Interleukin-17-producing decidual CD4+ T cells are not deleterious for human pregnancy when they also produce interleukin-4.

BACKGROUND: Trophoblast expressing paternal HLA-C antigens resemble a semiallograft, and could be rejected by maternal CD4+ T lymphocytes. We examined the possible role in human pregnancy of Th17 cells, known to be involved in allograft rejection and reported for this reason to be responsible for miscarriages. We also studied Th17/Th1 and Th17/Th2 cells never investigated before. We defined for the first time the role of different Th17 subpopulations at the embryo implantation site and the role of HLA-G5, produced by the trophoblast/embryo, on Th17 cell differentiation. METHODS: Cytokine production by CD4+ purified T cell and T clones from decidua of normal pregnancy, unexplained recurrent abortion, and ectopic pregnancy at both embryo implantation site and distant from that site were analyzed for protein and mRNA production. Antigen-specific T cell lines were derived in the presence and in the absence of HLA-G5. RESULTS: We found an associated spontaneous production of IL-17A, IL-17F and IL-4 along with expression of CD161, CCR8 and CCR4 (Th2- and Th17-type markers) in fresh decidua CD4+ T cells during successful pregnancy. There was a prevalence of Th17/Th2 cells (producing IL-17A, IL-17F, IL-22 and IL-4) in the decidua of successful pregnancy, but the exclusive presence of Th17 (producing IL-17A, IL-17F, IL-22) and Th17/Th1 (producing IL-17A, IL-17F, IL-22 and IFN-γ) cells was found in the decidua of unexplained recurrent abortion. More importantly, we observed that Th17/Th2 cells were exclusively present at the embryo implantation site during tubal ectopic pregnancy, and that IL-4, GATA-3, IL-17A, ROR-C mRNA levels increased in tubal biopsies taken from embryo implantation sites, whereas Th17, Th17/Th1 and Th1 cells are exclusively present apart from implantation sites. Moreover, soluble HLA-G5 mediates the development of Th17/Th2 cells by increasing IL-4, IL-17A and IL-17F protein and mRNA production of CD4+ T helper cells. CONCLUSION: No pathogenic role of decidual Th17 cells during pregnancy was observed. Indeed, a beneficial role for these cells was observed when they also produced IL-4. HLA-G5 could be the key feature of the uterine microenvironment responsible for the development of Th17/Th2 cells, which seem to be crucial for successful embryo implantation.

Nitric oxide and oxidative stress in placental explant cultures.

Placental explant culture, and cellular cytolysis and cellular differentiation have been previously studied. However, oxidative stress and nitric oxide profiles have not been evaluated in these systems. The aim of this study was to determine the release of lipid peroxidation and nitric oxide from placental explants cultured over a seven day period. Placental explants were maintained for seven days in culture and the medium was changed every 24 hours. The response was assessed in terms of syncytiotrophoblast differentiation (human chorionic gonadotropin, hCG), cellular cytolysis (lactate dehydrogenase, LDH), oxidative stress (thiobarbituric acid reactive substances, TBARS), and nitric oxide (NO). Levels of hCG increased progressively from day two to attain its highest level on days four and five after which it decreased gradually. In contrast, the levels of LDH, TBARS, and NO were elevated in the early days of placental culture when new syncytiotrophoblast from cytotrophoblast were forming and also in the last days of culture when tissue was declining. In conclusion, the levels of NO and lipid peroxidation follow a pattern similar to LDH and contrary to hCG. Future placental explant studies to evaluate oxidative stress and NO should consider the physiological changes inherent during the time of culture.

HLA-G5 induces IL-4 secretion critical for successful pregnancy through differential expression of ILT2 receptor on decidual CD4⁺ T cells and macrophages.

Successful pregnancy in humans has been associated with production of IL-4 by T cells at the feto-maternal interface. Soluble HLA-G5 produced by trophoblasts potentially controls the decidual T cell cytokine profile. We studied the effect of HLA-G5 on the cytokine profile of purified human macrophages and Ag-specific T cells in vitro. We demonstrated that HLA-G5 increased production of IL-12 by purified peripheral blood macrophages. Although IL-12 production by macrophages is known to induce IFN-γ production by CD4(+) T cells, HLA-G5 increased production of IL-4 but not IFN-γ by CD4(+) T cells after Ag presentation by macrophages. We found that this apparent paradox was due to the differential expression of the ILT2 HLA-G5 receptor on activated T cells and macrophages. This receptor was upregulated in the former and downregulated in the latter after Ag presentation and activation of both cell types. This observation was confirmed in situ, where decidual macrophages and T cells are continuously exposed to HLA-G5 produced locally and activated by trophoblast alloantigens. Freshly isolated decidua basalis macrophages expressed lower levels of ILT2 than peripheral blood macrophages from the same pregnant women. They did not spontaneously produce IL-12, whereas freshly isolated decidual CD4(+) T cells expressed high levels of activation markers (CD25, HLA-DR, and CD69) as well as ILT2 and spontaneously produced IL-4 but not IFN-γ. Therefore, HLA-G5 could be responsible, at least in part, via its interaction with ILT2, for decidual T cell IL-4 production, known to be crucial for successful pregnancy.

The human decidual NK-cell response to virus infection: what can we learn from circulating NK lymphocytes?

