D3.87 - Evaluation of CD63 as a Marker of Basophil Degranulation in the Assessment of IgE-mediated Allergic Immune Responses

The basophil activation test (BAT) is a comparatively new flow cytometry–based assay used to evaluate IgE-mediated allergic immune responses by detecting mediator release from basophils following allergen stimulation that may aid the correct diagnosis. The aim of this study was to evaluate the concordance between basophil degranulation, allergen-specific IgE (sIgE) and skin prick test (SPT) outcomes in patients with established pollen, house dust mite and honeybee venom allergy.

The study included 34 patients, exhibiting clinical symptoms and currently not on antihistamine therapy (26 male, 8 female, median age 39), with allergic sensitization to mixed grass pollen (n=13), house dust mite (n=15), and honeybee venom (n=6), and 11 sex- and age-matched controls without clinical history of allergic sensitization.  All participants were tested with BAT, using allergen extracts in line with their anamnestic sensitization, and the following cut-offs: > 15% for grass pollen and house dust mites, and >10% CD63+ basophils for honeybee venom. The percentage of degranulated basophils was compared to sIgE immunoblot results (kU/ml) and SPT outcome (flare/wheal diameter, mm) using Spearman’s correlation test. 

100% negative results were obtained for controls with all three tests. A significant positive correlation between BAT and sIgE was established in all patient subgroups as follows: Rho = 0.69, p = 0.01 for grass pollen, Rho = 0.63, p = 0.01 for house dust mite and Rho = 0.83, p = 0.05 for insect venom. In contrast, BAT correlated only with SPT wheal size in the house dust mite subgroup: Rho =0.56, p = 0.03.

In the same subgroup, two patients tested negative on BAT and sIgE, while positive for SPT (15/7, 14/5), alongside with 3 patients who tested negative on sIgE, but with positive BAT and SPT (15/7, 16/5, 18/5).

BAT shows a strong positive correlation with sIgE, and can improve diagnostic precision, when used in conjunction with established in vitro and in vivo methods.

Acknowledgements

This study was supported by the National Science Fund of Bulgaria [Grant No. KP-06-N73/6].