MD-1 is a critical part of the mechanism causing Th1-cytokine-triggered murine fetal loss syndrome

Decidual NR2F2-Expressing CD4+ T Cells Promote TH2 Transcriptional Program During Early Pregnancy

A unique immunotolerant microenvironment with Th2 bias in the decidua provides an essential security for successful pregnancy. The disorganized maternal-fetal immune tolerance contributes to more than 50% of unexplained recurrent spontaneous abortion (RSA). How the Th2 bias is developed at the maternal-fetal interface remains undefined. NR2F2, a member of steroid/thyroid nuclear receptor superfamily, is endowed with diverse importance in cell-fate specification, organogenesis, angiogenesis, and metabolism. Here, we showed that NR2F2 was absolutely highly expressed in decidual CD4⁺T(dCD4⁺T) cells, but not in peripheral circulating CD4⁺T cells during early pregnancy. Decidual NR2F2-expressing CD4⁺T cells dominantly produced Th2 cytokines. In unexplained RSA patients, NR2F2 expression in dCD4⁺T cells was significantly decreased, accompanied with disordered phenotype of dCD4⁺T cells. Furthermore, overexpression of NR2F2 promoted the Th2 differentiation of naive CD4⁺T cells. Immunoprecipitation experiment confirmed the binding relationship between GATA-3 and NR2F2, which implied GATA-3 may be an important interactive element involved in the immunoregulatory process of NR2F2. This study is the first to reveal a previously unappreciated role for NR2F2-mediated dCD4⁺T cells in maternal-fetal immune tolerance and maintenance of normal pregnancy, in the hope of providing a potential biomarker for prediction and prevention of clinical unexplained RSA.

CD200:CD200R Interactions and Their Importance in Immunoregulation

The molecule CD200, described many years ago as a naturally occurring immunomodulatory agent, capable of regulating inflammation and transplant rejection, has attracted additional interest over the past years with the realization that it may also serve as an important marker for progressive malignancy. A large body of evidence also supports the hypothesis that this molecule can contribute to immunoregulation of, among other diseases, infection, autoimmune disease and allergy. New data have also come to light to characterize the receptors for CD200 (CD200R) and their potential mechanism(s) of action at the biochemical level, as well as the description of a novel natural antagonist of CD200, lacking the NH₂-terminal region of the full-length molecule. Significant controversies exist concerning the relative importance of CD200 as a ligand for all reported CD200Rs. Nevertheless, some progress has been made in the identification of the structural constraints determining the interaction between CD200 and CD200R, and this information has in turn proved of use in developing novel small molecule agonists/antagonists of the interaction. The review below highlights many of these newer findings, and attempts to place them in the broad context of our understanding of the role of CD200-CD200R interactions in a variety of human diseases.

Regulatory B cells with IL-35 and IL-10 expression in a normal and abortion-prone murine pregnancy model

PROBLEM

Interleukin 35 is a relatively newly discovered cytokine that is produced by regulatory B cells (Bregs) and contributes to their suppressive function, which may contribute to fetal tolerance development and pregnancy maintenance. Therefore, the aim of this study was to determine the frequency of Bregs and expression of IL-35 and IL-10 in these cells in a normal and abortion-prone murine pregnancy model.

METHODS OF STUDY

The frequency of Bregs and expression level of IL-35 and IL-10 in these cells were measured in peripheral blood, uterine draining lymph nodes, uterus, and decidua using flow cytometry. The analysis was performed on days 3 and 14 of pregnancy in normal mice (CBA/JxBALB/c) and abortion-prone (CBA/JxDBA/2J) murine pregnancy model.

RESULTS

A decreased percentage of Breg cells expressing IL-35 on day 3 of pregnancy in the uterine draining lymph nodes and in peripheral blood in mice from the abortion group compared with the normal pregnancy group was observed. A similar decrease was also observed in the Breg cells population producing IL-10 in peripheral blood. In the uterus (3 dpc) and decidua (14 dpc), a lower percentage of CD19⁺ IL-35⁺ was also noted in the abortion-prone model.

CONCLUSION

We indicated that the early stages of abortion-prone pregnancy (3 dpc) in mice were characterized by diminished frequency of B cells producing IL-35 at both local and peripheral levels. These results and the observed lower level of IL-35 in women suffering from recurrent spontaneous abortion suggest that IL-35 may be involved in the maintenance of pregnancy.

