Immunopathology of the implantation site utilizing monoclonal antibodies to natural killer cells in women with recurrent pregnancy losses

The Update Immune-Regulatory Role of Pro- and Anti-Inflammatory Cytokines in Recurrent Pregnancy Losses

Recurrent pregnancy losses (RPL) is a common reproductive disorder with various underlying etiologies. In recent years, rapid progress has been made in exploring the immunological mechanisms for RPL. A propensity toward Th2 over Th1 and regulatory T (Treg) over Th17 immune responses may be advantageous for reproductive success. In women with RPL and animals prone to abortion, an inordinate expression of cytokines associated with implantation and early embryo development is present in the endometrium or decidua secreted from immune and non-immune cells. Hence, an adverse cytokine milieu at the maternal-fetal interface assaults immunological tolerance, leading to fetal rejection. Similar to T cells, NK cells can be categorized based on the characteristics of cytokines they secrete. Decidual NK (dNK) cells of RPL patients exhibited an increased NK1/NK2 ratio (IFN-γ/IL-4 producing NK cell ratios), leading to pro-inflammatory cytokine milieu and increased NK cell cytotoxicity. Genetic polymorphism may be the underlying etiologies for Th1 and Th17 propensity since it alters cytokine production. In addition, various hormones participate in cytokine regulations, including progesterone and estrogen, controlling cytokine balance in favor of the Th2 type. Consequently, the intricate regulation of cytokines and hormones may prevent the RPL of immune etiologies. Local or systemic administration of cytokines or their antagonists might help maintain adequate cytokine milieu, favoring Th2 over Th1 response or Treg over Th17 immune response in women with RPL. Herein, we provided an updated comprehensive review regarding the immune-regulatory role of pro- and anti-inflammatory cytokines in RPL. Understanding the roles of cytokines involved in RPL might significantly advance the early diagnosis, monitoring, and treatment of RPL.

Number and function of uterine natural killer cells in recurrent miscarriage and implantation failure: a systematic review and meta-analysis

BACKGROUND

Uterine natural killer cells (uNK) are the most abundant lymphocytes found in the decidua during implantation and in first trimester pregnancy. They are important for early placental development, especially trophoblast invasion and transformation of the spiral arteries. However, inappropriate uNK function has been implicated in reproductive failure, such as recurrent miscarriage (RM) or recurrent implantation failure (RIF). Previous studies have mainly focussed on peripheral NK cells (pNK), despite the well-documented differences in pNK and uNK phenotype and function. In recent years, there has been an explosion of studies conducted on uNK, providing a more suitable representation of the immune environment at the maternal-foetal interface. Here, we summarize the evidence from studies published on uNK in women with RM/RIF compared with controls.

OBJECTIVE AND RATIONALE

The objectives of this systematic review and meta-analysis are to evaluate: differences in uNK level in women with RM/RIF compared with controls; pregnancy outcome in women with RM/RIF stratified by high and normal uNK levels; correlation between uNK and pNK in women with RM/RIF; and differences in uNK activity in women with RM/RIF compared with controls.

SEARCH METHODS

MEDLINE, EMBASE, Web of Science and Cochrane Trials Registry were searched from inception up to December 2020 and studies were selected in accordance with PRISMA guidelines. Meta-analyses were performed for uNK level, pregnancy outcome and uNK/pNK correlation. Narrative synthesis was conducted for uNK activity. Risk of bias was assessed by ROBINS-I and publication bias by Egger's test.

OUTCOMES

Our initial search yielded 4636 articles, of which 60 articles were included in our systematic review. Meta-analysis of CD56+ uNK level in women with RM compared with controls showed significantly higher levels in women with RM in subgroup analysis of endometrial samples (standardized mean difference (SMD) 0.49, CI 0.08, 0.90; P = 0.02; I2 88%; 1100 women). Meta-analysis of CD56+ uNK level in endometrium of women with RIF compared with controls showed significantly higher levels in women with RIF (SMD 0.49, CI 0.01, 0.98; P = 0.046; I2 84%; 604 women). There was no difference in pregnancy outcome in women with RM/RIF stratified by uNK level, and no significant correlation between pNK and uNK levels in women with RM/RIF. There was wide variation in studies conducted on uNK activity, which can be broadly divided into regulation and receptors, uNK cytotoxicity, cytokine secretion and effect of uNK on angiogenesis. These studies were largely equivocal in their results on cytokine secretion, but most studies found lower expression of inhibitory receptors and increased expression of angiogenic factors in women with RM.