NK cells present in the peripheral blood respond rapidly to pathogens or pathogen-infected cells by various means including cytotoxicity and production of cytokines. Whether decidual NK (dNK) cells are able to play a similar role when the pregnant uterus is infected by viruses is still largely unknown. Decidual NK cells are generally considered as poorly cytotoxic when compared to their peripheral blood counterparts. However, we have recently demonstrated that freshly isolated dNK cells from healthy early pregnant uterus do have a cytotoxic potential mediated by the specific engagement of NKp46 activating receptor. We further found that the co-engagement of CD94/NKG2A inhibiting receptor drastically inhibits the cytolytic function of dNK. This latter observation suggests that in situ the CD94/NKG2A receptor interaction with its HLA-E specific ligand is a dominant negative regulatory mechanism that prevents unwanted dNK cell cytotoxicity in non-infected pregnant uterus. How do dNK cells behave when they are activated by virus-infected cells present at the maternal-fetal interface? Largely based on data obtained from circulating NK cells, this review briefly discusses the following questions: Does uterine viral infection promote decidual NK cell proliferative capacity in situ? Are dNK cells able to kill virus-infected autologous decidual target cells and thus limit the virus spreading to the fetus? Which viral-mediated signal(s) and molecular interactions may subvert inhibition of dNK cytotoxic potential? Does uterine viral infection promote decidual NK cell secretion of cytokines and chemokines that boost the anti-viral immune response?

Serum levels of interleukin-6, interleukin-1beta and human chorionic gonadotropin in pre-eclamptic and normal pregnancy.

Studies in placentas from the first trimester and in vitro models indicate that interleukin (IL)-1beta and IL-6 induce the release of human chorionic gonadotropin (hCG). During pre-eclampsia there is an increase of pro-inflammatory cytokines; however, its relationship with hCG levels during the third trimester of pregnancy has not been determined. The aim of the present study was to evaluate the relationship between blood levels of IL-6, IL-1beta and hCG in normal pregnancy and pre-eclampsia. Blood samples during the third trimester of pregnancy from women with severe pre-eclampsia (n = 20) or normal pregnancy (n = 20) were assayed for hCG by immunoassay, IL-6 and IL-1beta by enzyme-linked immunosorbent assay. Serum level of IL-6 was significantly higher in pre-eclamptic than in normal women (16.5 +/- 2.1 vs. 4.9 +/- 1.1 pg/ml); however, IL-1beta was similar in both groups. Although hCG was higher in pre-eclampsia than normal pregnancy, the difference was not statistically significant. Furthermore, IL-1beta in normal pregnancy was correlated negatively with hCG (r = -0.69, p < 0.001). In conclusion, serum levels of IL-6 were increased in pre-eclampsia but were not correlated with hCG or IL-1beta; however, in normal pregnancy there was a negative correlation between IL-1beta and hCG. The interaction between IL-1beta and hCG at the third trimester needs to be investigated.

Preeclampsia and calcium-ATPase activity of plasma membranes from human myometrium and placental trophoblast.

OBJECTIVE: We determined calcium-activated adenosine triphosphatase (Ca-ATPase) activity and thiobarbituric acid-reactive substances (TBARS) of plasma membranes from myometrium and placental trophoblast of normotensive and preeclamptic pregnant women. METHODS: Samples of myometrium were obtained by uterine biopsies taken upon delivery by cesarean section from nulliparous normotensive and preeclamptic pregnant women. Placentas were obtained after full term vaginal delivery from either normotensive or preeclamptic women. Plasma membrane fractions were prepared from both myometrium and placenta and assayed for Ca-ATPase activity and TBARS. MAIN OUTCOME MEASURE(S): We expected to find a higher level of TBARS and, consequently, a lower activity of Ca-ATPase of the plasma membrane fractions obtained from both myometrium and placenta of preeclamptic women. RESULTS: The Ca-ATPase activity of myometrium and placental trophoblast from preeclamptic women was about 50% lower than that from normotensive women, while the TBARS were higher. CONCLUSIONS: A reduced Ca-ATPase activity, caused by an increased level of TBARS, may result in an increase in the cytosolic calcium concentration in the vascular smooth muscle cells of preeclamptic women and thus partially explain the high blood pressure developed by these patients.

Bioactive to immunoreactive ratio of circulating human chorionic gonadotropin as possible evaluation for the prognosis of threatened abortion.

OBJECTIVE: In an effort to evaluate the prognosis of threatened abortion, we established the ratio of serum human chorionic gonadotropin (hCG), as measured by bioassay or radioimmunoassay techniques, of samples from patients with threatened abortion or normal pregnancy. STUDY DESIGN: Peripheral blood samples from patients in their first trimester of pregnancy with threatened abortion (n=24), or normal pregnancy (n=12), were assayed for progesterone (RIA), and for immunoactive (DELFIA) and bioactive (mouse Leydig cell testosterone production assay) hCG. RESULTS: Serum progesterone was not statistically different between the threatened-continuing and the threatened-miscarried groups. The ratio of hCG bioactive/hCG immunoactive (B/I) was significantly lower for the patients of the threatened group that experienced abortion. The B/I ratio for the control and threatened-continuing patients was similar. CONCLUSION: The hCG bioactive/hCG immunoactive ratio could be a good indicator of the prognosis of threatened abortion.