Modulatory Mechanism of Polyphenols and Nrf2 Signaling Pathway in LPS Challenged Pregnancy Disorders

Early embryonic loss and adverse birth outcomes are the major reproductive disorders that affect both human and animals. The LPS induces inflammation by interacting with robust cellular mechanism which was considered as a plethora of numerous reproductive disorders such as fetal resorption, preterm birth, teratogenicity, intrauterine growth restriction, abortion, neural tube defects, fetal demise, and skeletal development retardation. LPS-triggered overproduction of free radicals leads to oxidative stress which mediates inflammation via stimulation of NF-κB and PPARγ transcription factors. Flavonoids, which exist in copious amounts in nature, possess a wide array of functions; their supplementation during pregnancy activates Nrf2 signaling pathway which encounters pregnancy disorders. It was further presumed that the development of strong antioxidant uterine environment during gestation can alleviate diseases which appear at adult stages. The purpose of this review is to focus on modulatory properties of flavonoids on oxidative stress-mediated pregnancy insult and abnormal outcomes and role of Nrf2 activation in pregnancy disorders. These findings would be helpful for providing new insights in ameliorating oxidative stress-induced pregnancy disorders.

Decoding the chemokine network that links leukocytes with decidual cells and the trophoblast during early implantation

Chemokine network is central to the innate and adaptive immunity and entails a variety of proteins and membrane receptors that control physiological processes such as wound healing, angiogenesis, embryo growth and development. During early pregnancy, the chemokine network coordinates not only the recruitment of different leukocyte populations to generate the maternal-placental interface, but also constitutes an additional checkpoint for tissue homeostasis maintenance. The normal switch from a pro-inflammatory to an anti-inflammatory predominant microenvironment characteristic of the post-implantation stage requires redundant immune tolerance circuits triggered by key master regulators. In this review we will focus on the recruitment and conditioning of maternal immune cells to the uterus at the early implantation period with special interest on high plasticity macrophages and dendritic cells and their ability to induce regulatory T cells. We will also point to putative immunomodulatory polypeptides involved in immune homeostasis maintenance at the maternal-placental interface.

To drive or be driven: the path of a mouse model of recurrent pregnancy loss

This review is an example of the use of an animal model to try to understand the immune biology of pregnancy. A well-known model of recurrent spontaneous pregnancy loss is put in clinical, historical, and theoretical context, with emphasis on T cell biology.

Seminal plasma peptides may determine maternal immune response that alters success or failure of pregnancy in the abortion-prone CBAxDBA/2 model

Spontaneous abortion (resorption) in the DBA/2-mated CBA/J mouse involves a deficiency in Treg cell activity against paternal antigens at the time of mating. Preimmunization of female CBA/J by BALB/c splenocytes, but not DBA/2 splenocytes, protects against subsequent abortions after a CBAxDBA/2 mating. Previous immunogenetic studies with BALB/cxDBA/2 recombinants have indicated that H-2(d)-restricted presentation of a single minor non-H-2(d) peptide might be responsible for protection, while the product of a second independent allele might promote abortions. Using brefeldin-treated BALB/c and DBA/2 splenocytes, we found that incubation in BALB/c seminal plasma rendered DBA/2 splenocytes protective and DBA/2 seminal plasma eliminated protection. The active protective moiety was <10 kD consistent with a peptide. DBA/2 seminal plasma contained a <10-kD peptide that boosted the abortion rate. Maternal H-2(k) CBA/J splenocytes were unable to present the protective activity. Amicon fractionation also unmasked a <10-kD activity in DBA/2 seminal plasma that could boost abortion rates when presented by BALB/c splenocytes. SELDI-TOF mass spectrometry proteomic analysis of <10-kD filtrates reproducibly detected 1416, 1468, 1774 D peptides in BALB/c that were reduced or absent in DBA/2, and the presence of 2662, 4559 and 5320 D molecules in DBA/2, the latter two definitely not present in BALB/c. Direct antigen presentation of paternal H-2(d)-restricted paternal peptides (600-1800 D) may prevent the rejection of the CBAxDBA/2 embryos, and larger sized peptides may bind to immunizing splenocytes and augment abortion mechanisms.

Tolerance induction at the early maternal-placental interface through selective cell recruitment and targeting by immune polypeptides

Pregnancy challenges immune cells and immunomodulatory circuits of the mother and the developing fetus to dynamically adapt to each other in an homeostatic and tolerant environment for fetal growth. This entails the coordination of multiple cellular processes all devoted to accommodate and nourish the fetus while protecting the mother from endogenous and exogenous threatens. From the earliest stages of pregnancy, several strategies to efficiently communicate immune and trophoblast cells within the interface or at a distance were identified and chemokines might act at on different targets through direct or indirect mechanisms. Here, we briefly review some mechanisms of T regulatory cell recruitment to the early maternal-placental interfaces to accomplish immunotolerance and homeostatic control and we discuss evidence on two locally released polypeptides, RANTES (regulated on activation, normal, T-cell expressed, and secreted) and vasoactive intestinal peptide (VIP), as novel contributors to the multiplicity of immune tolerant responses and uterine quiescence requirements.