WIDER IMPLICATIONS

The observation of significantly increased uNK level in endometrium of women with RM and RIF may point to an underlying disturbance of the immune milieu culminating in implantation and/or placentation failure. Further research is warranted to elucidate the underlying pathophysiology. The evidence for measuring pNK as an indicator of uNK behaviour is sparse, and of limited clinical use. Measurement of uNK level/activity may be more useful as a diagnostic tool, however, a standardized reference range must be established before this can be of clinical use.

Understanding human immunity in idiopathic recurrent pregnancy loss

Miscarriage, defined as the loss of a pregnancy before a viable gestation, affects 1 in 6 couples. Recurrent pregnancy loss (RPL), defined as two or more miscarriages, affects up to 1.9% of couples. The physical, psychological, and financial impact of miscarriage can be substantial. However, despite its multifactorial etiology, for up to 50% of couples a reason behind this condition cannot be identified, termed 'idiopathic RPL'. Much recent research has strived to understand this, with immune dysregulation being a source of particular interest. In this short review we summarize the current evidence on the complex role of the immune system both pre- and early post-conception in RPL. A key question is whether systemic peripheral blood markers, in particular natural killer cell and T cells, may be utilized to accurately predict and/ or diagnose those pregnancies at high risk of loss. Given the invasive nature of endometrial testing, identification of reliable peripheral immune biomarkers is particularly appealing. Clinical trials using potent immunomodulatory agents, including intravenous immunoglobulin, donor leukocyte immunization, and tumor necrosis factor (TNF)-α inhibitors, have been undertaken with the primary objective of preventing miscarriage in women with RPL. Standardisation of both diagnostic and prognostic immune cell testing assays is required to permit accurate identification of those women who may benefit from immunomodulation. Prompt clarification is required to meet the increasing expectation from couples and clinicians, as without these advancements women are at risk of exposure to potent immune-therapies and subsequent studies are at risk of failure, generating further controversy regarding the role of immune dysregulation in women with RPL. Through this review we highlight clear gaps in our current knowledge on immune activity in RPL.

Transcriptome study of receptive endometrium in overweight and obese women shows important expression differences in immune response and inflammatory pathways in women who do not conceive

Obesity and being overweight are growing worldwide health problems that also affect women of reproductive age. They impair women’s fertility and are associated with lower IVF success rates. The mechanism by which increased body weight disrupts fertility has not yet been established. One possibility is that it affects the process of embryo implantation on the endometrial level. The purpose of our study was to determine the differences in enriched biological pathways in the endometrium of overweight and obese women undergoing IVF procedures. For this purpose, 14 patients (5 pregnant, 9 non-pregnant) were included in the study. Endometrial samples were obtained during the window of implantation and RNA sequencing was performed. There were no differences in general patient’s and IVF cycle characteristics between pregnant and non-pregnant women. In the endometrial samples of women who did not conceive, pathways related to the immune response, inflammation, and reactive oxygen species production were over-expressed. Our findings show that the reason for implantation failure in overweight and obese women could lie in the excessive immune and inflammatory response at the endometrial level.

Uterine natural killer cell biology and role in early pregnancy establishment and outcomes

Objective

While immune cells were originally thought to only play a role in maternal tolerance of the semiallogenic fetus, an active role in pregnancy establishment is becoming increasingly apparent. Uterine natural killer (uNK) cells are of specific interest because of their cyclic increase in number during the window of implantation. As a distinct entity from their peripheral blood counterparts, understanding the biology and function of uNK cells will provide the framework for understanding their role in early pregnancy establishment and adverse pregnancy outcomes.

Evidence Review

This review discusses unique uNK cell characteristics and presents clinical implications resulting from their dysfunction. We also systematically present existing knowledge about uNK cell function in three processes critical for successful human embryo implantation and placentation: stromal cell decidualization, spiral artery remodeling, and extravillous trophoblast invasion. Finally, we review the features of uNK cells that could help guide future investigations.

Results

It is clear the uNK cells are intimately involved in multiple facets of early pregnancy. This is accomplished directly, through the secretion of factors that regulate stromal cells and trophoblast function; and indirectly, via interaction with other maternal cell types present at the maternal-fetal interface. Current work also suggests that uNK cells are a heterogenous population, with subsets that potentially accomplish different functions.

Conclusion

Establishment of pregnancy through successful embryo implantation and placentation requires crosstalk between multiple maternal cell types and invading fetal trophoblast cells. Defects in this process have been associated with multiple adverse perinatal outcomes including hypertensive disorders of pregnancy, placenta accreta, and recurrent miscarriage though the mechanism underlying development of these defects remain unclear. Abnormalities in NK cell number and function which would disrupt physiological maternal-fetal crosstalk, could play a critical role in abnormal implantation and placentation. It is therefore imperative to dissect the unique physiological role of uNK cells in pregnancy and use this knowledge to inform clinical practice by determining how uNK cell dysfunction could lead to reproductive failure.

