Influence of Environmental Pollution on Basophil Reactivity to Birch Pollen Allergens in Atopic and Non-Atopic Subjects.

BACKGROUND

Sensitization to birch pollen is a major contributor to allergic rhinitis in Europe, with sensitization rates in many countries from 10% to 20% of the general population. Growing evidence suggests that air pollution enhances the allergenicity of pollen; however, the clinical consequences of this co-exposure remain poorly understood. This study investigated whether air pollution intensifies birch pollen allergenicity and assessed its effects on symptom severity and basophil activation in allergic and non-allergic individuals.

METHODS

Fifty birch-allergic patients and twenty-five non-atopic controls were examined over two consecutive pollen seasons (2023-2024). Daily nasal, ocular, and asthma symptoms were recorded using a mobile application. Ambient air pollutants (PM2.5, PM10, and O3) and birch pollen concentrations were continuously monitored in Kraków. Basophil activation tests (BAT) were performed using commercial birch pollen extracts, Bet v1 allergen, and natural pollen collected from highly and less polluted areas. Basophil activation was quantified by CD63 expression using flow cytometry.

RESULTS

Asthmatic symptoms showed significant positive correlations with both birch pollen and PM concentrations (p < 0.05), especially in 2023. Pollen collected from polluted sites induced significantly stronger basophil activation compared with pollen from less polluted areas (p < 0.0001). The magnitude of basophil activation correlated with serum IgE levels to birch and Bet v 1, as well as with clinical symptom scores.

CONCLUSIONS

Air pollution enhances the allergenic potency of birch pollen, resulting in heightened basophil activation and more severe allergic symptoms. These findings highlight the importance of integrating air pollution monitoring alongside pollen surveillance when assessing allergic disease burden and evaluating the effectiveness of allergen immunotherapy.