Context matters: TH2 polarization resulting from pollen composition and not from protein-intrinsic allergenicity

Birch (Betula verrucosa) pollen is the main cause of spring pollinosis in the temperate climate zone of the Northern Hemisphere. Approximately 95% of birch pollen–allergic patients are sensitized to Bet v 1, the major birch pollen allergen.1 However, it is not known whether sensitization toward Bet v 1 results from its own intrinsic properties or from immunomodulatory pollen compounds codelivered with the allergen. Therefore, we investigated whether Bet v 1 or the pollen matrix is responsible for the activation of antigen-presenting cells and the subsequent TH2 polarization, relevant in the process of allergic sensitization.