The decidual expression of Interleukin-7 is upregulated in early pregnancy loss

BACKGROUND

Maternal immunological rejection of the semi-allogenic fetus is discussed as one of the significant factors involved in early pregnancy loss. An array of cytokines secreted by both maternal and fetal cells is involved in generating a delicate maternal immune tolerance. Interleukin-7 (IL-7) is discussed to play a key role in pro-inflammatory processes, but there is still limited insight into the pathophysiological input on placentation and embryonic development in early pregnancy loss.

PATIENTS AND METHODS

Cytokine level differences were identified with quantitative real-time PCR in placental tissue from spontaneous abortions (SA) (n = 18), recurrent spontaneous abortions (RSA) (n = 15), and healthy pregnancies (n = 15) at gestational weeks 7 to 14. Protein expression of IL-7 in the decidua was investigated by immunohistochemistry. IL-7-expressing cells were identified with double-immunofluorescence.

RESULTS

Decidua of women with RSA expressed almost 51-times higher values of IL-7 in gene expression analysis. Immunohistochemistry identified a significant upregulation of IL-7 in the decidua of RSA specimens (p = .013) and in the decidua of women with SA (p = .004). Double-immunofluorescence confirmed decidual stroma cells as IL-7-expressing cells.

CONCLUSION

Significantly elevated IL-7 values in the decidua of spontaneous and recurrent miscarriages imply a crucial role of the cytokine in the signaling at the feto-maternal interface of the placenta. An overexpression of IL-7 could result in early pregnancy loss by inducing a pro-inflammatory environment. Proven to be valuable in other autoimmune diseases, targeting IL-7 signaling therapeutically may prove to be a very beneficial treatment option for RSA patients.

Time Course-Dependent Study on Equine Herpes Virus 9-Induced Abortion in Syrian Hamsters

Simple Summary

Equine herpesvirus 9 (EHV-9) is a virus belonging to the family of equine herpesviruses. EHV-9 has been isolated from natural infections of different wild and zoo animals. In addition, it has been associated with encephalitis and abortion in several animal species. However, the host range and pathogenesis of this virus are still unknown. Herein, we investigated the underlying pathogenesis of EHV-9-induced abortion in relation to the gestation period in either early or late trimester infection. We noticed that the late trimester infection of EHV-9 was associated with more severe death and both placental and fetal tissue localization of the virus. Also, early stage infection was accompanied by band necrotic changes within the placenta, which usually led to abortion.

Abstract

This study aimed to follow the time-course pathogenesis of EHV-9 abortion in early and late trimesters. Twenty-seven pregnant hamster dams were divided into three groups: (G1) control, (G2) EHV-9-inoculated on the 5th day (early trimester), and (G3) EHV-9-inoculated on the 10th day of gestation (late trimester). Dams were sacrificed at different time points during gestation and examined for viremia and viral DNA in different fetal and maternal tissues and pathological changes in fetal tissue, placenta, and cytokines. Animals in G3 showed a marked increase in the number of dead fetuses than those in G2. Histopathological findings of G2 showed early band coagulative necrosis of maternal spaces and stromal decidual cells. Necrotic changes were observed within the decidua basalis, spongiotrophoblast layer, and labyrinth. First, the virus was localized within mononuclear leukocytes in the decidua capsularis and basalis, and within the necrotic chorionic villi and cervical epithelium. G3 demonstrated degenerative changes within the chorionic villi and trophospongium. The virus antigen was observed within the chorionic villi, trophoblasts, mononuclear cells, and fetal tissues. In conclusion, EHV-9 induced abortion mostly occurs through necrosis of the chorionic villi and cannot cross through the capsular placenta in the early trimester but can through the developed decidual placentation.

IL-7/IL-7R signaling pathway might play a role in recurrent pregnancy losses by increasing inflammatory Th17 cells and decreasing Treg cells

PROBLEM

We aim to investigate a possible role of IL-7/IL-7R signaling pathway in recurrent pregnancy losses (RPL).

MATERIAL AND METHODS

Using the abortion-prone (AP) and non-abortion-prone (NP) mice model, fetal resorption rates (FRR), Th17 and Treg cells-related factors, and the effect of IL-7 and IL-7R antagonist were investigated by flow cytometry, quantitative real-time PCR, and immunohistochemistry. IL-7 and IL-7R expressions in human decidua were investigated by immunohistochemistry.

RESULTS

In the AP mice, IL-7R antagonist treatment significantly decreased FRR by downregulating Th17 and upregulating Treg-related factors. When the NP mice were treated with IL-7, FRR was significantly increased by upregulating Th17 and downregulating Treg-related factors. In decidual stromal cells of women with RPL, increased IL-7 and decreased IL-7R expressions were present when compared to normal controls.