Profiling Lgals9 splice variant expression at the fetal-maternal interface: implications in normal and pathological human pregnancy

Disruption of fetal-maternal tolerance mechanisms can contribute to pregnancy complications, including spontaneous abortion. Galectin-9 (LGALS9), a tandem repeat lectin associated with immune modulation, is expressed in the endometrium during the mid and late secretory phases and in decidua during human early pregnancy. However, the role of LGALS9 during pregnancy remains poorly understood. We used real-time PCR and immunohistochemical staining to analyze the expression of Lgals9/LGALS9 during mouse gestation as well as in human tissues obtained from normal pregnancy and spontaneous abortions. In mice, three Lgals9 splice variants were detected, the expression of which was differentially regulated during gestation. Furthermore, decidual Lgals9 expression was deregulated in a mouse model of spontaneous abortion, whereas placental levels did not change. We further found that the LGALS9 D5 isoform suppresses interferon gamma production by decidual natural killer cells. In human patients, six Lgals9 splice variants were detected, and a decrease in Lgals9 D5/10 was associated with spontaneous abortion. Altogether, these results show a differential regulation of Lgals9 isoform expression during normal and pathological pregnancies and designate Lgals9 as a potential marker for adverse pregnancy outcomes.

Regulatory T cells and reproduction: how do they do it?

Regulatory T cells (Treg cells) identified by expression of Foxp3 play an important role in successful implantation and gestation. Various mechanisms have been proposed to explain their actions, and the more credible and less credible are set out in this review. Induction of Treg cells is believed to occur in response to paternal antigens in seminal plasma at the time of mating, and these Treg cells home to the uterus prior to implantation. Tolerogenic dendritic cells are proposed to play an important role in the generation of Treg cells in the draining lymph nodes and in maintaining Treg activity in the uterus. Recent data indicate that abortion in the CBAxDBA/2 model may be prevented by seminal plasma antigens from DBA/2 and BALB/c males, but H-2(d) restriction suggests that presentation to Treg cells might occur via a novel mechanism. The relevance of findings in mice to human pregnancy problems is also discussed.

Neutralization of LPS or blockage of TLR4 signaling prevents stress-triggered fetal loss in murine pregnancy

Maternal stress can cause loss of both histocompatible (syngeneic) and histoincompatible (semiallogeneic) embryos in pregnant mice. Stress increases abortogenic Th1 cytokines and reduces levels of anti-abortogenic Th2 cytokines, progesterone levels, and T regulatory cell activity. While physiological levels of interferon-γ promote vascular remodeling at the feto-maternal interface, an overshooting Th1 cytokine response requires a Toll-like receptor (TLR)-mediated "danger signal" such as lipopolysaccharide (LPS). Interestingly, stress can enhance permeability of mucosal membranes to entry of bacterial products and promote transmucosal migration of commensal bacteria. We hypothesized that bacterial component such as LPS may provide the danger signal through which stress triggers maternal immune activation, subsequently resulting in fetal rejection. Blocking the TLR4 receptor for LPS or neutralization of LPS using bactericidal permeability increasing protein abrogate fetal loss due to sonic stress challenge in DBA/2J-mated CBA/J mice. These treatments prevented stress-triggered immune responses in the decidua, upregulated Treg cells, and reduced the frequency of mature dendritic cells in uterine-draining lymph nodes but not in the uterus. Interestingly, anti-TLR4 treatment only partly ameliorated stress-induced endocrine responses, such as increased hypothalamic corticotropin releasing hormone and vasopressin mRNA expression but not decrease of serum progesterone. Galectin-1 knock-out mice were more susceptible to stress-triggered complete implantation failure rather than fetal loss, which was also abolished by LPS neutralization. Insights provided in this paper shed new light on the mechanisms by which stress affects pregnancy outcome and introduce microbial-derived LPS as a mediator within the cascade of stress-triggered immune and endocrine events during pregnancy.

Ecology of danger-dependent cytokine-boosted spontaneous abortion in the CBA x DBA/2 mouse model: II. Fecal LPS levels in colonies with different basal abortion rates

PROBLEM

Previous data have shown that 'danger' signals, such as bacterial lipopolysaccharide (LPS) acting via toll-like receptors (TLR), are conditions antecedent to early pregnancy failure in several murine abortion models. Indeed, the abortion rate increased in the CBA x DBA/2 model after injection of tumor necrosis factor-alpha (TNF-alpha) + interferon (IFN-gamma) on gestation day (GD) 7.5 only if the LPS-TLR signaling pathway was intact. High rates of cytokine-boosted abortion >80% loss can be demonstrable in certain animal colonies that have a high endogenous (spontaneous) rate of resorption (30-50%). A specific role for LPS on GD 0.5 determines the endogenous loss rate and on GD 6.5 the responsiveness to cytokine boosting of losses. Th1 cytokines (or the stress that induces these cytokines) increase intestinal permeability and absorption of luminal contents. It was predicted that intestinal availability of LPS was a major factor in the endogenous and cytokine-boosted resorption rates.

