Objective: To clarify whether the down-regulation of CD25 on decidual T cells occurred at the activated T cells and was governed through reduced CD25 messenger RNA (mRNA) production. Design: Retrospective analysis and prospective study. Setting: University hospital and medical college. Patient(s): A total of 12 women receiving hysterectomies and 20 pregnant women having elective abortions were included. Intervention(s): The amount of CD25 mRNA in isolated T cells from peripheral blood, endometrium, and decidua was analyzed with real-time polymerase chain reaction and was compared after coculture with autologous cytotrophoblast cells. Main Outcome Measure(s): Expression levels of CD25 and CD25 mRNA before and after coculture. Result(s): The percentage of activated T cells expressing CD25 is lower in decidua than in peripheral blood but the opposite in regulatory T cells. Nevertheless, the amount of CD25 mRNA in decidual T cells did not decrease, instead of approaching that in corresponding fully activated T cells. In the coculture model, we found that the cytotrophoblast cells could induce the decreased expression of CD25 on T lymphocytes. However, there was no change in the amount of CD25 mRNA in T cells after coculture. Conclusion(s): This study demonstrates the effectiveness of the coculture model to study fetomaternal interactions and provides evidence that fetal cells may contribute to the control of maternal local immunity and that the decreased expression of CD25 on decidual T lymphocytes is not through the reduced CD25 mRNA level.
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