CONCLUSION

IL-7/IL-7R signaling pathway plays a possible role in RPL by upregulating Th17 immunity, meanwhile downregulating Treg immunity. Regulation of IL-7/IL-7R may be a new therapeutic strategy for RPL.

Infertility and miscarriage: common pathways in manifestation and management

The relationship between miscarriage and fertility is complex. While most healthcare settings treat miscarriage as a problem of subfertility in assisted reproduction units, others believe that miscarriage occurs in super-fertile women. Infertile women undergoing assisted reproduction are at a greater risk of having a miscarriage especially at an advanced age compared with women conceiving naturally. Aberrant expression of immunological factors and chromosomal abnormalities underlie both infertility and miscarriage. Common risk factors include increased maternal age, obesity, smoking, alcohol, pre-existing medical conditions and anatomical abnormalities of the reproductive system. Management pathways of both conditions may be similar with pre-implantation genetic testing and assisted reproductive technology used in both conditions. This paper discusses the synergies and differences between the two conditions in terms of their epidemiology, etiopathogenesis, risk factors and management strategies. The two conditions are related as degrees of severity of reproductive failure with common pathways in manifestation and management.

Immune Reactivation by Cell-Free Fetal DNA in Healthy Pregnancies Re-Purposed to Target Tumors: Novel Checkpoint Inhibition in Cancer Therapeutics

The role of the immune system in cancer progression has become increasingly evident over the past decade. Chronic inflammation in the promotion of tumorigenesis is well established, and cancer-associated tolerance/immune evasion has long been appreciated. Recent developments of immunotherapies targeting cancer-associated inflammation and immune tolerance, such as cancer vaccines, cell therapies, neutralizing antibodies, and immune checkpoint inhibitors, have shown promising clinical results. However, despite significant therapeutic advances, most patients diagnosed with metastatic cancer still succumb to their malignancy. Treatments are often toxic, and the financial burden of novel therapies is significant. Thus, new methods for utilizing similar biological systems to compare complex biological processes can give us new hypotheses for combating cancer. One such approach is comparing trophoblastic growth and regulation to tumor invasion and immune escape. Novel concepts regarding immune activation in pregnancy, especially reactivation of the immune system at labor through toll like receptor engagement by fetal derived DNA, may be applicable to cancer immunotherapy. This review summarizes mechanisms of inflammation in cancer, current immunotherapies used in the clinic, and suggestions for looking beyond oncology for novel methods to reverse cancer-associated tolerance and immunologic exhaustion utilizing mechanisms encountered in normal human pregnancy.

Can Plateletcrit be a Marker for Recurrent Pregnancy Loss?

Aim:

To determine the utility of platelet (PLT) indices for the prediction of recurrent pregnancy loss (RPL).

Methods:

In all, 208 patients who experienced 2 or more first trimester spontaneous abortions and 95 controls who had no abortions were studied. The hematological markers, including plateletcrit (PCT) and neutrophil (Neu) to lymphocyte (Lym) ratio (NLR), were measured. Thrombophilia genetic tests for factor V Leiden mutation, prothrombin G202I0A mutation, and methylenetetrahydrofolate reductase C677 T and A1298C mutations were performed.

Results:

The PLT count, PCT, white blood cell count, red cell distribution width (RDW), Lym and Neu count, and NLR were significantly higher in patients with RPL than in controls. The RDW, PLT, and PCT values were higher in the low-risk group, whereas mean PLT volume values were lower than the high-risk group values.

Conclusion:

Plateletcrit is a low-cost, widely available marker for prediction of RPL in patients with a history of at least 1 abortus.

Elevation of soluble form of receptor for advanced glycation end products (sRAGE) in recurrent pregnancy losses (RPL): possible participation of RAGE in RPL

OBJECTIVE

To determine whether the soluble receptor for advanced glycation end products (sRAGE) and immune inflammatory markers are associated with recurrent pregnancy losses (RPL).

DESIGN

Prospective case-control study.

SETTING

University clinic.

PATIENT(S)

A total of 93 women (age 35.8±4.6 years) were enrolled including 63 women with three or more recurrent pregnancy losses (RPL), and age-matched fertile controls with a history of at least one live birth and no history of pregnancy losses (n=30).

INTERVENTION(S)

Peripheral blood collection.

MAIN OUTCOME MEASURE(S)

Assessment of anthropometric, metabolic, and inflammatory immune variables.

