Exposure to cadmium-contaminated soils increases allergenicity of Poa annua L. pollen

Pollution is considered as one main cause for the increase of allergic diseases. Air pollutants may cause and worsen airway diseases and are probably able to make pollen allergens more aggressive. Previous studies looked at traffic-related air pollution, but no data about the effects of polluted soils on pollen allergens are available. We aimed to assess the effects of plant exposure to cadmium-contaminated soil on allergenicity of the annual blue grass, Poa annua L, pollen.

Poa plants were grown in soil contaminated or not contaminated (control) with cadmium. At flowering, mature pollen was analyzed by microscopy, to calculate the percentage of pollen grains releasing cytoplasmic granules, and by proteomic techniques to analyze allergen proteins. Allergens were identified by sera from grass pollen-allergic patients and by mass spectrometry.

Pollen from Cd-exposed plants released a higher amount of allergenic proteins than control plants. Moreover, Cd-exposed pollen released allergens-containing cytoplasmic grains much more promptly than control pollen. Group 1 and 5 allergens, the major grass pollen allergens, were detected both in control and Cd-exposed extracts. These were the only allergens reacting with patient's sera in control pollen, whereas additional proteins strengthening the signal in the gel region reacting with patient's sera were present in Cd-exposed pollen. These included a pectinesterase, a lipase, a nuclease, and a secretory peroxydase. Moreover, a PR3 class I chitinase-like protein was also immunodetected in exposed plants.

Pollen content of plants grown in Cd-contaminated soils is more easily released in the environment and also shows an increased propensity to bind specific IgE.