METHOD OF STUDY

A fixed weight of fresh mouse droppings from CBA/J female mice house in a high-abortion-rate (30-40%) colony at Clamart, France was homogenized and filtered. Fresh mouse droppings from a low-abortion-rate (10-15%) colony in Berlin, Germany were similarly processed. LPS was assayed using the Limulus amoebocyte lysate bioassay.

RESULTS

To our surprise, there was no significant difference in LPS content of fecal samples from the two colonies.

CONCLUSION

A high endogenous rate of abortion and cytokine (or stress) boosted abortion in the CBA x DBA/2 model is not explained by the LPS content of feces. Possible explanations include: fecal LPS does not reflect small intestinal LPS, there are additional TLR signals besides LPS that are important and endogenous stress levels may be higher in high-abortion-rate colonies, so permeability of the intestine (and Th1 cytokine levels) may be already higher. These data have implications for studies on the role of flora in human pregnancy problems.

Role of TNF-α in human female reproduction

TNF-α is a highly versatile cytokine, playing an important role in both apoptosis and inflammation, which is central to reproduction. It belongs to the Th1 type of cytokines. Thus, TNF-α is a proinflammatory cytokine and is involved during follicle development and ovulation, corpus luteum formation and regression and cyclic endometrium function. It has been postulated to be detrimental to the survival of the conceptus due to apoptosis of human primary villous trophoblast cells, leading to miscarriage. However, TNF-α may have a dual role in early pregnancy. Hormonally regulated uterine TNF-α in the mother is probably essential for trophoblast cell invasion, while increased production of TNF-α by maternal macrophages may facilitate labor. The current knowledge on the role of TNF-α and its receptors in the female reproduction is described in this review.

LPS-induced murine abortions require C5 but not C3, and are prevented by upregulating expression of the CD200 tolerance signaling molecule

PROBLEM

Lipopolysaccharide (LPS) acts via tlr4 to promote Th1 cytokine secretion and abortions. LPS is an essential co-factor in spontaneous abortion in the CBA x DBA/2 model and in stress-triggered abortions. In the CBA x DBA/2 model, C3a, C5a, and fgl2 prothrombinase participate in triggering inflammation that terminates embryo viability. As fgl2 prothrombinase (via thrombin) can generate C5a, it was predicted that LPS-driven abortions (which require fgl2) would be independent of C3. CD200Fc can prevent abortions in the CBA x DBA/2 model, but an action through Fc could not be excluded.

METHOD OF STUDY

C3(-/-) and C5(-/-) knock-out mice on a B6 background were syngeneically mated and Salmonella enteritidis LPS was administered i.p. on day 6.5 or pregnancy along with 2 mg progesterone in sesame oil s.c. The total number of implants and the number of resorbing embryos were counted on day 13.5 of pregnancy. CD200-rtTA double transgenic homozygous males (B6 background) mated with B6(+/+) females were similarly treated. To up-regulate CD200 expression in embryonic trophoblasts, doxycycline was added to the drinking water from the time of mating.

RESULTS

The LPS boosted the abortion rate from 15.5% (control) to 42.0% in C3(-/-) mice (chi(2) = 9.28, P < 0.005). In C5(-/-) mice, there was no increase in abortion rate with LPS compared to progesterone-treated controls (22.8%versus 26.3%, P = NS). LPS-treated transgenic mice given LPS + progesterone had a 42.5% abortion rate, but when the mice were given doxycycline to induce expression of CD200 by the embryo, the abortion rate was only 8.3% (chi(2) = 14.40, P < 0.005, Fisher's exact test P = 0.00007).

CONCLUSION

C5, but not C3, appears necessary for LPS-driven abortions. Up-regulation of CD200 can prevent LPS-driven abortions, possibly by altering dendritic cells to promote Treg cell development or by a direct suppressive action on macrophages and mast cells that also express CD200 receptors.

