High environmental ozone levels lead to enhanced allergenicity of birch pollen

PLoS One. 2013 Nov 20;8(11):e80147. doi: 10.1371/journal.pone.0080147. eCollection 2013.


Background: Evidence is compelling for a positive correlation between climate change, urbanisation and prevalence of allergic sensitisation and diseases. The reason for this association is not clear to date. Some data point to a pro-allergenic effect of anthropogenic factors on susceptible individuals.

Objectives: To evaluate the impact of urbanisation and climate change on pollen allergenicity.

Methods: Catkins were sampled from birch trees from different sites across the greater area of Munich, pollen were isolated and an urbanisation index, NO2 and ozone exposure were determined. To estimate pollen allergenicity, allergen content and pollen-associated lipid mediators were measured in aqueous pollen extracts. Immune stimulatory and modulatory capacity of pollen was assessed by neutrophil migration assays and the potential of pollen to inhibit dendritic cell interleukin-12 response. In vivo allergenicity was assessed by skin prick tests.

Results: The study revealed ozone as a prominent environmental factor influencing the allergenicity of birch pollen. Enhanced allergenicity, as assessed in skin prick tests, was mirrored by enhanced allergen content. Beyond that, ozone induced changes in lipid composition and chemotactic and immune modulatory potential of the pollen. Higher ozone-exposed pollen was characterised by less immune modulatory but higher immune stimulatory potential.

Conclusion: It is likely that future climate change along with increasing urbanisation will lead to rising ozone concentrations in the next decades. Our study indicates that ozone is a crucial factor leading to clinically relevant enhanced allergenicity of birch pollen. Thus, with increasing temperatures and increasing ozone levels, also symptoms of pollen allergic patients may increase further.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Air Pollutants / analysis*
  • Allergens / immunology*
  • Betula / immunology*
  • Dinoprostone / metabolism
  • Enzyme-Linked Immunosorbent Assay
  • Humans
  • Leukotriene B4 / metabolism
  • Ozone / analysis*
  • Pollen / immunology*
  • Skin Tests


  • Air Pollutants
  • Allergens
  • Leukotriene B4
  • Ozone
  • Dinoprostone

Grant support

The study was supported by a grant of the German Research Council (Deutsche Forschunsgemeinschaft, DFG, TR467/5-1 and ME 179/3-1) (CTH and AM), the HWP grant from of the Technische Universität München (SG), and CK Care, Christine Kühne Center for Allergy Research and Education. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.