Immunoblot studies in birch pollen-allergic patients with and without fruit hypersensitivity: part I: antibody...

About 40-70% of birch pollen allergic patients show allergic symptoms after ingesting or handling raw fruits. Several investigations have indicated a partial immunological identity between birch pollen and stone fruit. To further clarify this association, we investigated 59 patients with allergic symptoms (conjunctivitis, rhinitis, and asthma during the birch pollen season) and 18 nonatopic controls by skin prick test (SPT) and RAST with birch pollen, fresh apple, cherry, and peach as well as freshly prepared fruit extracts. According to a questionnaire dealing with symptoms after ingestion of raw fruits, the subjects were divided into groups with (35 FH+) and without (24 FH-) fruit hypersensitivity. IgE, IgG, IgG1, IgG4, IgA, and IgM binding patterns to birch pollen extracts were performed with 33 sera (12 FH+, 11 FH-, and 10 nonatopic controls) using the immunoblot-technique. Patients with FH+ expressed a significantly stronger sensitization to birch pollen than patients without FH-, as measured by RAST and SPT. Native fruits induced stronger SPT reactions than fruit extracts, and patients with FH+ showed a significantly higher skin index with all fruits and fruit extracts tested. Specific IgE, IgG, IgG1, IgG4, IgM and IgA to birch pollen extracts could be detected by immunoblot in all groups, albeit with different frequencies and intensities. From this data we conclude that fruit hypersensitivity is related more to the 17 kd and 67-85 kd than to the 26-28 kd or 36 kd protein bands of the birch pollen extract. The relationship of specific IgE > IgG > IgM to a single protein band seems to be associated with the development of symptomatic type I allergy.