Chronic urticaria sera increase basophil CD203c expression.

Background: Approximately 40% of patients with chronic idiopathic urticaria have antibodies to the alpha subunit of the high-affinity IgE receptor. CD203c is a basophil activation marker known to be upregulated by cross-linking of the FcepsilonRIalpha receptor and may serve as a useful marker to identify these patients.

Objective: The primary objective was to assess the affect of sera from patients with chronic idiopathic urticaria on basophil CD203c expression. Secondary objectives were to correlate CD203c expression with basophil histamine release and size of the autologous serum skin test and to determine whether the mechanism is mediated by an IgG antibody.

Methods: Sera were obtained from patients with chronic idiopathic urticaria and positive autologous serum skin test or negative autologous serum skin test and normal controls. Sera were incubated with donor whole blood. Activated basophils from whole blood were identified by flow cytometry on the basis of the presence of CD203c on high-expressing IgE positive cells.

Results: Incubation of donor basophils with sera from patients with chronic idiopathic urticaria and positive autologous serum skin test demonstrated significant upregulation of CD203c. IgG depletion of representative sera from patients with chronic idiopathic urticaria resulted in significant decrease in CD203c expression on donor basophils. CD203c expression correlated with basophil histamine release and the size of the autologous serum skin test.

Conclusion: Sera from patients with chronic idiopathic urticaria and positive autologous serum skin test significantly upregulate basophil CD203c and correlate with basophil histamine release.

Clinical Implications: This article describes an activation marker on basophils whose expression is increased by sera from patients with chronic idiopathic urticaria.