Study On Immune Etiological Mechanism Of Unexplained Recurrent Spontaneous Abortions

Spontaneous abortion is one of the most common complications of pregnancy. Recurrent spontaneous abortion (RSA), defined as the occurrence of three or the more spontaneous abortion, occurs in about 0.8 to 1% of pregnant women. The search for the etiologies of RSA have led to current estimates of about 5% due to chromosomal anomalies, 17% due to endocrinologic abnormalities, 5% due to infectious etiologies, 5-10% due to anatomic problems, and about 3-5% attributable to humoral anti-phospholipid antibodies. All these well-established mechanisms put together account for only about 40-60% of the cases of RSA, with a substantial proportion of cases remaining "unexplained". It is generally accepted that a successful pregnancy depends on preventing potentially harmful maternal immune response of local uteroplacental immunosuppression, this has generated great interest in the investigation of possible immunologic etiologies of pregnancy failure. Cellular immune mechanism have been suggested to play possible etiologic roles. Recently studies lead to the conclusion that Th1-based reactivity is associated with pregnancy failure and that normal pregnancy is biased in favor of a Th2-dominant status.since it appears that successful murine pregnancy occurs in a Th2-dominant situation and that Th1-type immunity is associated with pregnancy failure.Costimulatory molecules and receptor play a important role in the activation of T-cells. Both CD80 and CD86 are commonly expressed on APC and function as costimulatory molecules in T-cell cytotoxicity. Now that CD80 and CD86 are expressed on APC while their receptor CD28 and CD152 are expressed on T cells, it is possible that CD80+ cells at the fetomaternal interface play as a triggering structure of T cell activation, especially Th1 subpopulation. The combine of CD86 and CD 28 molecules can increase expression level of IL-4, which induced the Th1 dominant response and inflammatory processes. Furthermore CD28 molecules inhibit the Th1 dominant response induced by CTLA4 and, increase the Th2 cytokines production.The main way of T-cell clonal clearance is apoptosis, while the Fas/FasL system leading to apoptosis. The interaction between Fas and FasL play a important role in clonal clearance, immune tolerance, immune excuse, and immune response. During pregnancy, placental trophoblasts express a large account of FasL to activate maternal leucocytes via Fas/FasL signal, and induce apoptosis of activated maternal leucocytes. The increment of apoptosis may be an important pathologic process in RSA. Meanwhile, the decreased expression of FasL on placental trophoblasts, which destroy the immunoligic tolerance between the mother and fetus, may be one of the important pathogenesis of RSA. Th1- and Th2-type cells have different sensitivity to apoptosis induced by Fas/FasL system, as the apoptosis of Th1 cells are quicker than Th2 cells.In this study, the relationships of RSA with Th1-and Th2-type cytokines, cositmulatory molecular B7:CD28/CTLA4 system, and Fas/FasL system were explored, in order to further explore the etiologic mechanism of RSA, and modify the imbalance of Th1- and Th2-type cytokines during RSA.First, by using collagenase and trypsinase digestion method human villus trophoblasts were isolated. Cells were observed by phase contrast microscopy to identify their morphologies. The characterizes of these cells were identified by detecting vimentin and cytokeratin expression with immuno-histochemistry staining. Compared maternal reactivity toward placental antigens in women with a history of successful pregnancy with that in women with a history of RSA. This was done by coculturing maternal peripheral blood mononuclear cells (PBMC) with autologous placental trophoblasts and also by stimulating maternal PBMC with nonspectic mitogen PHA. Pre-coated ELISA-kits were used for quantitative determination of INF-( and IL-10 in the supernatants of MLPR cultures and in serums to explore the relationship between RSA and Th1-and Th2-type cytokines. Using immuno-histochem...