Allergen-induced basophil activation: CD63 cell expression detected by flow cytometry in patients allergic to Dermatophagoides pteronyssinus and Lolium perenne

Background In this study, we determined by flow cytometry the percentage of basophils activated after in vitro stimulation by allergens and expressing the CD63 marker. The diagnostic reliability of the technique was assessed as well as its correlation with other in vitro diagnostic parameters. Methods Fifty-three patients suffering from asthma and/or allergic rhinitis following sensitization to Dermatophagoides pteronyssinus and 51 patients sensitized to Lolium perenne were investigated. Twenty-four atopic patients not sensitive to these allergens and 38 healthy subjects were also selecte d as controls. The basophil activation test determines the percentage of ba sophils which express CD63 as an activation marker, by means of flow cytome try, after in vitro stimulation with allergen, using double labelling with monoclonal antibody anti-CD63-PE and anti-IgE-FITC. Results No differences in basal values (non-activated control) were found b etween sensitized patients, atopic controls and healthy controls. On the ot her hand, sensitized patients showed a significantly higher percentage of a ctivated basophils after stimulation by allergens in vitro than both contro l groups (P<0.001). We found a significant correlation between skin tests a nd basophil activation tests (r=0.72, P<0.001). We also found a positive an d significant correlation between basophil activation tests and histamine r elease tests (r=0.80, P<0.001), allergen-specific sulphidoleukotriene produ ction (r=0.7, P<0.001) and the occurrence of serum allergen-specific IgE (r =0.71, P<0.001). Conclusion The basophil activation test is a highly reliable technique in t he diagnosis of allergy to inhalant allergens. The sensitivity of the basop hil activation test was 93.3%, and its specificity 98.4%, when using a cut- off point of 15% activated basophils as positive result.