Abstract: DING Yan*, XIAO Rong, ZHANG Yan, MENG Bing-xin, SU Jian-ying, HAN Ke. *Department of Dermatology and Venereology, Hainan Provincial People's Hospital, Haikou 570102, China 【Abstract】 Objective To detect the expressions of CD70 mRNA and protein and to determine the methylation status of CD70 gene promoter in T cells from patients with systemic lupus erythematosus（SLE）．Methods Peripheral blood CD4+ and CD8+ T cells were isolated from 15 patients with active SLE, 15 patients with inactive SLE and 15 healthy control subjects． Real-time quantitative reverse transcription-PCR was carried out to quantify the mRNA expression of CD70, flow cytometry to determine the frequency of CD4+CD70+ and CD8+CD70+ T cells, and bisulfite sequencing to evaluate the methylation status of CD70 gene promoter in CD4+ and CD8+ T cells． Differences in these parameters among these groups were analyzed by one-factor analysis of variance and SNK-q test. Results Compared with the healthy controls, the patients with active SLE and inactive SLE showed a significant increase in CD70 mRNA expression in CD4+ T cells （0.82 ± 0.12 and 0.73 ± 0.11 vs. 0.45 ± 0.09, F = 53.017, P < 0.01） and in the frequency of CD70+CD4+ T cells （80.30% ± 11.04% and 66.80% ± 3.98% vs. 12.48% ± 3.45%, F = 311.517, P < 0.01）. Also, the expression of CD70 mRNA in CD4+ T cells and the frequency of CD70+CD4+ T cells were significantly higher in patients with active SLE than in patients with inactive SLE （both P < 0.05）. There was a positive correlation between the frequency of peripheral CD70+CD4+ T cells and disease activity in SLE in these patients（r = 0.792, P < 0.01）. The average methylation index of the region between －600 bp and －300 bp of CD70 gene promoter in CD4+ T cells was 0.32 ± 0.05 and 0.36 ± 0.05 respectively in the patients with active and inactive SLE, significantly lower than that in the healthy controls （0.62 ± 0.05, F = 152.64, P < 0.01）, and the patients with active SLE showed a significantly lower methylation index than those with inactive SLE （P < 0.05）. Conclusions The CD70 gene promoter in CD4+ T cells is significantly hypomethylated in patients with SLE, which may directly lead to the overexpression of CD70. 【Key words】 Lupus erythematosus, systemic; T-lymphocytes; Antigens, CD70; DNA methylation

Key words: T-lymphocytes, Antigens，CD70, DNA methylation