Is Lolium pollen from an urban environment more allergenic than rural pollen?

BACKGROUND: Allergy to grass pollen is a highly prevalent allergic disease. Hay fever is more predominant in urban than in rural areas, despite the increasingly smaller areas of surrounding grassland. The effect of vehicle exhaust pollutants, mainly diesel particles, and other industrial sources of atmospheric pollution leading to plant damage has been implicated in this phenomenon.
OBJECTIVE: This study compared the in vivo and in vitro allergenicity of pooled samples of Lolium perenne grass pollen harvested from 10 different urban areas with that of samples of the same pollen from 10 neighboring rural areas.
METHODS: Lolium perenne pollen from different parts of a city and from a nearby rural area was harvested in 1999 and 2000 during the peak pollination period. Protein composition was compared by SDS-PAGE and in vivo and in vitro IgE-binding capacity was compared by skin-prick tests, RAST-inhibition and measurement of the major allergen, Lol p 5.
RESULTS: In the two years under study, urban samples contained approximately twice the protein content of the rural samples. Biological activity and Lol p 5 content was higher in urban pollen than in rural pollen and showed differences in the two years under study.
CONCLUSIONS: The protein content and allergenicity of Lolium perenne pollen was higher in urban areas than in rural areas. These differences might explain why allergy to grass pollen is more prevalent in urban areas. This finding should be taken into account in diagnosis, preventive measures and specific immunotherapy.