LPS-induced occult loss in mice requires FGL2

PROBLEM

FGL2 prothrombinase is required for spontaneous abortion (resorptions) in the CBA x DBA/2 model, and for abortions in C57Bl/6 (B6) mice triggered by Salmonella enteritidis lipopolysaccharide (LPS). Unlike abortions, occult losses in B6 mice, which begin before gestation day 9.5 in mice, do not require the tumor necrosis factor-alpha receptor type 1, and may be triggered by either Salmonella enteritidis or Escherichia coli LPS. Heterozygous matings of fgl2+/-xfgl2+/- B6 mice also have a high spontaneous occult loss of fgl2-/- and to a lesser extent, fgl2+/- embryos caused by hemorrhage between trophoblast and Reichert's membrane. However, the frequency of such losses appears to vary among breeding periods and between laboratories.

METHOD OF STUDY

We tested the hypothesis that FGL2-deficient embryos were uniquely susceptible to LPS by treating B6 fgl2+/-xfgl2+/- heterozygous matings with 2 microg E. coli LPS intraperitoneally on day 6.5 of pregnancy. Progesterone 2 mg in 100 microL sesame oil was administered subcutaneously at the same time to ensure that the effects of the LPS were not because of suppression of ovarian hormone production. PCR DNA genotyping was performed on embryos at day 13.5 of pregnancy, or after parturition.

RESULTS

Surprisingly, we found that LPS caused occult loss of fgl2+/+, and to a lesser extent fgl2+/- embryos, both at term and by PCR typing of embryos at gestation day 13.5, and these losses obscured the effect of fgl2 knockout.

CONCLUSION

Spontaneous loss of fgl2-/- embryos may relate to adhesion effects, whereas fgl2+/+ embryos are susceptible to LPS-induced loss; fgl2+/- embryos may be affected by both mechanisms. Antagonizing FGL2 could prevent occult pregnancy loss in some human and animal situations.

Transfusion-related immunomodulation due to peripheral blood dendritic cells expressing the CD200 tolerance signaling molecule and alloantigen

BACKGROUND

The transfusion of allogeneic blood products containing white cells (WBCs) has been reported to reduce resistance to infection, stimulate the growth of some types of tumors in animal models, and prevent abortion of allogeneic embryos in the CBAxDBA/2 murine model.

STUDY DESIGN AND METHODS

In this study, the issue explored was whether allogeneic BALB/c whole blood given to C57Bl/6 mice by tail vein after injection of syngeneic FSL-10 fibrosarcoma cells increased the number of lung nodules enumerated on Day 21. The effect on the tumor growth-promoting effect produced by allogeneic BALB/c whole blood was then examined by exposure of the allogeneic BALB/c blood to various monoclonal antibodies (MoAbs). The antibodies added to the BALB/c blood included anti-murine CD200 antibodies, anti-lymphoid dendritic cell (DC) antibodies (DEC205), or anti-myeloid DC (anti-CD11c) antibodies.

RESULTS

The tumor growth-promoting effect of the allogeneic BALB/c blood was abrogated by the addition to the BALB/c blood of MoAb either to myeloid DCs (anti-CD11c) or to the CD200 tolerance signaling molecule, but not by adding MoAb to lymphoid DCs (DEC205). BALB/c blood also was shown to increase the percentage of transforming growth factor (TGF)-beta+ splenocytes detected in recipient mice, on Day 12 after transfusion. This effect was abrogated by adding anti-CD200 antibody to the BALB/c donor blood. Moreover, physiologic concentrations of TGF-beta, but not interleukin-10, were shown to stimulate, in cell culture experiments, the proliferation of syngeneic FSL-10 sarcoma cells.

CONCLUSIONS

These data support the hypothesis that the mechanism of the tumor growth-promoting effect of allogeneic blood is mediated by a highly potent population of peripheral blood DCs expressing the CD200 tolerance signaling molecule. These data also indicate that tumor cell growth can be mediated by the stimulation of TGF-beta-producing cells and that TGF-beta may act by tumor cell growth stimulation, rather than by host immunosuppression.

Cytokines: Important for implantation?

PROBLEM

Cytokines are obviously very important in an established pregnancy, but what about human embryo implantation?

METHODS

Literature review.

RESULTS

We first discuss the necessity and limits of animal models, and then review the few cytokines which have been demonstrated by knock-out methods to be absolutely necessary for embryo implantation using in animal models. We then review what is known or discussed about the role of other cytokines as deduced from quantitative and/or qualitative dysregulation in animals and in humans.

CONCLUSIONS

Cytokines are indeed involved in implantation as they are in ongoing pregnancy and delivery. Relevance to infertility and recurrent pregnancy loss is discussed.