RESULT(S)

Levels of sRAGE were statistically significantly higher in RPL patients than in control patients (1,528.9±704.5 vs. 1,149.9±447.4 pg/mL). In the multivariate analysis, the levels of insulin, plasminogen activator inhibitor-1, the resistance index of the uterine radial artery, and the ratio of tumor necrosis factor-α/interleukin-10 producing T helper cells were statistically significantly associated with the serum sRAGE level.

CONCLUSION(S)

Elevated levels of serum sRAGE are associated with RPL. The soluble receptor for advanced glycation end products might contribute to RPL by reducing uterine blood flow and subsequently causing ischemia in the fetus via inflammatory and thrombotic reactions.

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.

Management of women with recurrent pregnancy losses and antiphospholipid antibody syndrome

Antiphospholipid antibodies (aPL) have been associated with recurrent pregnancy losses (RPL) and other obstetrical complications. The diagnostic criteria for the classical antiphospholipid antibody syndrome (APS) have been utilized for the detection of obstetrical APS in women with RPL. However, laboratory findings and immunopathology of obstetrical APS are significantly different from those of classical APS. In addition, many women with RPL who have positive aPL do not have symptoms consistent with the current APS criteria. The induction of a proinflammatory immune response from trophoblasts and complement activation by aPL rather than thromboembolic changes has been reported as a major immunopathological feature of obstetrical APS. Heparin treatment has been reported to be effective in prevention of early pregnancy loss with APS but not for the late pregnancy loss or complications. The complex effects of heparin may explain the limited efficacy of heparin treatment in RPL. New diagnostic criteria for obstetrical APS are needed urgently, and new therapeutic approaches should be explored further.

Commitment of decidual haematopoietic progenitor cells in first trimester pregnancy

PROBLEM  The aim of this study was to investigate the phenotype and commitment of decidual haematopoietic progenitor cells (HPCs) in healthy pregnant women and in women with early miscarriage. METHOD OF STUDY  Peripheral blood and decidual tissue from healthy and pathological pregnant women were examined for HPCs and lymphoid progenitors using flow cytometric analysis. RESULTS  Compared with peripheral blood, we found a significant increase in decidual HPCs in both healthy pregnant women and women with spontaneous abortion. T/NK, natural killer (NK), gamma-delta and NKT cell progenitors were identified in all peripheral blood and decidual samples. In pathologic pregnant women, the ratios of decidual T/NK and NK cell progenitors were significantly increased compared with healthy pregnant controls. CONCLUSION  We demonstrated decidual cells with haematopoietic progenitor cell phenotype in human decidua. Increased levels of NK progenitors in the decidua of women with early spontaneous abortion suggest a dysregulation of this pathway that may contribute to pregnancy failure.

Do uterine natural killer (uNK) cells contribute to female reproductive disorders?

The most abundant immune cells in the uterine decidua around the time of implantation and early placental development are the uterine natural killer (uNK) cells. Altered numbers of uNK cells have been associated with several human reproductive disorders, including recurrent miscarriage, recurrent implantation failure, uterine fibroids, sporadic miscarriage, fetal growth restriction and preeclampsia. Understanding of the function of uNK cells in non-pregnant and pregnant endometrium is now increasing; the potential contribution of altered numbers and function of uNK cells to reproductive disorders is the focus of this review.

Changes in endometrial natural killer cell expression of CD94, CD158a and CD158b are associated with infertility

PROBLEM

Cycle-dependent fluctuations in natural killer (NK) cell populations in endometrium and circulation may differ, contributing to unexplained infertility.

METHOD OF STUDY

NK cell phenotypes were determined by flow cytometry in endometrial biopsies and matched blood samples.

RESULTS

While circulating and endometrial T cell populations remained constant throughout the menstrual cycle in fertile and infertile women, circulating NK cells in infertile women increased during the secretory phase. However, increased expression of CD94, CD158b (secretory phase), and CD158a (proliferative phase) by endometrial NK cells from infertile women was observed. These changes were not reflected in the circulation.

CONCLUSION

In infertile women, changes in circulating NK cell percentages are found exclusively during the secretory phase and not in endometrium; cycle-related changes in NK receptor expression are observed only in infertile endometrium. While having exciting implications for understanding NK cell function in fertility, our data emphasize the difficulty in attaching diagnostic or prognostic significance to NK cell analyses in individual patients.

Clinical implication of natural killer cells and reproduction

The regulation of natural killer (NK) cells in the peripheral blood and endometrial layers has been associated with reproductive immunopathology such as recurrent spontaneous abortions (RSA), infertility of implantation failures, or pre-eclampsia. The placenta has a complex anatomical structure and different subsets of NK cells with various functional roles can directly interact with trophoblasts. NK cell subpopulations and their functions, putative roles of NK cells in peripheral blood and endometrium are reviewed in relation to RSA and infertility. An increase in NK cell numbers and /or activity in pre- or post-conceptional period in women with RSA or infertility with multiple implantation failures are a significant clinical concern. In addition, immuno-phenotypic characteristics of NK cells in these women support the changes for their increased activity status. Further studies are needed to explore underlying mechanism of NK cells in RSA, infertility, and other reproductive immunopathologies. Possible neurological and hormonal control of NK cells and NK cell interaction with various leukocyte populations need further investigation in women with reproductive failures.

