Objective To determine the level of interleukin (IL)-10 in sera and culture supernatants of CD4+CD25+T cells from children with atopic dermatitis (AD),and to evaluate its relationship with clinical course and severity of AD.Methods Totally,46 children with AD and 31 healthy controls were included in the study.All the patients were divided into 3 groups,i.e.,mild (n =10),moderate (n =16) and severe (n =20) group,according to severity scoring of atopic dermatitis (SCORAD) score.Venous blood samples were obtained from the patients and healthy controls.CD4+CD25+ regulatory T cells were separated from the blood samples by magnetic cell sorting (MACS) system in two steps and cultured in vitro.Enzyme linked immunosorbent assay (ELISA) was conducted to quantify the level of IL-10 in sera and culture supernatants of CD4+CD25 + T cells from these subjects.Analysis of variance was carried out to compare the level of supematant and serum IL-10 between the patients and controls,and Pearson correlation analysis to assess the relationship between the level of IL-10 and SCORAD score.Results The patients with mild,moderate and severe AD showed a similar serum IL-10 level compared with the healthy controls ((43.10 ± 25.07) pg/ml,(68.40 ± 36.65) pg/ml and (55.55 ± 41.97) pg/ml vs.(58.27 ± 36.84) pg/ml,all P ＞ 0.05).The level of supernatant IL-10 secreted by CD4+CD25+ T cells from the controls was significantly higher than that from the patients with severe AD ((55.15 ± 11.15) pg/ml vs.(27.25 ± 7.01) pg/ml,P ＜ 0.05),but similar to that from the patients with mild and moderate AD ((52.96 ± 11.69) pg/ml and (49.86 ± 9.18) pg/ml,respectively,both P ＞ 0.05).The level of secreted IL-10 was negatively correlated with SCORAD score (r =－0.757,P ＜ 0.01),whereas the serum level of IL-10 showed no statistical correlation with SCORAD score.Conclusion CD4+CD25+ T cells and IL-10 may be implicated in the development of AD.