Toll-like receptor 4 polymorphisms and idiopathic chromosomally normal miscarriage

BACKGROUND

Lipopolysaccharide (LPS or endotoxin) exposure resulting from microbial invasion of the endometrium disturbs the Th1/Th2 balance at the feto-maternal interface and has been linked to the risk of idiopathic miscarriage in a range of human and animal studies. Toll-like receptor 4 (TLR4) mediates LPS signalling, and the human TLR4 gene harbours two single-nucleotide polymorphisms (SNPs) known to reduce LPS responsiveness. We hypothesized that genetic variation altering TLR4 function may influence the risk of idiopathic pregnancy loss.

METHODS AND RESULTS

We examined fetal TLR4 genotypes in a case-control cohort of chromosomally normal miscarriages (n=96) and healthy term newborns (n=113). The allele frequencies of the Asp299Gly and Thr399Ile TLR4 SNPs were determined by quantitative PCR using DNA extracted from extraembryonic tissues and umbilical cord blood, respectively. TLR4 genotype frequencies were not significantly different between cases and controls.

CONCLUSIONS

There was no association between fetal TLR4 polymorphisms, Asp299Gly and Thr399Ile, known to blunt LPS responsiveness, and the risk of idiopathic, chromosomally normal miscarriage. Nevertheless, TLR4 or perhaps other LPS-binding chaperone molecules are biologically plausible candidate genes that may alter the risk of idiopathic miscarriage.

Reduced uterine indoleamine 2,3-dioxygenase versus increased Th1/Th2 cytokine ratios as a basis for occult and clinical pregnancy failure in mice and humans

PROBLEM

Indoleamine 2,3-dioxygenase (IDO) expression in fetal trophoblast and decidual antigen-presenting cells has been proposed to inactivate maternal T cells and thereby prevent rejection of the "fetal allograft" in early pregnancy. Psychic stress has been proposed to cause miscarriages as well as infertility, at the same time in pregnancy when blockade of IDO causes loss, but the suggested mechanism of stress-triggered loss has been an increased ratio of pro-rejection Th1-type cytokines to anti-rejection Th2/3 cytokines. Could stress act by reducing IDO expression?

METHODS

Using DBA/2-mated A/J mice where stress causes early pregnancy failure, we examined the role of stress in reducing IDO versus increasing Th1/Th2 ratio in deciduas. IDO loss was also examined in human decidua associated with pregnancy failure.

RESULTS

A post-implantation sonic stress increased the pregnancy failure rate, increased the Th1/Th2 ratio, but did not reduce IDO. IDO was reduced, and Th1/Th2 ratios increased in A/J mice pre-immunized against paternal DBA/2 antigens, and concomitant stress increased these effects. The rate of pregnancy failure was not further increased consistent with recent discoveries of factors that limit the impact of Th1 cytokines at the feto-maternal interface. In deciduas from spontaneous miscarriage patients, IDO(+) cell frequencies were low in only 30% of patients. CD3(+) T-cell numbers and percentage terminal deoxynucleotidyl transferase (TdT)-mediated dUTP-digoxigenin nick end-labelling (TUNEL)(+) apoptotic T cells were increased, but the level of IDO did not correlate with likelihood of apoptosis.

CONCLUSIONS

Loss of an allogeneic embryo in early pregnancy is more likely to be due to a high Th1/Th2 ratio than loss of putative protection by IDO.

Is intravenous immunoglobulins (IVIG) efficacious in early pregnancy failure? A critical review and meta-analysis for patients who fail in vitro fertilization and embryo transfer (IVF)

PROBLEM

Intravenous Immunoglobulins (IVIG) are widely used off label in the treatment of early reproductive failure. As IVIG is expensive, and may have side-effects, evidence of efficacy is needed. Previous results have suggested that the pre-conception treatment of primary recurrent abortion patients might be effective, but the data set has been too small for adequate statistical power. More recently it has been suggested that IVIG may improve the success rate of in vitro fertilization and embryo transfer (IVF) in patients with prior IVF failures, but clinical trials have given conflicting results that need explanation. Systematic reviews generating inconclusive results have focused on methodological rigor to the exclusion of biological plausibility.

METHODS

Review of current basic science of design, measurement, and evaluation of clinical trials and basic science mechanisms providing a rationale for treatment. Meta-analysis of published randomized controlled and cohort-controlled trials (updated with two unpublished data sets) evaluating IVIG treatment in IVF failure patients. Live birth rate was used as the most relevant endpoint. The ability of different sources of IVIG to suppress natural killer (NK) cell activity was determined using a standard (51)Cr-release assay in vitro.