How valuable is measurement of peripheral blood natural killer cells at the time of abortion?

PROBLEM

Increased peripheral blood natural killer (NK) cells are associated to immune-mediated abortion, but their diagnostic value when measured at the time of miscarriage is unknown.

METHOD OF STUDY

In women with therapeutic (A = 79) or elective (C = 34) pregnancy termination, the NK-cell percentage was measured before and 5 days after curettage. Additionally, immune-mediated lesions (scored 0-3) and CD56(+) and CD16(+) decidual NKs (scored 1-3) were detected on the abortion material.

RESULTS

Aborters differed from controls in histological scores (P = 0.000) and in NK percentage (>12%) only in the measurement 5 days after the operation (P = 0.038). In comparison to histological lesions, NK measurement was found to have sensitivity 70%, specificity 73.68%, positive prognostic value 89.39% and negative prognostic value 43.75%.

CONCLUSION

An Increased NK-cell percentage 5 days after the pregnancy termination could be a marker of immune aetiology of miscarriage, as the probability of an aborter with NK >12% to have an immune-mediated abortion is almost 90%.

Placental histopathologic features in patients with thrombophilic mutations

The purpose of this article is to review the histopathologic findings in the placenta of women with a known thrombophilic mutation. The findings range from normal to severe pathologic features including decidual vasculopathy, placental infarctions, syncytial knotting, maternal floor infarction, fetal thrombotic vasculopathy, vasculitis, and chronic villitis. They are, however, not pathognomonic of thrombophilic states, nor are necessarily markers of perinatal damage. The prospective evaluation of cases with known thrombophilic mutations and the application of tissue microarray examination of the placenta may allow identification of major histopathologic features and molecular parameters associated with maternal and/or fetal thrombophilic states. This may assist clinicians in their consultation with patients and optimize management in future pregnancies.

Placental pathology of recurrent spontaneous abortion: the role of histopathological examination of products of conception in routine clinical practice: a mini review

BACKGROUND

Histopathological examination of products of conception from miscarriages is part of routine clinical practice. The extent of additional clinically relevant information provided by this investigation in the setting of recurrent spontaneous abortion remains uncertain.

METHODS

Review of the literature was performed to identify studies reporting on findings of histological examination of routinely obtained products of conception in the setting of recurrent spontaneous abortion. The initial search identified 312 potential references, but 300 were excluded on further examination due to lack of data on specific histopathological findings in routine products of conception specimens from patients with recurrent spontaneous abortion. The 12 included studies indicated that such examination may identify hydatidiform moles, villous dysmorphic features suggesting fetal aneuploidy, chronic histiocytic intervillositis (CHI) and massive perivillous fibrin deposition and impaired trophoblast invasion. However, in most cases, morphological assessment cannot reliably determine the cause of the miscarriage or distinguish recurrent from sporadic miscarriage. Studies reporting on the use of additional immunohistochemical methods do not currently provide additional clinically useful diagnostic or prognostic information.

CONCLUSION

Routine histological examination of products of conception in the setting of recurrent spontaneous abortion can provide important clinical information in a minority of cases.

Lack of the appropriate natural killer cell inhibitory receptors in women with spontaneous abortion

Previous studies have revealed that women with unexplained recurrent spontaneous abortions have a limited repertoire of inhibitory KI receptors (inhKIRs) and that the inhKIRs they possess do not have specificity for the human leukocyte antigen (HLA)-Cw molecules that would be expressed on trophoblast. We sought to confirm these findings by direct definition of maternal inhKIR and trophoblastic HLA-Cw allotypes on the placental material of spontaneously missed pregnancies. The study included 30 women undergoing vacuum uterine curettage for first-trimester missed pregnancy (group A; n = 15) or for elective termination of normal pregnancy (group C, n = 15). DNA extracted from isolated decidual and trophoblastic cells was used for molecular detection of maternal inhKIRs (2DL1, 2DL2, 2DL3) and fetal HLA-Cw alleles, respectively. The results revealed that in the group of women who experienced abortion, 60% did not have the full repertoire of three inhKIRs (group A vs group C; p = 0.006); that in five of 15 patients (none in the controls), no epitope matching existed between maternal inhKIRs and trophoblastic HLA-Cw alleles (group A vs group C; p = 0.01); and that more cases were found with limited epitope matching (less than three inhKIRs with specificity for fetal HLA-Cw alleles). The results provide additional evidence that in some cases of spontaneous abortions, the women lack the appropriate inhKIRs to interact with the HLA-Cw molecules on trophoblasts and to deliver signals to inhibit natural killer cell activation and protect the embryo.

