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

The Predictive Significance of Platelet-to-Lymphocyte Ratio for Miscarriage: A Systematic Review and Meta-Analysis

BACKGROUND

Miscarriage is a common complication of pregnancy, and its underlying pathophysiologic mechanisms remains unclear. The platelet-to-lymphocyte ratio (PLR), a prothrombotic and inflammatory marker, has been controversially discussed as a potential predictor of miscarriage. This systematic review and meta-analysis aimed to assess the predictive significance of the PLR in women with miscarriage compared to healthy pregnancies.

MATERIAL AND METHODS

Relevant studies were systematically searched in PubMed, Embase, Web of Sciencey, and Cochrane Library up to December 31, 2023. A systematic review and meta-analysis following PRISMA guidelines was conducted. Articles were identified, screened, and evaluated for quality to determine the predictive value of PLR for miscarriage.

RESULTS

Fourteen eligible articles, comprising a total of 3745 patients, were included in the meta-analysis. The pooled analysis found comparable PLR levels between miscarriage and non-miscarriage groups (SMD = 0.25; 95% Confidence Interval (CI): -0.05 to 0.54). Subgroup analysis revealed significant differences in PLR levels in the missed miscarriage group (SMD = 0.29; 95% CI: 0.01-0.56). and in studies with sample sizes smaller than 200 (SMD = 0.31; 95% CI: 0.05-0.56). Other subgroups did not exhibit significant differences. Subgroup analysis of PLR levels and miscarriage risk demonstrated no significant differences across all subgroups.

CONCLUSION

PLR is not a reliable predictor of miscarriage in general. However, for missed miscarriage cases, elevated PLR levels may serve as a practical and cost-effective marker for prediction.

Cytokine and chemokine profiles in women with endometriosis, polycystic ovary syndrome, and unexplained infertility

Numerous factors (including immunological, congenital, hormonal, and morphological disorders) can lead to infertility. In this regard, 3 specific diseases associated with infertility are discussed in this review study (i.e., polycystic ovary syndrome [PCOS], endometriosis [EMS], and unexplained infertility [UI]). PCOS is a common endocrine disorder characterized by chronic low-grade inflammation, and EMS is a benign disease characterized by the presence of ectopic endometrial tissue. UI refers to couples who are unable to conceive for no known reason. Conception and pregnancy are significantly affected by the immune system; in this regard, chemokines and cytokines play important roles in the regulation of immune responses. Patients with PCOS, EMS, and UI have altered cytokine and chemokine profiles, suggesting that dysregulation of these molecules may contribute to infertility in these conditions. Accordingly, the issue of infertility is addressed in this review study, a condition that affects approximately 16% of couples worldwide.

Indoleamine 2, 3-dioxygenase 1 mediated alterations in the functionality of immune cells, deciphers the pregnancy outcomes in crossbred dairy cows

Pregnancy establishment in bovines requires maternal immune cell modulation. Present study investigated possible role of immunosuppressive indolamine-2, 3-dioxygenase 1 (IDO1) enzyme in the alteration of neutrophil (NEUT) and peripheral blood mononuclear cells (PBMCs) functionality of crossbred cows. Blood was collected from non-pregnant (NP) and pregnant (P) cows, followed by isolation of NEUT and PBMCs. Plasma pro-inflammatory (IFNγ and TNFα) and anti-inflammatory cytokines (IL-4 and IL-10) were estimated by ELISA and analysis of IDO1 gene in NEUT and PBMCs by RT-qPCR. Neutrophil functionality was assessed by chemotaxis, measuring activity of myeloperoxidase and β-D glucuronidase enzyme and evaluating nitric oxide production. Changes in PBMCs functionality was determined by transcriptional expression of pro-inflammatory (IFNγ, TNFα) and anti-inflammatory cytokine (IL-4, IL-10, TGFβ1) genes. Significantly elevated (P < 0.05) anti-inflammatory cytokines, increased IDO1 expression, reduced NEUT velocity, MPO activity and NO production observed only in P cows. Significantly higher (P < 0.05) expression of anti-inflammatory cytokines and TNFα genes were observed in PBMCs. Study highlights possible role of IDO1 in modulating the immune cell and cytokine activity during early pregnancy and may be targeted as early pregnancy biomarkers.

Does Altered Cellular Metabolism Underpin the Normal Changes to the Maternal Immune System during Pregnancy?

Pregnancy is characterised by metabolic changes that occur to support the growth and development of the fetus over the course of gestation. These metabolic changes can be classified into two distinct phases: an initial anabolic phase to prepare an adequate store of substrates and energy which are then broken down and used during a catabolic phase to meet the energetic demands of the mother, placenta and fetus. Dynamic readjustment of immune homeostasis is also a feature of pregnancy and is likely linked to the changes in energy substrate utilisation at this time. As cellular metabolism is increasingly recognised as a key determinant of immune cell phenotype and function, we consider how changes in maternal metabolism might contribute to T cell plasticity during pregnancy.

Decidual IDO+ macrophage promotes the proliferation and restricts the apoptosis of trophoblasts

Indoleamine 2, 3-dioxygenase (IDO), a tryptophan-catabolizing enzyme, is essential in physiological immunoregulation. The present research was conducted to elucidate the expression and roles of IDO in decidual macrophages (dMφ) during early pregnancy. Here, we observed a remarkable decrease of IDO⁺ dMφ from patients with unexplained recurrent spontaneous abortion (URSA). IDO⁺ dMφ displayed M2 phenotype with higher CD206, CD209 and CD163, and lower CD86. Interestingly, treatment with 1-methyl-d-tryptophan (1-MT, an IDO pathway inhibitor) led to the M1 bias of dMφ. Further analysis of the cytokine array and the qPCR showed decreased levels of trophoblast proliferation or invasion-related molecules (e.g., CXCL12 and BMP2) in 1-MT-treated dMφ. The data of co-culture system showed that 1-MT-pretreated dMφ decreased the proliferation and the expression of Ki-67 and Bcl-2, and increased cell apoptosis of HTR-8/Snveo cells. Additionally, the expression of IDO in U937 cells was up-regulated by decidual stromal cells (DSC) and HTR-8/Snveo cells in vitro, as well as estradiol and medroxyprogesterone. These data suggest that endocrine environment, DSC and trophoblasts should contribute to the high level of IDO in dMφ, and IDO⁺ dMφ with M2 dominant phenotype promote the survival of trophoblasts during early pregnancy. The abnormal lower level of IDO should trigger the dysfunction of dMφ, further suppress the survival of trophoblasts and increase the risk of miscarriage.

