Previous studies in our laboratory showed a dose-dependent and hormone-specific increase in CD154 expression in T cells from females with systemic lupus erythematosus (SLE). This present study investigates if the estrogen-dependent increase in CD154 expression is due to stabilization of the messenger RNA. T cells from female SLE patients and controls were cultured for 18 h in serum-free medium without and with estradiol 17-beta (10(-7) M). T cells were either unstimulated (resting) or were activated by further culture on anti-CD3 coated plates. Actinomycin D (25 microg/mL) was added to parallel cultures to inhibit new messenger RNA synthesis. CD154 messenger RNA stability was assessed by reverse-transcription polymerase chain amplification. Resting SLE (n = 10, P = 0.88) and normal (n = 7, P = 0.65) T cells showed no significant differences in message stability in response to estradiol. CD154 messenger RNA was also not significantly stabilized in activated SLE (n = 10, P = 0.15) or activated normal (n = 6, P = 0.077) T cells in response to estradiol. These findings indicate that the estrogen-dependent increase in CD154 in SLE T cells is not due to stability of the mRNA. These data are consistent with the postulate that estradiol stimulates CD154 transcription in SLE T cells.