Preconception Peripheral Natural Killer Cell Activity as a Predictor of Pregnancy Outcome in Patients with Unexplained Infertility

PROBLEM

Preconception high peripheral natural killer (NK) cell activity in women with recurrent spontaneous abortion can predict subsequent miscarriages. We have examined prospectively, for the first time, the pregnancy rate in patients with unexplained infertility by measuring the peripheral NK activity.

METHOD OF STUDY

We tested the peripheral NK activity of 94 infertile women who despite treatment were unable to conceive for 6 or more months (mean; 2.4 years). Peripheral NK activity was measured by a chromium-51 release cytotoxicity assay. Women were followed for 2 years and assessed.

RESULTS

In 77 patients who were followed for 2 years, 28 had conceived but 49 did not. The peripheral NK activity of the group that became pregnant (mean +/- S.D.; 34.5 +/- 13.8%) was significantly lower than that of non-conception group (42.3 +/- 13.3%, P = 0.017).

CONCLUSIONS

Our finding suggests that elevated peripheral NK activity in patients with unexplained infertility is a risk factor for attaining pregnancy success.

Is there a place for immunomodulation in assisted reproduction techniques?

We briefly review the history of the concepts of the materno foetal relationship, and the (various) rationales which have been used to justify lymphocyte alloimmunisation (LA) as a treatment for recurrent spontaneous abortion of putative immune origins. The effectiveness of the treatment is at best dubious and limited to a small number of women for which there is no real positive selection rationale, at worst it is not efficient. The rationales themselves are rather "evolutive". The present one is to use the Th1:Th2 paradigm and, thus, to propose to "dampen NK activity" in abortion prone women and this concept has been extended by some to implantation failure. We briefly review why the Th1:Th2 paradigms is no longer fully valid, describe briefly why it is inappropriate for implantation, and conclude that alloimmunisation should no longer be proposed for RSA, hence, more for implantation failure. We, however, do not reject immunotherapy, but we believe that molecular and cellular defects specific approaches should be used, tailored for the specific pathway whose disruption cause the clinical symptom.

Should We Re-Examine the Status of Lymphocyte Alloimmunization Therapy for Recurrent Spontaneous Abortion?

PROBLEM

In the human, lymphocyte alloimmunization immunotherapy (IT) has been proposed as a treatment for recurrent spontaneous abortion (RSA). This treatment has been the subject of debate for a long period of time. Recently, it has been proposed to extend such a treatment for implantation failure in humans, and I was asked to express my opinion on this topic.

METHODS

I reviewed the evolution and theories and current paradigms in Reproductive Immunology and rationales proposed for IT. New discoveries show the complexity of implantation as a step by step developmental event, in mice and humans, and as such led me to re-examine paradigms currently evoked for extension of IT to implantation. Such a re-examination obviously leads me to re-question the basis of IT for RSA itself.

CONCLUSIONS

I conclude that the Th1/Th2 paradigm, evoked as the current basis for IT, and as useful as it has been to explain pregnancy, is no longer sufficient. It is especially insufficient to explain the process of implantation, which involves inflammatory molecules and cannot fit in such a scheme. It ensues that alloimmunization has no scientific rationale for the treatment of human implantation as a whole, and should not be applied broadly at such a stage of pregnancy. Furthermore, its use in RSA should be re-examined.

Fraction of the peripheral blood concentration of CD56+/CD16−/CD3− cells in total natural killer cells as an indication of fertility and infertility

OBJECTIVE

To determine whether the peripheral blood concentration of CD56(+)/CD16(-)/CD3(-) cells, the main natural killer (NK) subpopulation that colonizes the endometrium in the middle and late secretory phase, can be related to fertility or infertility status.

DESIGN

A case control study.

SETTING

Immunopathology department of an infertility laboratory.

PATIENTS

A total 99 women were selected (group I: consecutive spontaneous aborters, n = 25; group II: sporadic spontaneous aborters, n = 30; group III: infertile, n = 33; group IV: controls, n = 11).

INTERVENTION

Immunophenotyping of women grouped according to their fertility status.

MAIN OUTCOME MEASURES

Peripheral blood lymphocytes were examined by two- and three-color flow cytometry.