Analysis of Structural Variants Reveal Novel Selective Regions in the Genome of Meishan Pigs by Whole Genome Sequencing

Structural variants (SVs) represent essential forms of genetic variation, and they are associated with various phenotypic traits in a wide range of important livestock species. However, the distribution of SVs in the pig genome has not been fully characterized, and the function of SVs in the economic traits of pig has rarely been studied, especially for most domestic pig breeds. Meishan pig is one of the most famous Chinese domestic pig breeds, with excellent reproductive performance. Here, to explore the genome characters of Meishan pig, we construct an SV map of porcine using whole-genome sequencing data and report 33,698 SVs in 305 individuals of 55 globally distributed pig breeds. We perform selective signature analysis using these SVs, and a number of candidate variants are successfully identified. Especially for the Meishan pig, 64 novel significant selection regions are detected in its genome. A 140-bp deletion in the Indoleamine 2,3-Dioxygenase 2 (IDO2) gene, is shown to be associated with reproduction traits in Meishan pig. In addition, we detect two duplications only existing in Meishan pig. Moreover, the two duplications are separately located in cytochrome P450 family 2 subfamily J member 2 (CYP2J2) gene and phospholipase A2 group IVA (PLA2G4A) gene, which are related to the reproduction trait. Our study provides new insights into the role of selection in SVs' evolution and how SVs contribute to phenotypic variation in pigs.

Definition and Multiple Factors of Recurrent Spontaneous Abortion

Recurrent spontaneous abortion (RSA) is usually defined as three or more spontaneous abortions prior to 20-28 weeks gestation. RSA affects approximately 2-5% of all women of childbearing age, and it brings tremendous psychological and psychiatric trauma to the women and also results in economic burden. The causes could be female age, anatomical and chromosomal abnormalities, genetic, endocrinological, placental anomalies, infection, smoking and alcohol consumption, psychological factor, exposure to environmental factors such as heavy metal, environment pollution, and radiation.

The Ups and Downs of Metabolism during the Lifespan of a T Cell

Understanding the various mechanisms that govern the development, activation, differentiation, and functions of T cells is crucial as it could provide opportunities for therapeutic interventions to disrupt immune pathogenesis. Immunometabolism is one such area that has garnered significant interest in the recent past as it has become apparent that cellular metabolism is highly dynamic and has a tremendous impact on the ability of T cells to grow, activate, and differentiate. In each phase of the lifespan of a T-cell, cellular metabolism has to be tailored to match the specific functional requirements of that phase. Resting T cells rely on energy-efficient oxidative metabolism but rapidly shift to a highly glycolytic metabolism upon activation in order to meet the bioenergetically demanding process of growth and proliferation. However, upon antigen clearance, T cells return to a more quiescent oxidative metabolism to support T cell memory generation. In addition, each helper T cell subset engages distinct metabolic pathways to support their functional needs. In this review, we provide an overview of the metabolic changes that occur during the lifespan of a T cell and discuss several important studies that provide insights into the regulation of the metabolic landscape of T cells and how they impact T cell development and function.

Implantation associated changes in expression profile of indoleamine-2, 3-dioxygenase 1, Th1-Th2 cytokines and interferon-stimulated genes on neutrophils and peripheral blood mononuclear cells of crossbred cows

Effective bidirectional communication between the embryo and dam improves the reproductive efficiency of dairy cows. Possible role of immunosuppressive indolamine-2, 3-dioxygenase 1 (IDO1) enzyme in the regulation of maternal systemic cytokine balance/shift during early pregnancy establishment along with various interferon-stimulated genes (ISGs) expression in neutrophils and peripheral blood mononuclear cell (PBMCs) were investigated in crossbred cows. Blood was collected on days 0 i.e. day of Artificial Insemination (AI), 10, 18 and 36 post-AI followed by isolation of neutrophils and PBMCs for gene expression study of IDO1, anti-inflammatory cytokines (IL-4, IL-10 and TGFβ1), pro-inflammatory cytokines (IFNγ and TNFα) and ISGs (ISG15, MX1, MX2, OAS1) in pregnant and non-pregnant cows. Cows were grouped as pregnant and non-pregnant after pregnancy confirmation by non-return to heat, ultrasonography, per rectal examination along with progesterone and IFNτ assay. Significantly (P < 0.05) higher relative mRNA expression of IDO1 and anti-inflammatory cytokines on days 10 and 18 post-AI were observed in both neutrophils and PBMCs of pregnant cows. Pregnant cows showed significantly (P < 0.05) higher mRNA transcripts of IFNγ and TNFα genes on days 18 post-AI in both neutrophils and PBMCs. Expression of ISGs was higher (P < 0.05) on day 10^th and 18^th post AI in both the neutrophils and PBMCs of pregnant cows. The study indicates that systemic immune regulation by IDO1 (through cytokine shift) and ISGs in peripheral immune cells are essential for the establishment of pregnancy and may be targeted in future as biomarkers for pregnancy diagnosis.

