Immunologic significance of respirable atmospheric starch granules containing major birch allergen Bet v 1

Background: Birch‐pollen allergens are an important cause of early spring hay fever and allergic asthma. Recently, we reported a mechanism for the release of respirable allergenic particles from birch pollen containing the major allergen Bet v 1. In this study, we aimed to assess the immunologic significance of the released Bet v 1‐containing starch granules in the environment. Methods: A two‐site monoclonal antibody‐based assay (ELISA) was employed to quantitate Bet v 1 in high‐volume air sampler filter extracts, and immunogold‐labelling was used on sections of these extracts to localize Bet v 1. Immunoblot analyses were performed with pooled sera from patients sensitive to birch pollen. Results: Atmospheric starch granules contained Bet v 1, and the concentration increased upon light rainfall. Sera from patients allergic to birch allergens recognized extracts from isolated starch granules. Conclusions: The clinical implications of these findings are that starch granules released from birch pollen are potentially able to trigger allergic asthmatic reactions to Bet v 1, since the allergen occurs in respirable particles. Thus, clinicians can advise asthma patients to remain indoors on days of light rainfall during the birch‐pollen season to avoid high levels of allergen exposure.