); and 12 + 7 spots in hornbeam (M r 16.5 kDa, p I 4.9–6.6 and M r 18 kDa, p I 5.2–6.7), respectively, representing major allergens. Each patient tested reacted in a similar fashion with the spot eluster(s) of a certain allergen. BIP 1 detected the same spot clusters as patients' IgE. BIP 4 reacted with the 17-, 18.5- and 18-kDa spots of birch, alder and hornbeam, but did not react with the 17-kDa spots of hazel and the 16.5-kDa spots of hornbeam. In inhibition experiments with birch pollen extract as inhibitor, IgE binding to Bet v I, as well as to Aln g I, Cor a I and Car b I was abolished, thus suggesting that IgE binding to major tree pollen allergens is confined to shared epitopes. These findings indicate that it might be sufficient to use only Bet v I for diagnostic procedures as well as for immunotherapy in patients with tree pollen allergy.