Mechanism of indoleamine 2, 3-dioxygenase inhibiting cardiac allograft rejection in mice

Indoleamine 2, 3‐dioxygenase (IDO)‐mediated regulation of tryptophan metabolism plays an important role in immune tolerance in transplantation, but it has not been elucidated which mechanism specifically induces the occurrence of immune tolerance. Our study revealed that IDO exerts immunosuppressive effects through two pathways in mouse heart transplantation, ‘tryptophan depletion’ and ‘tryptophan metabolite accumulation’. The synergism between IDO⁺DC and TC (tryptophan catabolic products) has stronger inhibitory effects on T lymphocyte proliferation and mouse heart transplant rejection than the two intervention factors alone, and significantly prolong the survival time of donor‐derived transplanted skin. This work demonstrates that the combination of IDO⁺DC and TC can induce immune tolerance to a greater extent, and reduce the rejection of transplanted organs.

The Metabolic Requirements of Th2 Cell Differentiation

Upon activation, naïve CD4⁺ T cells differentiate into a number of specialized T helper (Th) cell subsets. Th2 cells are central players in immunity to helminths and are implicated in mediating the inflammatory pathology associated with allergies. The differentiation of Th2 cells is dependent on transcription factors such as GATA3 and STAT6, which prime Th2 cells for the secretion of interleukin- (IL-) 4, IL-5, and IL-13. Several lines of work now suggest that differentiating Th2 cells in the lymph node are potent IL-4 cytokine producers, but do not become competent IL-5- and IL-13-producing cells until after receiving cues from non-lymphoid tissue. It is evident that Th2 cells that enter tissues undergo considerable changes in chromatin architecture and gene expression, and that over this time, the metabolic requirements of these cells change considerably. Herein, we discuss the metabolic requirements of Th2 cells during their early and late differentiation, focusing on the impact of glucose and lipid metabolism, mTOR activation, the nuclear receptor PPAR-γ and several metabolites.

Biomarkers of preconception stress and the incidence of pregnancy loss

STUDY QUESTION

Are biomarkers of preconception stress associated with pregnancy loss?

SUMMARY ANSWER

Preconception stress, as measured by basal salivary cortisol and alpha-amylase concentrations, is not associated with pregnancy loss.

WHAT IS KNOWN ALREADY

Many studies, most of which have been retrospective, have identified an association between stressful life events and perceived stress and miscarriage.

STUDY DESIGN, SIZE, DURATION

A prospective pregnancy study with preconception enrollment was conducted between 2005 and 2009. Among the 344 women who became pregnant during the Longitudinal Investigation of Fertility and the Environment (LIFE) study, 337 (98%) had salivary biomarker data for analysis.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Couples planning pregnancy were followed for up to 12 months as they tried to become pregnant and through pregnancy if it occurred. Participating women collected a basal saliva sample on the morning following enrollment and a second on the morning following their next menses to measure cortisol and alpha-amylase, biomarkers of stress. Women used home pregnancy tests on the day of expected menses. A pregnancy loss was defined as a negative pregnancy test following a positive pregnancy test, the onset of menses, or for pregnancies that survived to clinical recognition, recognition of the loss by a healthcare provider.

MAIN RESULTS AND THE ROLE OF CHANCE

Among the 337 couples, the median age of female and male partners was 29 and 31 years, respectively. Most of the women were non-Hispanic white (83%) and highly educated. There were 97 pregnancy losses reported among the 337 pregnancies. The median gestational age at loss was 6 weeks 5 days with only two losses occurring in the second trimester. Using Cox proportional hazards models, we found no clear pattern of association between two preconceptional biomarkers of stress (salivary cortisol and alpha-amylase concentrations) modeled both continuously or in tertiles and incident pregnancy loss after adjustment for confounders.

LIMITATIONS REASONS FOR CAUTION

Our prior work suggests that women enrolled in the LIFE Study had lower stress levels than women in the general population. Owing to concerns regarding participant burden, we were unable to collect serial saliva measurements, which would have allowed us to examine the association between stress in early pregnancy and pregnancy loss. Further, with regard to the measurement of perceived stress, the Cohen's Perceived Stress Scale was only administered at baseline. While every attempt was made to ensure diversity in the cohort, non-Hispanic white women were over-represented, therefore it is possible that the results might not be generalizable to all women.

WIDER IMPLICATIONS OF THE FINDINGS

In one of the largest studies in the USA to prospectively capture data on the incidence of early pregnancy loss, we found no clear association between two biomarkers of preconception stress (measured in saliva) and pregnancy loss.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported by the Intramural Research Program of the Eunice Kennedy Shriver National Institute of Child Health and Human Development (contracts #N01-HD-3-3355, N01-HD-3-3356, N01-HD-3358). There are no conflicts of interest to declare.

TRIAL REGISTRATION NUMBER

Not applicable.

The role of indoleamine-2,3-dioxygenase in normal and pathological pregnancies

The survival of allogeneic fetus during pregnancy contradicts the laws of immune responses. Behind this paradoxical phenomenon, the mechanism is quite complex. Indoleamine-2,3-dioxygenase (IDO) is the first and rate-limiting enzyme of tryptophan catabolism. Emerging evidence shows that IDO is expressed at the maternal-fetal interface, including trophoblast cells, decidual stroma cells, decidual immune cells (eg, natural killer cells, T cells, and macrophages), and vascular endothelial cells of decidua and chorion. Moreover, the expression and activity of IDO are different among non-pregnant, normal pregnant, and pathological pregnant conditions. IDO plays important roles in normal pregnancy through immune suppression and regulation of fetal invasion and circulation. However, the abnormal expression and dysfunction of IDO are associated with some pathological pregnancies (including recurrent spontaneous abortion, preeclampsia, preterm labor, and fetal growth restriction).