RESULTS AND CONCLUSIONS

Meta-analysis of three published randomized controlled trials (RCTs) of IVIG in IVF failure patients shows a significant increase in the live birth rate per woman (p = 0.012; Number Needed to Treat for 1 additional live birth, NNT = 6.0 women). Using live birth rate per embryo transferred, and adding data from two cohort-controlled trials to the meta-analysis further supports this conclusion (overall p = 0.000015, NNT = 3.7 women). Relevant variables appear to include properties and scheduling of the IVIG, and selection of patients with abnormal immune test results. Different IVIG preparations vary significantly in their ability to suppress NK activity in vitro. A rationale for use of IVIG is provided by a review of mechanisms of IVIG action and mechanisms underlying failure of chromosomally normal embryos.

Is the CD200/CD200 receptor interaction more than just a myeloid cell inhibitory signal?

The membrane glycoprotein CD200, which has a widespread but defined distribution and a structurally similar receptor (CD200R) that transmits an inhibitory signal to cells of the hematopoetic lineage, especially myeloid cells, has been characterized. CD200R expression is restricted predominantly to cells of the myeloid lineage indicating that this ligand/receptor pair has a specific role in controlling myeloid cell function. In addition to CD200R, several related genes have been identified. Whether these gene products also regulate immune function is controversial. CD200R is also expressed by certain subsets of T cells and CD200 may be expressed by antigen-presenting cells, adding additional layers of complexity to the CD200/CD200R axis. Because monocytic myeloid cells provide a link between the innate and adaptive immune response, mechanisms to control their function through receptors such as CD200R will have therapeutic potential. Regulation of immune responses is accomplished by the concerted, but opposing, activity of kinases and phosphatases, fine control often being achieved through paired receptors. In this review, we will consider whether CD200R signaling functions within a framework of paired activating and inhibitory receptors and whether the inhibitory signal delivered has functional consequences beyond inhibition of myeloid cell proinflammatory activation.

Maternal treatment with a high dose of CpG ODN during gestation alters fetal craniofacial and distal limb development in C57BL/6 mice

Synthetic oligodeoxynucleotides (ODN) containing CpG motifs, characteristic of bacterial DNA, are currently being evaluated as vaccine adjuvants for inducing protective immunity. Recently, there is increasing pressure to vaccinate pregnant women against maternally transmitted diseases including AIDS and tetanus, as well as against potential bio-weapons such as anthrax. CpG vaccines are effective because they trigger transient increases in T(H)1 cytokine production. Recent literature suggests, however, that a shift toward a T(H)1 cytokine profile during pregnancy may increase the risk of fetal morphologic defects. On this basis, we hypothesized that exposure to CpG motifs during pregnancy could result in T(H)1 inflammation leading to adverse effects on fetal development. To address this hypothesis, pregnant C57BL/6 mice were injected with CpG ODN (0-300 microg/dam) and maternal and fetal outcomes were determined. Injection of dams with the highest dose of CpG ODN resulted in markedly increased fetal resorptions and craniofacial/limb defects, while lower doses had little, if any effects. Histological examination of placentas revealed cellular necrosis with mixed inflammation and calcification in the spongiotrophoblast layer and dysregulation of labyrinthine vascular development. Concomitant elevations in maternal serum cytokine levels were observed including interleukin (IL)-2, IL-10 and IL-12. Treatment with 300 microg of non-CpG ODN did not cause any adverse effects. The 300 microg dose of CpG ODN used in the present study is 30-fold higher than the highest dose that has been administered to humans during clinical trials. These results suggest that the induction of T(H)1 cytokines during pregnancy by CpG motifs may potentially increase the risk of fetal loss and morphologic defects in mice, at least at high doses, and support the need for further investigation of teratogenesis that may result from exposure to vaccine adjuvants designed to produce T(H)1 cytokine profile shifts.

Effect of bacterial virulence on IL-18 expression in the amnion infected with Escherichia coli

PROBLEM

The upregulation of inflammatory substances threatens pregnancy. Interleukin-18 (IL-18) is elevated in women who miscarried. The purpose of this study was to develop a pig model of chorioamnionitis to study the effect of bacterial virulence on IL-18 response in experimentally infected amnion.

METHOD OF STUDY

A total of 20,000 colony-forming units of Escherichia coli (an enteropathogenic O55 strain, EPEC or O86 non-pathogenic strain) were administered into the amniotic cavity of pig fetuses at 70% of gestation for 10 hr. Fetal amniotic fluid samples were analyzed for IL-18 levels by enzyme-linked immunosorbent assay. The expression of IL-18 was studied also by immunohistochemistry on cryostat sections through amniotic membranes and pathological changes were observed by electron microscopy.

RESULTS

Both E. coli strains propagated in amniotic fluids and reached similar counts. Only EPEC, however, caused a significant increase of IL-18 amniotic fluid levels (P < 0.001) and cytokine expression in the amniotic epithelium.

