Background: The effects of pollen immunotherapy on effector cells of allergic inflammation, such as mast cells and basophils, are poorly understood.
Objective: For this reason, we conducted an open study on basophil allergen threshold sensitivity during birch pollen immunotherapy.
Methods: Basophil sensitivity was measured by CD63 flow cytometry in 14 patients with moderate-severe intermittent birch pollen rhinitis using four log allergen concentrations. In nine patients, we analysed the basophil sensitivity before and during treatment with subcutaneous birch immunotherapy (perennial scheme with allergoid). We also included eight birch-allergic donor subjects for IgG inhibition experiments and eight control subjects.
Results: There was a decrease in basophil allergen threshold sensitivity after 2, 3, and 5 months of immunotherapy. This decrease was correlated with an improvement in patients' symptoms measured on a visual analogue scale. The serum obtained after immunotherapy induced a significant decrease in allergen threshold sensitivity in donor birch-allergic basophils. This inhibition was not observed after IgG depletion from the serum.
Conclusions: In this study, we showed that birch immunotherapy-induced IgG antibodies are associated with a reduction in basophil allergen threshold sensitivity. Further studies are needed to show whether the changes in basophil sensitivity are of clinical relevance in pollen immunotherapy.