Redox Properties of Tryptophan Metabolism and the Concept of Tryptophan Use in Pregnancy

During pregnancy, tryptophan (Trp) is required for several purposes, and Trp metabolism varies over time in the mother and fetus. Increased oxidative stress (OS) with high metabolic, energy and oxygen demands during normal pregnancy or in pregnancy-associated disorders has been reported. Taking the antioxidant properties of Trp and its metabolites into consideration, we made four hypotheses. First, the use of Trp and its metabolites is optional based on their antioxidant properties during pregnancy. Second, dynamic Trp metabolism is an accommodation mechanism in response to OS. Third, regulation of Trp metabolism could be used to control/attenuate OS according to variations in Trp metabolism during pregnancy. Fourth, OS-mediated injury could be alleviated by regulation of Trp metabolism in pregnancy-associated disorders. Future studies in normal/abnormal pregnancies and in associated disorders should include measurements of free Trp, total Trp, Trp metabolites, and activities of Trp-degrading enzymes in plasma. Abnormal pregnancies and some associated disorders may be associated with disordered Trp metabolism related to OS. Mounting evidence suggests that the investigation of the use of Trp and its metabolites in pregnancy will be meanful.

Dendritic cells transfected with indoleamine 2,3-dioxygenase gene suppressed acute rejection of cardiac allograft

BACKGROUND

Immunomodulation by indoleamine 2,3-dioxygenase (IDO) has been documented in many studies yet its underlying mechanisms remain undefined, especially in solid organ transplantation. Recent research demonstrated that the active expression of IDO in dendritic cells (DCs) regulates immune reaction. This study assessed whether DCs transfected with IDO gene inhibit T cells responses and suppress cardiac allograft rejection.

METHODS

Adenovirus vector containing IDO gene was transfected into DCs to obtain IDO-positive DCs (IDO(+) DCs). To evaluate the effect of IDO(+) DCs on T cells in vitro, CD4(+) T cell proliferation and apoptosis was assessed in mixed lymphocyte reactions and measured by flow cytometry, respectively. IDO(+) DCs from C57BL/6 mice were injected into BALB/c recipients before heterotopic cardiac transplantation.

RESULTS

Supernatant fluids from cultures of IDO(+) DCs had decreased tryptophan and increased kynurenine levels, reflecting IDO activity. IDO(+) DCs suppressed CD4(+) T cell responses in vitro, as reflected by decreased proliferation and increased apoptosis. In the transplant model, IDO(+) DCs prolonged survival and alleviated rejection of cardiac allograft in recipients injected with IDO(+) DCs. In vivo, IDO(+) DCs also significantly impaired CD4(+) T cell responses promoting increased apoptosis and a Th2-dominant cytokine shift.

CONCLUSIONS

IDO overexpression in DCs suppressed T cells alloresponses in vitro, and IDO(+) DCs attenuated acute allograft rejection in vivo. Regulation of tryptophan catabolism by means of IDO overexpression in DCs may be a useful approach in cardiac transplantation and immunological tolerance.

Dysregulated expression of IDO may cause unexplained recurrent spontaneous abortion through suppression of trophoblast cell proliferation and migration

In pregnancy, trophoblast proliferation, migration and invasion are important for the establishment and maintenance of a successful pregnancy. Impaired trophoblast function has been implicated in recurrent spontaneous abortion (RSA), a major complication of pregnancy, but the underlying mechanisms remain unclear. Indoleamine 2,3-dioxygenase (IDO), an enzyme that catabolizes tryptophan along the kynurenine pathway, is highly expressed in the placenta and serum during pregnancy. Here, we identified a novel function of IDO in regulating trophoblast cell proliferation and migration. We showed that IDO expression and activity were decreased in unexplained recurrent spontaneous abortion (URSA) compared to normal pregnancy. Furthermore, blocking IDO in human trophoblast cells led to reduced proliferation and migration, along with decreased STAT3 phosphorylation and MMP9 expression. Increased STAT3 phosphorylation reversed the IDO knockdown-suppressed trophoblast cell proliferation and migration. In addition, the overexpression of IDO promoted cell proliferation and migration, which could be abolished by the STAT3 signaling inhibitor (AG490). Finally, we observed similar reductions of STAT3 phosphorylation and MMP9 expression in URSA patients. These results indicate that the level of IDO expression may be associated with pregnancy-related complications, such as URSA, by affecting trophoblast cell proliferation and migration via the STAT3 signaling pathway.

Interferons

Interferon was discovered by Alick Isaacs and Jean Lindenmann in 1957. It was originally thought that interferon could be used as a general anti-viral agent and in anti-cancer therapy. There are many different types of interferons, now known as interferons “alpha,” “beta,” “gamma” and “lambda,” with different cellular receptors and modes of action, and there are possibly 24 different types of alpha interferon. Independently and simultaneously, a group of Japanese scientists found an “interfering factor,” which upon subsequent analysis turned out to be interferon, probably of the alpha type. The interferon alpha gene was the first mammalian gene to be cloned in a bacterial system and became the prototype for gene cloning technology. Until the cloning of the interferons in Escherichia coli, and expression of the interferon genes in mammalian cells in culture, it was impossible to obtain enough material for clinical use. Interferon today is predominantly used in the treatment of hepatitis B and C, leukemia and Kaposi’s sarcoma. As an anti-viral agent, interferon has not lived up to its initial promise, since in vitro most viruses block the activity of interferon and clinical trials have given inconclusive results with severe side effects. Interferon induces hundreds of genes in vivo and in vitro, each interferon producing overlapping and distinct gene profiles. The mechanism of both interferon induction and anti-viral response is complicated and involves the interaction of many regulatory molecules. Interferon is now known to be a component of the large family of cytokines or interleukins.

