Abstract: ZHANG Ming-hai, ZHAO Jian-bin *. *Department of Dermatology, First People's Hospital of Xuzhou, Xuzhou 221002, Jiangsu, China Corresponding author: ZHAO Jian-bin, Email:zhaojianb@sina.com 【Abstract】 Objective To investigate the possible role of interleukin （IL）-10 secreted by peripheral CD+CD25+ regulatory T （Treg） cells in the formation of seroresistance state in patients with syphilis. Methods Venous blood samples were obtained from 28 serofast patients with syphilis and 28 healthy controls. Flow cytometry （FCM） was performed to determine the proportion of CD4+CD25+IL-10+ T cells in peripheral CD4+ cells, and to quantify the protein expression of IL-10 in CD4+CD25+ Treg cells. Magnetic activation cell sorting （MACS） system was used to separate CD4+CD25+ Treg cells in high purity followed by the detection of IL-10 mRNA expression with real time PCR. Results A significant increase was observed in the proportion of CD4+CD25+IL-10+ T cells in peripheral CD4+ cells, as well as protein and mRNA expression levels of IL-10 in the serofast patients with syphilis compared with the healthy controls （all P < 0.01）. However, no statistical correlation was observed between rapid plasma reagent （RPR） titer and any of the above three parameters in these patients （all P > 0.05）. Conclusion The high level of IL-10 secreted by CD4+CD25+ Treg cells may contribute to the formation of seroresistance state in patients with syphilis.

Key words: IL-10