Oxygen radical production by blood eosinophils is reduced during birch pollen season in allergic patients

SummaryBackground The eosinophil granulocyte takes part in allergic inflammatory diseases, like asthma and rhinitis. The aim of this study was to investigate the oxidative metabolism of the blood eosinophils and neutrophils from birch pollen allergic patients, during and after exposure to their allergen.Methods Thirteen birch pollen allergic patients, with seasonal symptoms of rhinitis, with or without asthma, were followed. The cells were purified using a percoll gradient and the MACS system. The eosinophil purity in all samples was >95%. The oxidative metabolism of both the PMN and the eosinophils was measured by means of a chemiluminescenee (CL) assay, with luminol or lucigenin as the amplifier, and using PMA (16nM) as the activator.Results In relative terms, the lucigenin CL by the eosinophils was 5‐10‐foId higher than that of the PMN, P= 0.002. The eosinophils of the birch pollen allergic patients produced less oxygen radicals during the season, compared to the reference group, measured both with luminol CL and lucigenin CL, P=0.01 and P= 0.02 respectively. Out of season, there was no difference. There was also no difference, during either period, between patients and references in PMN CL. Separating the eosinophils into hypodense and normodense fractions, showed a decreased oxidative metabolism by the hydrodense eosinophils.Conclusion We conclude that the eosinophils of birch pollen allergic patients have reduced production of oxygen radicals when the patients are exposed to their allergen, which could depend on higher amounts of hypodense eosinophils in the blood during season.