Unexplained infertility patients have increased serum IL-2, IL-4, IL-6, IL-8, IL-21, TNFα, IFNγ and increased Tfh/CD4 T cell ratio: increased Tfh and IL-21 strongly correlate with presence of autoantibodies

Infertility is a disease of the reproductive system that affects millions of people globally. Reproductive failure is a major medical issue adversely affecting human health in the 21st century. Many factors contribute to infertility, including immune conditions which may lead to immune infertility (immunologic infertility). It is known that specific T helper cells (Th) and their cytokines are involved in the stages of infertility. The aim of this study is to provide a new diagnostic approach to immunologic infertility by investigating the correlation of follicular helper T cells (Tfh) and their secreted cytokines with the autoantibodies in peripheral blood samples from immunologically infertile patients. Thirty (30) patients suffering from immune infertility and 20 control subjects were selected as the sample base for this study. The levels of Tfh, 20 cytokines and 4 antibodies were evaluated for this investigation and evaluated using flow cytometry, antibody chip and ELISA technologies. It was found that, in immunologically infertile patients, Tfh cell numbers were significantly higher than those in the control group. Likewise, seven (7) serum cytokines were expressed to a greater degree in infertile patients compared to the control group. Finally, four (4) antibodies were found to be higher in immunologically infertile patients. The results show that, among patients with immunologic infertility, the levels of Tfh cells and IL-21 were increased significantly in peripheral blood samples and correlate positively with the autoantibodies. IL-12 was positively correlated with the two antibodies, while TNFα was negatively correlated with two additional antibodies. The detection and quantification of Tfh cells, IL-21, IL-12 and TNFα may provide new diagnostic indicators to screen for immunologic infertility.

Immunological modes of pregnancy loss: inflammation, immune effectors, and stress

Inflammatory immune response plays a key role in reproductive failures such as multiple implantation failures (MIF), early pregnancy loss, and recurrent pregnancy losses (RPL). Cellular immune responses particularly mediated by natural killer (NK), and T cells are often dysregulated in these conditions. Excessive or inappropriate recruitment of peripheral blood NK cells to the uterus may lead to cytotoxic environment in utero, in which proliferation and differentiation of trophoblast is hampered. In addition, inadequate angiogenesis by uterine NK cells often leads to abnormal vascular development and blood flow patterns, which, in turn, leads to increased oxidative stress or ischemic changes in the invading trophoblast. T-cell abnormalities with increased Th1 and Th17 immunity, and decreased Th2 and T regulatory immune responses may play important roles in RPL and MIF. A possible role of stress in inflammatory immune response is also reviewed.

N-(3', 4'-dimethoxycinnamonyl) anthranilic acid alleviated experimental colitis by inhibiting autoimmune response and inducing CD4+ CD25+ regulatory T cells production

BACKGROUND AND AIM

Crohn's disease treatments available today are not quite satisfactory. N-(3', 4'-dimethoxycinnamonyl) anthranilic acid (3, 4-DAA) has been proved to be effective in many autoimmune diseases. Therefore, we investigated the immunologic function of 3, 4-DAA on trinitrobenzene sulfonic acid (TNBS) colitis and human Crohn's disease.

METHODS

Mice with TNBS-induced colitis were treated with 3, 4-DAA or 1-methyl-tryptophan (1-MT). Colitis severity was assessed with clinical and histological scores. Cell proliferation, cytokine expression, and the percentage of CD4(+) CD25(+) T cells were measured in both mice and human samples.

RESULTS

In mice treated with 3, 4-DAA, the clinical and histological scores were decreased (P < 0.05); the proliferation of mesenteric lymph nodes (MLNs) cells and lamina propria mononuclear cells (LPMCs) were inhibited (P < 0.05); Th1 cytokine expressions were decreased (P < 0.05), and Th2 cytokine levels were increased (P < 0.05). 3, 4-DAA also induced CD4(+) CD25(+) T cells expression (5.88 ± 2.1 vs 11.03 ± 2.93, P < 0.05) in mice MLNs. Transfer of these cells into TNBS colitis mice resulted in the reduction of the disease activity index (DAI) and histological scores. In LPMCs isolated from human Crohn's disease, 3, 4-DAA had the same effect. It can inhibit the cell proliferation, decrease Th1 cytokine expressions (P < 0.05), and increase Th2 cytokine levels (P < 0.05). The percentage of CD4(+) CD25(+) T cells were also increased (1.60 ± 0.14 vs 2.45 ± 0.50, P < 0.05). 1-MT treatment led to opposite outcomes.

CONCLUSION

3, 4-DAA can alleviate the severity of colitis through inhibiting Th1 cells response, promoting Th2 cytokines expression and inducing CD4(+) CD25(+) T cells expression.

Immunotherapy of patients with recurrent spontaneous miscarriage and idiopathic infertility: does the immunization-dependent Th2 cytokine overbalance really matter?

Recurrent spontaneous miscarriage (RSM) and idiopathic infertility (IIF) are partially caused by immunologic disturbances. Paternal lymphocyte immunization (PLI) is proposed for restoration of the proper Th1/Th2 balance in these patients, but still there are controversies on PLI mechanism, its efficacy and identification of patients who may benefit from this therapy. The study group consisted of n = 34 RSM and n = 42 IIF women with unexplained miscarriage or IIF. PLI was offered as a treatment in both groups. Peripheral blood lymphocyte (PBL) populations (CD3(+), CD3(-)/CD19(+), CD3(+)/CD4(+), CD3(+)/CD8(+), CD3(-)/CD16(+)CD56(+)) were studied before immunization, while PBL cytokine secretion (IFN-γ, TNF-α, IL-10, IL-5, IL-4, IL-2), before and after immunization, pre-conceptionally in both groups. The reference PBL ratio and cytokine levels were adopted from previously studied normal fertile women. PBL populations, concentration and ratio of Th1/Th2 cytokines did not differ between RSM and IIF patients. Compared to the results observed in normal fertile women the levels of IFN-γ, TNF-α and IL-2 were higher, while IL-10 lower in both RSM and IIF patients (p < 0.01). After immunization a decrease of IFN-γ (RSM and IIF groups) and IL-4 and IL-10 (RSM group) were observed, as well as an increase in TNF-α/IL-4 ratio (RSM group) (p < 0.05). No differences in Th1/Th2 concentration and ratio between patients with successful and unsuccessful pregnancy were observed. No significant correlations between success and particular cytokine concentration were observed. Concentrations of Th1/Th2 cytokines and PBL populations did not differ between RSM and IIF women. Th1 shift in both RSM and IIF patients was observed in comparison to fertile women. Treatment with PLI-induced pre-conceptionally cytokine changes which neither indicated Th2 shift nor correlated with subsequent pregnancy success.

