Comparative studies of functional and binding assays for IgG anti-FcεRIα (α-subunit) in chronic urticaria

Background: Recent data suggest that a subpopulation of patients with chronic urticaria have an autoimmune disorder that is caused by the presence of antibodies to the IgE receptor. The actual incidence of these antibodies is uncertain. Objective: We sought to assess the incidence of autoimmunity to the IgE receptor in patients with chronic urticaria and to compare functional and binding assays, Methods: We isolated skin mast cells and studied a large number of patient sera (68) for their ability to activate these cells and isolated basophils. We then compared the results with those obtained by immunoblotting using cloned alpha-subunit of the IgE receptor. Results: Sera from patients with chronic urticaria released significant histamine (>15% of basal) on incubation with basophils (48%) and mast cells (46%). By immunoblotting we obtained positive results in 64% of subjects tested and also identified a small subpopulation that is active on cells but does not bind Fc(epsilon)RI(alpha). Conclusion: Our data suggest that approximately 45% to 50% of patients with chronic urticaria have a cutaneous autoimmune disorder. Immunoblotting may provide a rapid screening method for anti-Fc(epsilon)RI(alpha) detection in such patients.