Detection of serum IgG autoantibodies to FcεRIα by ELISA in patients with chronic spontaneous urticaria

Abstract

Background: Mast cells are a key effector cell in the pathogenesis of chronic spontaneous urticaria (CSU) and activated by circulating FcεRI-specific IgG as well as IgE. This study evaluated the prevalence of circulating autoantibodies to FcεRIα in the sera of CSU patients.

Methods: Eighty-eight patients with CSU and 76 healthy controls (HCs) were enrolled. To detect circulating autoantibodies (IgG/IgA/IgM) to FcεRIα, ELISA was done using YH35324 (as a solid phase antigen), and its binding specificity was confirmed by the ELISA inhibition test. The antibody levels were presented by the ratio of YH35324-preincubated to mock-preincubated absorbance values. Clinical and autoimmune parameters, including atopy, urticaria activity score (UAS), serum total/free IgE levels, serum antinuclear antibody (ANA) and autologous serum skin test (ASST) results, were assessed. The autoimmune group was defined if CSU patients had positive results to ASST and/or ANA.

Results: The ratio of serum IgG to FcεRIα was significantly lower in CSU patients than in HCs (P<0.05), while no differences were noted in serum levels of IgG to recombinant FcεRIα or IgA/IgM autoantibodies. The autoimmune CSU group had significantly lower ratios of IgG/IgA (not IgM) autoantibodies to FcεRIα than the nonautoimmune CSU group (P<0.05 for each). No significant associations were found between sex, age, atopy, urticaria duration, UAS, or serum total/free IgE levels according to the presence of IgG/IgA/IgM antibodies.

Conclusions: This study confirmed the presence of IgG to FcεRIα in the sera of CSU patients, especially those with the autoimmune phenotype.

Fig 1. Comparison of serum IgG, IgA, and IgM autoantibodies to FcεRIα between patients with chronic spontaneous urticaria (CSU) and healthy controls (HCs).

The results were presented by the IgG ratio of YH35324-pretreated to mock-treated values (A), the IgG ratio of rhFc-pretreated to mock-treated value (B), the IgA ratio of YH35324-pretreated to mock-treated value (C) and the IgM ratio of YH35324-pretreated to mock-treated value (D). Horizontal lines and dotted lines show median values and cutoff values of each autoantibody to FcεRIα respectively. P values were evaluated by Mann-Whitney test. rhFc, recombinant human Fc; NS, no statistical significance.

Fig 2. Comparisons of serum IgG/IgA/IgM levels to FcεRIα between the autoimmune and nonautoimmune groups.

The results were presented by the IgG ratio of YH35324-pretreated to mock-treated value (A), the IgA ratio of YH35324-pretreated to mock-treated value (B) and the IgM ratio of YH35324-pretreated to mock-treated value (C). The autoimmune group was defined if CSU patients have a positive result to ASST or ANA test. Horizontal lines and dotted lines show median values and cutoff values of each autoantibody FcεRIα respectively. P value was evaluated by Mann-Whitney test. ASST, autologous serum skin test; ANA, antinuclear antibody; NS, no statistical significance.