The immunoprotective role of interleukin-10 in abnormal pregnancy outcome induced by Toxoplasma gondii infection

AIMS

To investigate the immunoprotective effect of IL-10 on pregnancy in Toxoplasma gondii-infected C57BL/6 mice.

METHODS

Twenty-four pregnant mice were randomly divided into 3 equal groups, i.e. a control group (CG), an infected group (IG) and an infected group treated with IL-10 (IPTG). Each IPTG and IG mouse was infected with 400 T. gondii trophozoites on gestational day (GD) 8. Each IPTG mouse was injected with 1 μg recombinant mouse IL-10 via a tail vein on GD 10 and 12. The mice were sacrificed on day 7 postinfection. Qa-1 and NKG2A were analyzed in the placenta by flow cytometry and real-time PCR. IL-4, IL-10 and IFN-γ in the placenta supernatant were analyzed by ELISA. Statistical analysis was performed by one-way ANOVA.

RESULTS

IPTG mice showed a better mental state, had larger fetuses and placentas with a better blood supply and a lower resorption ratio compared to IG mice. NKG2A and Qa-1 were significantly increased in IPTG mice compared to IG mice (p < 0.05). IL-4 and IL-10 in IPTG placenta supernatant were increased (p < 0.05), but IFN-γ was decreased (p < 0.05) compared to IG placenta supernatant. The ratios of IFN-γ/IL-4 and IFN-γ/IL-10 were decreased in IPTG mice compared to IG mice (p < 0.05, p < 0.05).

CONCLUSION

IL-10 plays an immunoprotective role and improves the pregnancy outcome of T. gondii-infected mice.

Mother-offspring dialogue in early pregnancy: impact of adverse environment on pregnancy maintenance and neurobiology

The mother-offspring dialogue begins even before implantation and is essential to signal pregnancy, establish robust contact, and maintain embryo growth and development. Any circumstance that disrupts the dialogue risks pregnancy problems. A new look at how stress impacts on pregnancy involves its adverse effects on the key pregnancy hormones of progesterone and prolactin. These effects have far-reaching consequences on pregnancy maintenance, maternal anxiety and embryo programming. This review focuses on early pregnancy and how stress might compromise the multi-layer, two-way communication between mother and embryo.

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.

Single-molecule-counting protein microarray assay with nanoliter samples and its application in the dynamic protein expression of living cells

A novel ultra-sensitive single-molecule-counting microarray assay (SMCMA) with a 1.8-nL sample volume for quantification of proteins was provided using total internal reflection fluorescence microscopy coupled with quantum dot (QD)-labeling. In the SMCMA, the microarray consisting of ∼ 300 μm diameter microspots with the spot-to-spot pitch distance of 500 μm was fabricated by spotting 1.8 nL of solutions containing the target protein onto the substrate which was modified with primary antibody of the protein and blocked with ethanolamine and BSA using a pin-tool type microarraying robot. Then, biotinylated secondary antibody of the protein was bound to the protein to form sandwich immunocomplexes. After labeling with streptavidin-coated QDs, the whole image of the microarray was acquired using a homemade single-molecule microarray reader. The target protein was quantified based on the number of bright dots from the QDs corresponding to single target protein molecules on the microarray. Using the SMCMA, an amount as low as 1.5 × 10(-21) mole (904 molecules) for proteins could be detected. The SMCMA was applied to measure dynamic expression of osteopontin in living cells.

Baby on board: do responses to stress in the maternal brain mediate adverse pregnancy outcome?

Stress and adverse environmental surroundings result in suboptimal conditions in a pregnant mother such that she may experience poor pregnancy outcome including complete pregnancy failure and preterm labor. Furthermore her developing baby is at risk of adverse programming, which confers susceptibility to long term ill health. While some mechanisms at the feto-maternal interface underlying these conditions are understood, the underlying cause for their adverse adaptation is often not clear. Progesterone plays a key role at many levels, including control of neuroendocrine responses to stress, procuring the required immune balance and controlling placental and decidual function, and lack of progesterone can explain many of the unwanted consequences of stress. How stress that is perceived by the mother inhibits progesterone secretion and action is beginning to be investigated. This overview of maternal neuroendocrine responses to stress throughout pregnancy analyses how they interact to compromise progesterone secretion and precipitate undesirable effects in mother and offspring.

Fetal rejection: infertility and immunity

Defective reaction toward fetal alloantigens could result in both recurrent spontaneous abortions (RSAs) and recurrent early pregnancy failures (REPFs), the latter existing in couples with unexplained infertility and multiple failures of implantation after in vitro fertilization embryo transfer. Immunological mechanisms leading to RSA and REPF seem to be different, although both syndromes probably have a genetic background that has not been identified so far. Despite the fact that antiphospholipid syndrome is a well-established cause of repeated pregnancy loss, the role of different autoantibodies existing in RSA and REPF patients needs to be elucidated. Immunotherapy is believed to correct the detrimental immune reactions; however, its real effectiveness and safety for the treatment of distinct forms of pregnancy loss need to be reconsidered.

Immune cells and molecules in pregnancy: friends or foes to the fetus?

Considering allograft rejection as a basic feature of the immune system, the mammalian pregnancy is an immunological paradox where the semi-allogeneic fetus is not rejected. How are the demands of pregnancy solved in the context of maternal immunity? Medawar's original proposal of maternal immune inertness during pregnancy should be revised to active materno-placental tolerance. Multiple mechanisms are involved in peripheral and local tolerance induction that prevents fetal rejection while maintaining competent immune surveillance and protection. The goal of this review is to discuss the major cellular and molecular components of the immune system that control and promote fetal survival.

