Relationship between changes in the 7-day urticaria activity score after treatment with omalizumab and the responsiveness of basophils to FcωRI stimulation in patients with chronic spontaneous urticaria

Abstract

Background About one-half of all patients with chronic spontaneous urticaria have low or less reactivity of the basophils to FcωRI stimulation. However, the differences in the clinical characteristics between patients who show normal and attenuated basophil reactivities to FcωRI stimulation are still unclear. Furthermore, it also remains unknown as to what factors induce the poor reactivity of basophils to FcωRI stimulation. Objective The aim of the study is to investigate the differences in the clinical characteristics between patients who show normal and attenuated basophil reactivities to FcωRI stimulation. Methods We compared the clinical characteristics, including the autologous serum skin test-positive rates, serum concentrations of anti-IgE and anti-FcωRIα autoantibodies, and the FcωRI-crosslinking ability of these autoantibodies between patients with a negative basophil activation test (BAT) (≤10% CD203chigh basophils, n = 9) and positive BAT (>10% CD203chigh basophils, n = 13). We also monitored the changes in the 7-day urticaria activity scores after treatment with omalizumab, as compared to the score at the baseline, between the BAT-positive and BAT-negative patients. Results The BAT-negative patients showed a significantly higher urticaria control test score than the BAT-positive patients (p = 0.01). There were no significant differences in the autologous serum skin test-positive rates, concentrations of anti-IgE and anti-FcωRIα autoantibodies, and the FcωRI-crosslinking ability of these autoantibodies between the 2 groups. After treatment with omalizumab for 35 days, the score decreased to under 15 (corresponding to controlled or mild chronic spontaneous urticaria) in all of the BAT-negative patients, whereas in 6 out of the 13 BAT-positive patients, the scores remained over 16 (corresponding to moderate or severe chronic spontaneous urticaria). Conclusions The weak reactivity of basophils to FcωRI stimulation may not be due to the desensitization of basophils by anti-IgE or anti-FcωRIα autoantibodies. The time to response to omalizumab might differ between BAT-negative and BAT-positive patients with chronic spontaneous urticaria.