Objective To investigate DNA methylation markers in the whole blood of patients with systemic lupus erythematosus(SLE),in hope to facilitate the evaluation of SLE severity.Methods Whole blood samples were obtained from 58 patients with SLE(including 14 cases of severe SLE,25 moderate SLE,19 inactive SLE)and 50 healthy controls.Bisulphite sequencing was performed to determine the methylation status of interleukin-2 common receptor gamma chain(IL-2RG)promoter region,and real-time reverse transcriptionPCR to quantify the expression level of IL-2RG mRNA,in these subjects.Results The methylation level of IL2RG promoter region was 0.217 ± 0.140,0.325 ± 0.230,0.342 ± 0.085 and 0.175 ± 0.036 in the patients withsevere,moderate and inactive SLE and healthy controls,respectively.A significant increase was observed in the methylation level of IL-2RG promoter region in the patients with inactive SLE compared with the patients with severe SLE and healthy controls(both P ＜ 0.01),and in the patients with SLE compared with the healthy controls(0.263 ± 0.047 vs.0.175 ± 0.036,P ＜ 0.05).The expression level of IL-2RG mRNA was significantly lower in the patients with SLE than in the healthy controls(2.550 ± 0.823 vs.4.293 ± 1.283,P ＜ 0.05).A negative correlation was observed between the expression level of IL-2RG mRNA and methylation level of IL2RG promoter region in 20 patients with SLE(r =-0.44,P ＜ 0.05).Conclusion The methylation status of IL2RG promoter region is statistically higher in patients with SLE than in healthy controls,and significantly different between patients with active SLE and those with stable SLE.