Urine neopterin concentrations as a marker for successful blastocyst implantation after assisted reproductive technologies

Successful blastocyst implantation requires intricately orchestrated adaptation processes involving maternal and fetal mediators. The pivotal role of distinct immune response pathways in early pregnancy is widely acknowledged. Pro-inflammatory cytokines, e.g. interferon-gamma (IFN-gamma), are the primary inducers of tryptophan-degrading enzyme indoleamine 2,3-dioxygenase (IDO) and of neopterin biosynthesis by GTP-cyclohydrolase I. IDO activity has been proposed to be of high clinical relevance in the context of pregnancy. To date, insights arising from clinical studies on IDO activity and neopterin concentration during the very early days of pregnancy are still few. Early morning urinary neopterin concentrations in 61 women undergoing assisted reproduction treatment (72 cycles in total) were examined, upon exclusion of infections, daily over a period of 2 weeks after embryo transfer. Twenty of the study participants (28%) became successfully pregnant, and four women experienced abortion. Neopterin concentrations significantly increased after blastocyst transfer when implantation was successful (chi-squared=23.291, P<0.01; Friedman test), opposed to non-significant changes of neopterin in women with unsuccessful treatment (chi-squared=8.203). The steady increase of neopterin concentrations upon blastocyst transfer indicates that heightened production of neopterin in very early phases of pregnancy may serve as an early predictor of successfully progressing pregnancies in humans.

Progesterone-induced blocking factor (PIBF) modulates cytokine production by lymphocytes from women with recurrent miscarriage or preterm delivery

Spontaneous miscarriage and preterm delivery are common complications of pregnancy. Pro-inflammatory cytokines have been shown to be associated with recurrent spontaneous miscarriage (RSM) and preterm delivery (PTD) and these have led to exploration of ways to downregulate pro-inflammatory cytokines and/or to upregulate anti-inflammatory cytokines. Progesterone-induced blocking factor (PIBF) is a molecule with inhibitory effects on cell-mediated immune reactions. We have ascertained the effects of PIBF on secretion of selected type 1 and type 2 cytokines by peripheral blood mononuclear cells from healthy non-pregnant women, women undergoing normal pregnancy, women with unexplained RSM and women with PTD. Peripheral blood mononuclear cells from 30 women with a history of unexplained RSM, 18 women undergoing PTD, 11 women with normal pregnancy and 13 non-pregnant healthy women were stimulated with a mitogen in the absence and presence of PIBF after which the levels of cytokines released into culture supernatants were determined by ELISA. Production of the type 2 cytokines IL-4, IL-6 and IL-10 by lymphocytes from the RSM and PTD groups and of IL-4 and IL-10 by lymphocytes from healthy pregnant women was significantly increased upon exposure to PIBF, while the levels of type 1 cytokines were not affected. Ratios of type 1:type 2 cytokines were decreased, suggesting a shift towards Th2 bias. PIBF did not affect cytokine production by lymphocytes from non-pregnant women. Thus, PIBF acts on lymphocytes in pregnancy to induce a type 1 to type 2 cytokine shift by upregulating the production of type 2 cytokines.

T-bet, pSTAT1 and pSTAT3 expression in peripheral blood mononuclear cells during pregnancy correlates with post-partum activation of multiple sclerosis

In pregnant women affected by multiple sclerosis (MS) we observed increased percentages of CD4(+)CD25(+)Foxp3(+) T regulatory cells at the 1st and the 2nd trimester of gestation that was associated with a decreased T-bet expression in CD4(+) T cells. In women showing clinical relapse and/or new lesions at MRI after delivery we found, a higher expression of T-bet, pSTAT1 and pSTAT3 in CD4(+), CD8(+) T cells and CD14(+) cells, associated with an increase of IFNgamma and IL17 production by PBMC at the 3rd trimester of gestation and after delivery. Our data suggest that the expansion of circulating CD4(+)CD25(+)Foxp3(+) regulatory T cells and the lower expression of T-bet in CD4(+) T cells may account for the decreased MS activity during pregnancy. The expression of T-bet, pSTAT1 and pSTAT3 in peripheral blood CD4(+) and CD8(+) T cells and monocytes could be useful to identify MS patients who will develop a relapse after delivery.

IDO: a double-edged sword for T(H)1/T(H)2 regulation

Indoleamine 2,3-dioxygenase (IDO) has been well defined as one of the important immunosuppressive properties for T(H)1 cell-mediated immune responses, but its function in T(H)2 dominant system is poorly understood. Recently, an appreciable number of publications suggest that the role of IDO in T(H)2 cell regulation may be different from that of T(H)1 immune responses. Here we review the evidence on the regulatory function of IDO and tryptophan metabolites in T(H)1/T(H)2 differentiation. We propose that IDO-kynurenine pathway can serve as a negative feedback loop for T(H)1 cells but it may play a distinct role in up-regulating T(H)2 dominant immune responses.

Tolerance signaling molecules and pregnancy: IDO, galectins, and the renaissance of regulatory T cells

PROBLEM

Is the concept of maternal tolerance preventing rejection of the semi-allogeneic 'fetal allograft' still valid?

METHOD OF STUDY

Compilation of expert reviews of literature and recent advances in research on indoleamine-2,3 dioxygenase (IDO), regulatory T cells and galectin-1.

RESULTS AND CONCLUSION

A role for IDO in pregnancy success remains speculative, but solid data exist to support a role for Treg cells, and for galectin-1 in induction and action of Treg cells. Just as several signals may need to be simultaneously present to induce Th1 cytokine-triggered abortions, more than 1 signal may need to be simultaneously present to prevent rejection and ensure success. Both complement and coagulation pathways appear necessary for embryo execution.