CONCLUSIONS

The levels of IL-18 in infected amniotic fluids correlated with bacterial virulence and pathological changes in the amnion.

Phagocytosis as a potential mechanism for microbial defense of mouse placental trophoblast cells

Trophoblast giant cells are active phagocytes during implantation and post-implantation. Phagocytosis decreases during placental maturation as the phagocytic function of nutrition is gradually replaced by the direct uptake of nutrients by the labyrinth zone trophoblast. We hypothesize that, after placental maturation, trophoblast cells maintain phagocytic functions for purposes other than nutrition. This study employs histological techniques to examine the ability of trophoblast cells to phagocytose microorganisms (yeast or bacteria)--in vivo in females receiving thioglycolate to activate macrophages and in vitro in the presence of phagocytic promoters such as interferon-gamma and complement component C3. Placental trophoblast cells from the second half of gestation show basal phagocytosis that can be dramatically up-regulated by these promoters when microorganisms are inoculated into pregnant animals or introduced into culture systems. Stimulated trophoblast cells phagocytosed organisms more rapidly and in greater numbers than non-stimulated trophoblast exposed to the same numbers of organisms. Taken together, our results indicate that trophoblast cells do not lose their ability to phagocytose during the placentation process, which may imply that trophoblast cells participate in embryonic and fetal innate immune defense through elimination of microorganisms present at the maternal-fetal interface.

Ecology of Danger-dependent Cytokine-boosted Spontaneous Abortion in the CBA × DBA/2 Mouse Model. I. Synergistic Effect of LPS and (TNF-α + IFN-γ) on Pregnancy Loss

PROBLEM

Previous data have shown "danger" signals, such as bacterial lipopolysaccharide (LPS) acting via toll-like (tlr) receptors are required for early pregnancy failure in several murine abortion models. Indeed, the abortion rate increased in the CBA x DBA/2 model after a gestation day (gd) 7.5 injection of tumour necrosis factor (TNF)-alpha + interferon (IFN)-gamma only if the LPS-tlr signalling pathway was intact. High rates of cytokine-boosted abortion >80% loss can be achieved in certain animal colonies, that have a high endogenous (spontaneous) rate of resorption (30-50%). A specific role for LPS has been postulated to determine both the endogenous and cytokine-boosted losses.

METHODS

To test the role of LPS in spontaneous and cytokine-boosted abortions, recombinant TNF-alpha + IFN-gamma, and LPS were injected in different doses and sequences intraperitoneally (i.p.) into CBA x DBA/2 mated mice in the Toronto General Research Institute animal facility where the endogenous abortion rate is <30%. The effects of poly IC, a tlr3 agonist that induces IFN-gamma that can reverse LPS-induced tolerance, and effects of anti-MD-1 on TNF-alpha induction by LPS, poly IC, CPG, or HSP in vitro were also examined.

RESULTS

A high endogenous rate of loss similar to that seen in Clamart could be achieved by increasing exposure to LPS on the morning after mating (gd 0.5). The magnitude by which the abortion rate could be increased by an i.p. injection of 2000 u TNF-alpha + 1000 u IFN-gamma on gd 7.5 was independent of the endogenous rate of loss, and could not be increased by doubling the dose. One microgram of LPS given on day 7.5 achieved a similar rate of loss, and if given with the cytokines, synergistically boosted the rate of loss to near Clamart rates. LPS given 1 day prior to the cytokines abrogated the cytokine effect, whereas LPS given day 0.5 had no significant effect on the response to day 7.5 cytokine injection. Blocking MD-1 inhibited TNF-alpha stimulation by poly IC, LPS, CPG, or HSP in vitro, and reduced abortion rates. Poly IC did not avert LPS-type tolerance effects in vivo.

CONCLUSIONS

High endogenous rates of abortion in the CBA x DBA/2 model may be explained by exposure to LPS at the time of mating. Increased rates of loss triggered by cytokines later in pregnancy may depend on increased absorption of LPS from intestinal flora.

Shall We properly Re-examine the Status of Allogeneic Lymphocyte Therapy for Recurrent early Pregnancy Failure?

PROBLEM

How to evaluate immunological therapy advocated for recurrent spontaneous abortion and implantation failure. I was invited to comment on the opinion article of Chaouat (AJRI December 2003).

METHODS

A critical examination of key beliefs and application of the principles of evidence and logic utilizing current data.

RESULTS AND CONCLUSIONS

Although rationale has no bearing on efficacy of proposed treatments and is not sufficient justification for routine practice, insufficient attention to data concerning patient selection, insufficient attention to treatment methodology, and lack of full disclosure in some clinical trials needs to be corrected. A more systematic collection of follow-up data is needed.