Abstract: Objective To investigate if the estrogen-dependent increase in CD154 expression in T cells of patients with systemic lupus erythematosus （SLE） is due to alterations in its mRNA stability. Methods T cells isolated from 10 female patients with SLE and 7 normal controls were cultured for 18 hours in serum-free medium with or without 10-7 mol/L of 17β-estradiol . Some of the T cells were then harvested and subjected to further culture in anti-CD3-coated plates for activation. Actinomycin D, 25 μg/mL, was added to the parallel cultures to inhibit further synthesis of mRNA. Unstimulated resting cells served as control. The expression of CD154 mRNA was assessed by reverse-transcription PCR. Results The average levels of CD154 mRNA relative to GAPDH mRNA were 75.5 and 73.6 in resting SLE T cells cultured with and without estradiol, respectively （P = 0.88）, 76.3 and 74.3 in resting normal T cells respectively （ P = 0.65）. No difference was observed in the stability of mRNA between SLE and normal control resting T cells in response to estradiol. After activation with anti-CD3 antibody, the average levels of CD154 mRNA relative to GAPDH mRNA were 86.8 and 54.5 in estradiol-stimulated and unstimulated SLE T cells respectively （P = 0.15）, 87.7 and 68.1 in normal T cells respectively （P = 0.077）. There was no statistical difference in the stability of mRNA between SLE and normal activated T cells stimulated by estradiol. Conclusion These findings suggest that the estrogen-dependent increase in CD154 of SLE T cells is not due to the alteration in stability of mRNA.

Key words: CD154, SLE, estrogen, T cell, mRNA stability