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.

The Th1/Th2 paradigm: still important in pregnancy?

The enunciation of the T helper 1/T helper 2 (Th1/Th2) paradigm in pregnancy has represented a major step forward in our understanding of physiological and pathologic materno-foetal relationship. However, recent developments in studies of the implantation process and in the emergence of the uterine vascular bed and its control by natural killer cells and cytokines suggest that one must go beyond this hitherto useful scheme. In this review, we replace the emergence of the paradigm in its historical context and then emphasises what it does explain and what it no longer account for. A final reappraisal of the paradigm is suggested.

Why much of the pathophysiology of preeclampsia-eclampsia must be of an autoimmune nature

Preeclampsia-eclampsia (PE-E) is a poorly understood condition of human pregnancy, which can affect multiple organs and is a leading cause of maternal deaths worldwide. The etiology and pathophysiology remain enigmas, however, which hampers progress in prevention, diagnosis, and treatment of this condition. PE-E is characterized by many features typically seen in autoimmune diseases, or in association with autoimmune reactions. Although this does not mean that PE-E should be considered an autoimmune condition, it does suggest that abnormal autoimmune processes play an important part in the clinical presentation of PE-E. In that regard, PE-E mimics autoimmune responses also observed in situations of allograft rejection and graft-versus-host disease (GVHD). Indeed, PE-E shares many other clinical and laboratory characteristics with allograft rejection and GVHD. Recognizing PE-E as a clinical condition that is characterized by autoimmune abnormalities may facilitate earlier and more specific diagnosis, along with preventive and more specific therapies for women at risk.

Immunological analogy between allograft rejection, recurrent abortion and pre-eclampsia - the same basic mechanism?

There are still controversies concerning the role of immunological mechanisms engaged both in recurrent abortions (RA) and pre-eclampsia (PE). According to some opinions, recurrent miscarriage is comparable to organ-specific autoimmune disease. Analysis of immune reactions shows that graft rejection shares many similar mechanisms with RA and PE. This fact allows us to conclude that rejection of transplanted alloantigenic organs and pregnancy loss have probably the same evolutionary origin. Subsets and functions of immunocompetent cells (T CD4, suppressor gammadeltaT, cytotoxic T CD8, Treg, Tr1, uterine NK cells), over-activation of innate immunity (activation of NK cytotoxic cells, macrophages, neutrophils and complement), changes of Th1/Th2 cytokine balance (IL-2, IL-12, IL-15, IL-18, IFNgamma, TNFalpha vs. IL-4, IL-10, TGFbeta), importance of HLA-G molecule, CD200/CD200R interaction, over-expression of adhesion molecules, fgl2 prothrombinase activation and stimulation of IDO and HO expression, all suggest that RA and PE are syndromes of fetal allograft rejection, and not organ-specific autoimmune diseases. According to that supposition, an analogy might exist between acute graft rejection and recurrent abortion, and between chronic graft rejection and pre-eclampsia.

Disturbances in placental immunology: ready for therapeutic interventions?

Recent studies have provided new insight into aberrations in the immunological interplay between mother and fetus and their potential role in the development of recurrent fetal loss and preeclampsia. The action of anti-phospholipid antibodies in recurrent fetal loss is now proposed to involve the complement system, neutrophil activation and the production of TNFalpha by immune bystander cells. A clear involvement of the immune system is emerging in preeclampsia, involving mainly the innate arm, especially neutrophils. The activation of peripheral neutrophils by placentally released inflammatory debris triggers the induction of neutrophil extracellular traps (NETs), which may lead to an occlusion of the intervillous space, thereby further promoting a condition of placental hypoxia. It has, hence, been suggested that new therapeutic strategies be developed, including the possible use of TNFalpha antagonists in cases of recurrent miscarriage. These strategies need to be addressed with caution due to the possible induction of fetal congenital abnormalities.

Cortisol levels and very early pregnancy loss in humans

Maternal stress is commonly cited as an important risk factor for spontaneous abortion. For humans, however, there is little physiological evidence linking miscarriage to stress. This lack of evidence may be attributable to a paucity of research on maternal stress during the earliest gestational stages. Most human studies have focused on "clinical" pregnancy (>6 weeks after the last menstrual period). The majority of miscarriages, however, occur earlier, within the first 3 weeks after conception (approximately 5 weeks after the last menstrual period). Studies focused on clinical pregnancy thus miss the most critical period for pregnancy continuance. We examined the association between miscarriage and levels of maternal urinary cortisol during the first 3 weeks after conception. Pregnancies characterized by increased maternal cortisol during this period (within participant analyses) were more likely to result in spontaneous abortion (P < 0.05). This evidence links increased levels in this stress marker with a higher risk of early pregnancy loss in humans.

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.

T cells in normal pregnancy and recurrent pregnancy loss

This review focuses on the possible role of T cells in successful pregnancy and in unexplained recurrent abortion. The functions exhibited by Th1 and Th2 cells have suggested, perhaps in a simplistic way, that Th1-type cytokines, which promote allograft rejection, may compromise pregnancy, whereas the Th2-type cytokines, by inhibiting Th1 responses, promote allograft tolerance and therefore may improve fetal survival. However, Th1 cytokines are not always detrimental for pregnancy development. Th1 cytokines, depending on their time of expression, stage of gestation and relative concentrations, could have a positive role in successful pregnancy. Other cytokines (LIF, M-CSF) produced by T cells seem to be important for the maintenance of pregnancy. Hormones present in the microenvironment of the decidual T cells could be responsible, at least in part, for the cytokine profile of the T cells. Indeed, progesterone is a potent inducer of Th2-type cytokines (e.g. IL-4 and IL-5), LIF and M-CSF production by T cells, whereas relaxin induces T cells to produce IFNgamma. Of course, the success of pregnancy depends on many mechanisms induced by different type of cells. Th2 cells could be one of these.