Abstract: Objective To detect the expression of CD70 in peripheral T lymphocytes of patients with systemic lupus erythematosus （SLE） and the effect of azacitidine, an inhibitor of DNA methylation, on it. Methods Blood samples were obtained from 10 patients with active SLE （SLEDAI score ≥5）, 10 patients with nonactive SLE （SLEDAI score < 5） and 10 normal human controls. Peripheral T lymphocytes were isolated and cultured for 72 hours. A part of the T lymphocytes from normal controls, which were cultured in the presence of azacitidine at 1 mol/L, served as the methylation-inhibited group. Semiquantitative reverse transcription PCR and flow cytometry were applied to detect the mRNA expression of CD70 and frequency of CD70+CD4+ cells in the cultured lymphocytes, respectively. Results The frequency of CD70+CD4+ lymphocytes was 14.55% ± 5.49% in normal control group, 85.25% ± 14.08% in active SLE group, 77.65% ± 18.77% in nonactive SLE group, and 81.54% ± 8.71% in methylation-inhibited group. Compared with the normal control group, a significant increase was observed in both the frequency of CD70+CD4+ lymphocytes （all P < 0.01） and the expression of CD70 expression （all P < 0.05） in other three groups. There was a positive correlation between the frequency of peripheral CD70+CD4+ lymphocytes and disease activity of SLE in patients （r = 0.72, P < 0.05）. Conclusions The elevated expression of CD70 appears to play a significant role in the immunologic disarrangement in SLE, and may act as a indicator of disease activity of this disease.

Key words: systemic lupus erythematosus, T-lymphocytes