RCAS1 Decidual Immunoreactivity during Stillbirth: Immune Cell Presence and Activity

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. 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. 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. The level of RCAS1 in decidua seems to influence the effectiveness of stillbirth induction.