The study of characteristic and function of mononuclear cell infiltrating the decidua in early human pregnancy

Abstract

The immunological mechanisms which prevent maternal rejection of the fetus have not yet been fully elucidated. Thus, it is very important to clarify the immunological environment of the decidual tissue existing at the interface between the fetus and the mother. In this study, the characteristics of mononuclear cells (MNC) infiltrating the decidual tissue (D-MNC) were investigated by using monoclonal antibodies specific for various surface antigens of MNC. In addition, the functions of D-MNC were also studied.
In comparison to peripheral blood MNC (P-MNC), in D-MNC, CD8⁺ cells were more numerous and CD4⁺/CD8⁺ ratio was decreased. Furthermore, two-color staining showed that 81% of CD8⁺ cells were CD11b^- cells. CD14⁺ cells were also increased. Immunohistological studies showed that CD3⁺ cells were present around the epithelial glands at the decidua spongiata, but not in the decidua compact. CD8⁺ cells were observed in greater number than CD4⁺ cells, and these CD8⁺ cells were CD11b^- cells. However, IL-2 receptor positive cells were not seen.
The functions of D-MNC were compared with that of P-MNC. Functions evaluated in this studies were PHA response, IL-2 response, suppressive activity and natural killer activity. The PHA reactivity of D-MNC was lower that of P-MNC, although the IL-2 response and suppressor activity of D-MNC was higher. Therefore, the activity of T-cells in the decidua was high, but suppressor cells and suppressor factors derived from decidual cells suppressed the function of D-MNC. The NK activity of D-MNC was lower than that of P-MNC.
In conclusion, although cytotoxic T-cells were more numerous in the decidua compacta than in peripheral blood, the action of suppressor cells and suppressor factors was consideredto prevent these cells from rejecting the fetus.