Human Miscarriage Is Associated With Dysregulations in Peripheral Blood-Derived Myeloid Dendritic Cell Subsets.

Dendritic cells (DC) are critically involved in decisions related to the acceptance or rejection of the foreign fetal antigens by the maternal immune system. However, particularly for human peripheral blood DCs (PBDC), available literature is rather inconsistent and the factors regulating these cells are ill-defined. Here, we investigated the phenotype and functionality of different human PBDC subsets during normal and pathologic pregnancies and studied an involvement of human chorionic gonadotropin (hCG) in PBDC regulation. Peripheral blood samples were obtained from normal pregnant women in all three trimesters, from first trimester miscarriage patients and from healthy non-pregnant women. Samples were analyzed for plasma hCG levels, for regulatory T (Treg) cell numbers, for frequencies of total and mature plasmacytoid (PDC) and myeloid (MDC1 and MDC2) PBDC subsets and for their cytokine secretion. In vitro assays, culturing PDC, MDC1 or MDC2 in the presence of two trophoblast cell lines, placenta explant supernatants or two hCG preparations were performed. The Treg-inducing capability of hCG- or non-hCG-treated stimulated MDC1 was assessed. Total and mature MDC1 and MDC2 frequencies increased during the first and second trimester of normal pregnancy, respectively. Miscarriage was associated with a reduced MDC1 and an increased MDC2 activation profile. PDC were not altered neither during normal pregnancy progression nor during miscarriage. In vitro, the culture of isolated PBDC subsets in the presence of placenta-derived factors impaired the maturation of MDC1 and differentially affected PDC maturation. An inhibitory effect on MDC1 and PDC maturation was also proven for the urine-derived hCG preparation. Finally, we observed a Treg cell elevation during early normal pregnancy that was not present in miscarriages. Stimulated MDC1 induced Treg cells in vitro, however, hCG was not involved in this process. Our findings suggest that during normal pregnancy PBDC subsets are differentially regulated dependent on gestational age. Miscarriage seems to be associated with dysregulations in the myeloid PBDC subsets and with disturbances in Treg cell frequencies. Moreover, our results propose an interdependency between MDC1 and Treg cells during early pregnancy. hCG, although shown to impair MDC1 maturation, does not seem to be a key regulator of PBDC alterations during pregnancy.

JEG-3 Trophoblast Cells Producing Human Chorionic Gonadotropin Promote Conversion of Human CD4+FOXP3- T Cells into CD4+FOXP3+ Regulatory T Cells and Foster T Cell Suppressive Activity.

The pregnancy hormone human Chorionic Gonadotropin (hCG) reportedly modulates innate and adaptive immune responses and contributes thereby to fetal survival. More precisely, hCG has been shown to support human Treg cell homing into the fetal-maternal interface and enhance number and function of Treg cells in murine pregnancy. Here, we aimed to study whether hCG and hCG-producing human trophoblast cell lines induce Treg cells from CD4+FOXP3- T cells and promote T cell suppressive activity. CD4+FOXP3- T cells were isolated from peripheral blood of normal pregnant women and cultured in the presence of hCG-producing (JEG-3, HTR-8) and non-producing (SWAN-71) cell lines. To confirm the participation of hCG in Treg cell conversion, the experiments were performed in the presence of anti-hCG and additional experiments were run with recombinant or urine-purified hCG. After culture the number of CD4+FOXP3+ Treg cells as well as the suppressive capacity of total T cells was assessed. hCG-producing JEG-3 cells as well as recombinant and urine-purified hCG induced CD4+FOXP3+ Treg cells from CD4+FOXP3- T cells. Blockage of hCG impaired Treg cell induction. Moreover, hCG-producing JEG-3 cells increased suppressive activity of CD4+FOXP3- T cells through an antigen-independent pathway. Our results propose another mechanism through which hCG modulates the female immune system during pregnancy in favor of the fetus.

Low molecular weight heparin modulates maternal immune response in pregnant women and mice with thrombophilia.

PROBLEM: Thrombophilia is associated with pregnancy complications. Treatment with low molecular weight heparin (LMWH) improves pregnancy outcome, but the underlying mechanisms are not clear. METHODS OF STUDY: We analyzed Treg frequency in blood from thrombophilic pregnancies treated with LMWH (n = 32) or untreated (n = 33) and from healthy pregnancies (n = 39) at all trimesters. Additionally, we treated pregnant wild-type, heterozygous and homozygous factor-V-Leiden (FVL) mice with LMWH or PBS and determined Treg frequency, pro-/anti-inflammatory cytokine levels and Caspase-3-activity in placenta and decidua. RESULTS: Treg frequencies were increased in second and third trimester in LMWH-treated thrombophilic pregnancies compared to controls. Treg levels were comparable to those of normal pregnancies. Homozygous FVL mice had decreased decidual Tregs compared to wild-type mice. LMWH treatment normalized Tregs and was associated with increased decidual IL-10 mRNA. LMWH diminished Caspase-3-activity in mice of all genotypes. CONCLUSION: We demonstrated anti-apoptotic and anti-inflammatory effects of LMWH in pregnant FVL mice. LMWH increased Treg levels in mice and humans, which suggests benefits of LMWH treatment for thrombophilic women during pregnancy.