Abstract: Wang Yating, Shi Chunrui, Wu Yi, Shi Bei, Xiong Xiao, Zhou Lanxia Department of Dermatology and Venereology, The First Hospital of Lanzhou University, The First Clinical Medical College of Lanzhou University, Lanzhou 730000, China Corresponding author: Shi Chunrui, Email: stone7207@126.com 【Abstract】 Objective To explore the role of peripheral blood CD4+CD25+CD127low Treg cells, interleukin-17A （IL-17A） and IL-27 in the pathogenesis of chronic spontaneous urticaria （CSU）. Methods Peripheral blood samples were obtained from 37 patients with CSU （CSU group）and 40 healthy controls （control group）. Flow cytometry was performed to determine the percentage of CD4+CD25+CD127low Treg cells in the peripheral blood, and enzyme-linked immunosorbent assay （ELISA） to detect the serum levels of IL-17A and IL-27. Results The percentage of CD4+CD25+CD127low Treg cells in the peripheral blood （5.99% ± 2.72% vs. 9.07% ± 3.44 %, t = 4.325, P < 0.01） and the serum level of IL-27 （20.54 ± 7.65 ng/L vs. 26.63 ± 9.72 ng/L, t = 3.039, P = 0.003） were both significantly lower in the CSU group than in the control group. However, there was no significant difference in the serum level of IL-17A between the 2 groups （P = 0.529）. Among the patients with CSU, the level of IL-17A was negatively correlated with the percentage of CD4+CD25+CD127low Treg cells （r = -0.359, P = 0.029）, while the urticaria activity score （UAS） was uncorrelated with the levels of IL-17A and IL-27 as well as the percentage of CD4+CD25+CD127low Treg cells （r = -0.076, -0.083, -0.053 respectively, all P > 0.05）. Conclusion There may be Th17/Treg imbalance in the peripheral blood of patients with CSU, and IL-27 may be involved in the occurrence of CSU.