Biochemical characterisation and protein profile of icelandic birch pollen, as the potential sources of allergens

Birch pollen is a major trigger of allergic rhinitis and asthma in Northern and Central Europe. Environmental factors, including air pollution and natural particulate matter, may modify pollen biochemical composition and allergen expression, thereby influencing allergic disease burden. Iceland provides a unique low-anthropogenic, high-natural-dust environment for investigating these relationships. The aim of the study was to evaluate species- and environment-related differences in birch pollen composition and to assess their potential implications for allergic sensitization and respiratory health. Pollen samples of Betula pubescens and Betula nana were collected at multiple sites in Northern Iceland and compared with Betula pendula reference samples from Southern Poland. Pollen viability, biochemical composition (FT-Raman spectroscopy), total protein content, Bet v 1 concentration (ELISA), and protein profiles (SDS-PAGE) were analysed. Betula nana pollen exhibited reduced protein complexity, lower total protein and Bet v 1 concentrations, and lower lipid-to-sporopollenin ratios compared with B. pubescens and B. pendula . Substantial site-dependent variability was observed among Icelandic populations. A putative hybrid showed reduced pollen viability and intermediate biochemical characteristics. The 25 kDa protein band represented a major differentiating feature, whereas major proteins of molecular weight 16–18 kDa, widely recognized as the most potent allergens, were weakly expressed in most samples. Marked species- and environment-dependent differences in birch pollen composition were identified in Iceland. The reduced quantity of protein subunits of potential immunoreactive properties, observed in B. nana suggests a potentially lower sensitization capacity. These findings may contribute to improved risk assessment and management of pollen-related allergic diseases in Nordic populations.