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Problem The initiation of labor is accompanied by alterations in the level of maternal immune tolerance toward fetal antigens. It is a complex molecular response leading to a brief activation of the maternal immune system with an accompanying capacity to restrict this same activation. The aim of our study was to evaluate the subpopulation of regulatory T cells (Tregs) and B7-H4 macrophages in the decidua basalis during cesarean sections performed on patients in various stages of labor. Method of study The decidual tissue samples evaluated in our study were obtained from 23 pregnant women who underwent cesarean sections at term. Moreover, the patients were divided into three subgroups according to the progression of labor at the time of the cesarean. The presence of Treg cells and B7-H4 positive macrophages were analysed by fluorescence-activated cell sorter. Results The percentages of FOXP3+ cells in the subpopulation of CD25+ CD4+ T lymphocytes found in the deciduas of patients decreased with the successive stages of labor, while the percentages of B7-H4 positive cells in the macrophage subpopulation remained almost constant. Conclusion These changes in the Treg cell subpopulation in the decidua would seem to be related to a brief activation of the maternal immune system as labor begins and lack of analogical changes in the subpopulation of decidual suppressive B7-H4+ macrophages that enable the restriction of this same activation as labor progresses.

Problem Alterations in RCAS1 (a receptor-binding cancer antigen expressed on SiSo cells) expression in the placenta and decidua may be related to the regulation of the process of maternal immune tolerance against fetal antigens. Moreover, it has been demonstrated that the occurrence of the spontaneous beginning of stillbirth is related to a decrease in the placental expression of RCAS1. There are no data currently available on the immune processes in decidua during stillbirth. The aim of this study was to evaluate the RCAS1 immunoreactivity level in decidua and to identify the cytotoxic immune cells present during labor, induced after intrauterine fetal death either with a combination of oxytocin (OT) and prostaglandins or with OT alone; a further objective was to assess the potential impact of these molecular alterations on the effectiveness of stillbirth induction. Methods The immunoreactivity of RCAS1, CD3, CD56, CD69, and CD25 was assessed by immunohistochemistry in 31 decidual samples derived from patients in whom the stillbirth occurred before the onset of labor. Results The RCAS1 immunoreactivity level was higher in a statistically significant manner in decidual tissue samples derived from patients in whom OT alone proved insufficient to induce labor after the diagnosis of intrauterine fetal death but required additionally the use of prostaglandins when compared with samples from women in whom stillbirth was induced successfully with OT alone. However, we did not observe any differences either in CD56 and CD3 positive cell presence or in CD25 and CD69 antigen immunoreactivity in the respective decidua of these two groups of patients. Conclusion The level of RCAS1 in decidua seems to influence the effectiveness of stillbirth induction.