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The present study evaluated the secretions of interleukin (IL)-1beta and tumor necrosis factor (TNF) alpha by fetal membranes stimulated with group B streptococci (GBS) and lipopolysaccharide (LPS). The aim was to evaluate the initial response of full-thickness membranes to the microbial insult using an in vitro experimental model that allowed testing of the individual contributions of amnion and choriodecidua to stimulation. Full-thickness membranes were obtained after delivery by elective cesarean section from women at 37-40 wk of gestation without evidence of active labor. The membranes were mounted in Transwell devices, physically separating the upper and lower chambers. The LPS (500 ng/ml) or GBS (1 x 10(6) colony-forming units/ml) was added to either the amniotic or choriodecidual surface, and accumulation of IL-1beta and TNFalpha were measured in both compartments using a specific ELISA. Fetal membranes followed different patterns of secretion of proinflammatory cytokines that depended on the side to which the stimulus was added or the nature of the stimulus itself. The TNFalpha was secreted by amnion and choriodecidua in the presence of LPS or GBS, and stimulation with GBS induced a greater synthesis of IL-1beta than did stimulation with LPS. Choriodecidual tissue was more responsive than amniotic tissue, and this response tended to be higher even when the stimulation was only on the amniotic side. However, the amnion plays an active role in recognizing LPS or GBS, contributing a significant amount of TNFalpha. Thus, cooperative and bidirectional communications occur between amnion and choriodecidua in response to bacterial products, which include intermembranous cytokine traffic and signaling between tissues.

A system for transplanting invasive equine trophoblast (i.e., chorionic girdle) to ectopic sites has been developed as a means to study the differentiation of this tissue and to assess maternal immune responses to the conceptus tissue in a site outside the uterus. Chorionic girdle was isolated from Day 33 to 34 conceptuses and surgically placed into the vulvar mucosa or subdermal skin of recipient mares. Biopsy specimens of the graft sites for immunohistochemical staining were taken at weekly or biweekly intervals after grafting. Serum samples were collected from each recipient and tested for antibody to donor major histocompatibility complex (MHC) class I antigens using the lymphocyte microcytotoxicity assay. Transplanted trophoblast cells expressed differentiation markers associated with invading chorionic girdle and endometrial cup cells. The transplanted trophoblast cells were also labeled by an antibody to eCG. Strong cellular and humoral immune responses to the transplanted tissue were mounted by the recipients, similar to those occurring during normal equine pregnancy. Despite these responses, the invasive trophoblast transplants survived for at least 28 days after grafting and downregulated MHC class I antigens, as do the mature endometrial cup cells in equine pregnancy. These findings suggest that invasive equine trophoblast has the capacity to differentiate fully in equine nonuterine tissues, and that it can evade maternal immune responses independent of the physiological state of pregnancy and in sites other than the uterus.

In this study, the pattern of expression of class I major histocompatibility (MHC) antigens and mRNA on periimplantation blastocysts and term placental tissue was determined for the pig. Class I MHC antigens could not be detected immunohistochemically either on extra-embryonic membranes or on the embryonic portion of Day 14, 16, 22, and 25 blastocysts. Nor could class I MHC antigens be detected on the outer trophoblast epithelium and inner endodermal surface of the chorioallantoic membrane or on the outer and inner surfaces of the amnion at term. However, MHC class I antigens were detected on the vascular mesoderm found in both the chorion and amnion at term, and in Day 25 extra-embryonic membranes. Uterine endometrial cells and tissues and maternal peripheral blood leukocytes stained strongly for class I MHC antigens. There was a large difference in the intensity of class I MHC mRNA signal, detected by Northern blot analysis, in embryo/fetus-derived tissues compared to that in maternal tissues. The embryos appeared to express even less class I MHC mRNA than did the extra-embryonic membranes. In addition, in situ hybridization of Day 16 blastocysts indicated class I MHC mRNA to be ubiquitously expressed at low levels in embryos and extra-embryonic tissues compared to uterine endometrial tissue controls. Taken together, these results indicate that class I MHC antigens are either not expressed on the surface of the extra-embryonic/fetal membranes during gestation in the pig or are expressed at very low levels, and that specific mRNA is expressed at correspondingly low levels.

Interleukin (IL)-8 is a chemotactic cytokine that has been implicated in the etiology of infection-induced and normal human labor. In particular, IL-8 has been implicated in the processes of cervical ripening and rupture of fetal membranes because of its role in neutrophil activation and release of cellular matrix remodeling enzymes. In this study, we tested the hypotheses that IL-8 is released locally in the intrauterine environment from human amnion, choriodecidua, and placenta, and that IL-8 release from these tissues is increased by bacterial endotoxin, lipopolysaccharides (LPS), and inflammatory cytokines. IL-8 was released from human amnion, choriodecidual, and placental explants, with choriodecidua demonstrating the most abundant release. IL-8 release was significantly (multiple analysis of variance, p < 0.05) increased by LPS in a time- and dose-dependent manner from both choriodecidual and placental explants, but not from amnion explants. In addition, IL-1alpha (0.28 nM) and tumor necrosis factor alpha (TNFalpha, 10 nM) significantly (Student's t-test, p < 0.05) increased IL-8 release from placental explants 2- to 3-fold. These studies establish that the amnion, choriodecidua, and placenta are a source of IL-8 and demonstrate tissue-specific and differential regulation of IL-8 release by LPS, IL-1alpha, and TNF-alpha. These data support a role for IL-8 in a cascade of inflammatory events initiated by an intrauterine infection and resulting in activation of the labor process.