• Ann De Swerdt, Caroline Van Den Keybus, Ahmad Kasran, Pascal Cadot, Karen Neyens, Lieve Coorevits, Anne-Marie Kochuyt, Hugo Degreef, and Jan L Ceuppens.
• Division of Clinical Immunology, University Hospital, Katholieke Universiteit Leuven, Belgium.
• J. Allergy Clin. Immunol. 2005 Sep 1; 116 (3): 662-7.

BackgroundApproximately 40% to 50% of patients with chronic idiopathic urticaria (CIU) have functional IgG autoantibodies against FcepsilonRIalpha or IgE, which induce histamine release from basophils and cutaneous mast cells. A positive autologous serum skin test response is believed to reflect the presence of these autoantibodies.ObjectiveWe sought to further define the functional properties of and develop a sensitive functional assay for detection of autoantibodies in patients with CIU.MethodsSera from patients with CIU (n=61) and sera from healthy control subjects (n=23) were incubated with donor basophils. Activation of basophils was determined on the basis of CD 63 surface expression, as analyzed on a FACScan flow cytometer.ResultsA positive basophil activation test result was found in 51% of patients with CIU, and basophil-activating properties were present in the IgG fractions of sera. When both the in vitro test and the autologous serum skin test were considered, basophil/mast cell-activating autoantibodies were present in 62% of the patients. Patients with a positive basophil activation test result had a significantly higher prevalence of other autoantibodies, had more severe urticaria, and were more likely to have angioedema.ConclusionThe results demonstrate the presence of basophil-activating autoantibodies in about 50% of patients with CIU. The data support the autoimmune cause of the disease and provide a simple test for detection of these autoantibodies.

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