IgE immune response to Ginko biloba pollen

Background: The ginkgo (Ginkgo biloba L.) continues to be planted as a shade tree in preference to other species in Seoul, Korea. The proportion of ginkgo to total shade trees was 43.2% in 1998, but the allergenic characteristics of ginkgo pollen has not been elucidated. Objectives: This study was undertaken to obtain information regarding the skin reactivity rate to ginkgo pollen in a population of Korean subjects with respiratory allergy. Possible ginkgo pollen allergens and the cross-reactivity of ginkgo pollen with other prevalent pollens were also examined. Methods: Four hundred and forty-seven patients with asthma and/or allergic rhinitis were skin prick tested with extract of ginkgo pollen (1:20 wt/vol). Of these patients, positive skin responders (A/H ratio ≥2+) were selected for ELISA and immunoblot experiments. Results: A total of 21 patients (4.7%) showed skin reactivity (A/H ratio ≥2+) to ginkgo pollen in the skin prick test. They were also cosensitized to many other tree, grass, and weed pollens. Sixteen (76%) of the 21 positive skin responders showed specific IgE responses to ginkgo pollen in ELISA. In inhibitory ELISA, IgE binding to ginkgo pollen was inhibited by more than 80% by oak, ryegrass, mugwort, and ragweed; and 34% by hop Japanese; and 10% by rBet v 2 at 10 μg/mL. In immunoblot, 10 out of 21 sera (48%) reacted to the 15-kD protein of ginkgo pollen, 9 (43%) to 33-35 kD, and 8 (38%) to 36-38 kD. In inhibitory immunoblot, IgE binding to ginkgo pollen proteins was almost completely inhibited by oak, ryegrass, mugwort and ragweed, but only partially by hop Japanese and rBet v 2. Conclusion: The skin reactivity rate to ginkgo pollen is approximately 4.7% in a population of Korean subjects with respiratory allergy. Since ginkgo pollen has a high cross-reactivity with other prevalent pollens, it could cause clinical symptoms during its pollen season by cross-reacting with the IgE produced in response to other pollens in patients sensitized to multiple pollens.