C5a-induced in vitro basophil activation in patients with chronic urticaria: a pilot study

BACKGROUND: Complement component 5a (C5a) might be involved in the formation of wheals in patients with chronic urticaria (CU). We sought to compare the in vitro responsiveness of basophils to C5a in patients with CU and in a control group. METHODS: Basophil surface expression of activation marker CD63 induced by C5a, anti-FceRI mAb or anti-IgE pAb was measured using flow cytometry in 17 patients with CU and in 10 healthy controls. RESULTS: Patients with CU showed significantly greater basophil CD63 surface expression induced by C5a (median [interquartile range]; 16.4% [13–25.1]; P = 0.011) than the group of healthy controls (10.7% [7.2–16.8]). In contrast, basophil CD63 response to anti-IgE and anti-FceRI was lower in the CU group (12.3% [6–36.3]; 25.9% [12.5–60.5]) than in the control group (51.7% [6.7–84.3]; 62.1% [9.7–89.2]), although not statistically significant. CONCLUSION: Results of this pilot study suggest that patients with CU might have an enhanced basophil response to stimulation with C5a, indicating that further studies in CU basophil responsiveness are needed.