Högskolan i Skövde

Birch pollen is one of the major causes of seasonal allergies, affecting a large proportion of the European population. Current pollen forecasts are based on the number of grains in the atmosphere, although research suggests that the allergenicity per grain can vary significantly due to factors such as pollution and climate change that alter the grains. Flow cytometry (FCM) offers a promising approach to address these factors. This study aimed to investigate whether FCM can be used to assess the allergen load of birch pollen, whether clones of birch exhibit distinct levels of allergen content and, whether the level of reactive oxygen species, an indicator of cellular stress, correlates to allergen load. Sixteen samples of birch pollen were received from various organizations/institutions in Europe. To assess the allergen load, birch pollen samples were labeled with anti Bet v 1 antibodies and analyzed in FCM, while H2DCFDA was used to assess the ROS levels of the samples.

The results of the study did not provide definitive evidence that flow cytometry reliably assesses allergen load in birch pollen, however, the study demonstrated that antibody binding is detectable. No significant differences were found between birch clones, and this study did not yield evidence to support that the levels of ROS in birch pollen are correlated with the allergen load, only an indication of their relationship was observed. Further research with more replicates and improved protocols is needed to confirm these findings to possibly enhance pollen allergy forecasting and aid allergic individuals.

Popular scientific summary

Our body's defence system, the immune system, maintains our health by protecting us from harmful substances and invading pathogens. B cells are a specific cell type included in the immune system that secrete particular antibodies that attack a foreign invader. However, sometimes the immune system can react to harmless substances and produce a response that is commonly known as an allergy.

Trees often reproduce through wind pollination, in which pollen (male) from one tree is carried through the air to the flower (female) of another tree of the same species. Pollen allergies are seasonal allergies that by inhalation can trigger an immune reaction in the body, resulting in troublesome symptoms such as sneezing and itching of the eyes, throat, and nose. Antibodies recognize proteins in pollen, named allergens. A large part of the population suffers from pollen allergies, and although not life-threatening, symptoms are often severe and thus limit the quality of life for affected individuals. Birch pollen is among the most allergenic, and allergies to birch are increasing. Pollen monitoring and forecasting are essential for managing pollen allergies, assisting individuals with when to avoid the outdoors. The standard method for monitoring pollen involves collecting airborne pollen and manually counting the grains under a microscope. However, the quantity of pollen in the air does not necessarily reflect the potency to trigger allergic reactions, as allergen content can vary within the same species. Pollution and climate change can place stress on trees, ultimately altering the allergenic potential of their pollen. Measuring allergen content may thus offer a more accurate assessment than current forecasts.

This study will support ongoing research at the Pollen Laboratory, University of Gothenburg, which aims to identify areas in Gothenburg with higher allergen content in pollen. Ultimately, the goal is to track the movements of these grains for improved pollen forecasts. The aim of this study was to explore if flow cytometry can be used to assess; allergen levels in birch pollen, whether there is different allergen content in birch clones, and if the levels of reactive oxygen species (ROS), an indicator of stress, are connected to allergen load in pollen.

Flow cytometry is a technique that rapidly analyses particles in a suspension. When hit by a laser, the particles emit light which is translated into values. Antibodies, specific for birch pollen allergens, conjugated to a dye that fluoresces at a specific wavelength were used to detect the allergen attached to the pollen. From the analysis, a value of the medium fluorescence intensity was gathered and used to compare the allergen load. The results concluded that there was not enough evidence to definitively support that flow cytometry is a reliable method for assessing allergen loads in birch pollen. Although a statistical significant difference was observed between some samples and the results suggest variability in the allergen load of the samples, the limited amount of data prevents a definite conclusion to be drawn.

To assess the levels of ROS, pollen was stained with a compound that fluoresces when reacting with ROS. The analysis concluded that there was not enough evidence to support that the levels of ROS in birch pollen are correlated with the allergen load, only an indication that it does.