RESULTS

A statistically significant association between endometrial-type peripheral blood (PB) NK cell concentrations and fertility status (groups I and IV vs. groups II and III) was documented. The %(/TOTAL PB)(CD56+CD16-CD3-) NK cells was significantly higher [1] in fertile (groups I and IV) than in sporadic aborters/infertile (groups II and III) women, [2] in group I when compared with groups II and III, and [3] in group IV when compared with groups II and III.

CONCLUSIONS

This study indicates that diminished numbers of the %(/TOTAL PB)(CD56+CD16-CD3-) NK cells are related to sporadic aborters and infertile women. Thus, the fraction could be used as an indicator of subsequent successful implantation and maintenance of gestation.

Natural killer (NK) cell receptors' repertoire in couples with recurrent spontaneous abortions

PROBLEM

Natural killer (NK) cell receptors (NKRs) have been suggested to protect trophoblast, but their function at the fetomaternal interface remains unknown. To investigate if the outcome of pregnancy depends on women's NKRs, we studied the NKR repertoire in couples with recurrent spontaneous abortions (RSA).

METHODS

Twenty-six childless couples with > or = 2 abortions, characterized by alloimmune abnormalities, and 26 control couples were genotyped for five killer immunoglobulin-like receptors (KIR) and two CD94/NKG receptors, known to have as ligands human leukocyte antigen (HLA) class I molecules with trophoblastic expression: inhibitory 2DL1,2,3 and activating 2DS1,4 KIRs, inhibitory NKG2A and activating NKG2C. Detected repertoires of women and partners were compared between the two groups.

RESULTS

Less aborters than controls were found to have all three inhibitory KIRs (30.77% versus 69.23%, P = 0.01), some of them had only one inhibitory KIR (19.23% versus 3.85%, P = 0.08) and most of them were lacking inhibitory KIRs possessed by their husbands (57.69% versus 15.38%, P = 0.001).

CONCLUSIONS

Women with alloimmune abortions have a limited inhibiting KIR repertoire and such miscarriages may occur because trophoblastic HLA class I molecules are recognized by decidual NK cells lacking the appropriate inhibitory KIRs.

Effect of intravenous immunoglobulin treatment on the Th1/Th2 balance in women with recurrent spontaneous abortions

PROBLEM

The way by which intravenous immunoglobulin (IvIg) acts to prevent immunlogically mediated recurrent spontaneous abortions (RSA) has not been clarified. In the present study, a possible effect of IvIg on the T helper cell (Th1/Th2) balance was investigated in abortions of either alloimmune or autoimmune abnormalities.

METHOD OF STUDY

The study included 21 women treated with IvIg before conception because of a history of RSA characterized by alloimmune abnormalities (n = 15) or associated with anti-phospholipid antibodies (APA) (n = 6). Peripheral blood samples, collected before and 5 days after the first IvIg infusion, were stimulated, and Th1 and Th2 cells were detected by flow-cytometric analysis using a combination of monoclonal antibodies against T-cell surface markers and intracellular interferon (IFN)-gamma and interleukin (IL)-4. The percentage of IFN-gamma-producing (Th1) and IL-4-producing (Th2) cells and the Th1/Th2 ratio were compared between pre- and post-infusion samples.

RESULTS

A decrease of Th1 percentage in 66.6% of the cases and a concurrent Th2 percentage increase (47.61%) resulted in a decrease in the Th1/Th2 ratio in most of the cases (76.1%) (p < 0.01). Similar results were found in Group A (Th1/Th2 decreased in 60% of the cases, p < 0.05), while in Group B the effect of IvIg was not clear (Th1/Th2 increased in three and decreased in another three cases).

CONCLUSION

Our finding suggests that IvIg administration in women with alloimmune RSA enhances Th2 polarization. This is not always the case with APA-associated abortions.

Glycodelin: a major lipocalin protein of the reproductive axis with diverse actions in cell recognition and differentiation

Glycodelin is a glycoprotein that belongs to the lipocalin superfamily. Depending on glycosylation, glycodelin appears in various isoforms. In the uterus, glycodelin-A is the major progesterone-regulated glycoprotein secreted into uterine luminal cavity by secretory/decidualized endometrial glands. The other tissues expressing glycodelin include fallopian tubes, ovary, breast, seminal vesicle, bone marrow, and eccrine glands. Glycodelin-A potently and dose-dependently inhibits human sperm-egg binding, whereas differently glycosylated glycodelin-S from seminal plasma has no such effect. Absence of contraceptive glycodelin-A in the uterus during periovulatory midcycle is consistent with an open "fertile window." Glycodelin induced by local or systemic administration of progestogens may potentially reduce the fertilizing capacity of sperm in any phase of the menstrual cycle. Glycodelin also has immunosuppressive activity. Its high concentration at the fetomaternal interface may contribute to protection of the embryonic semiallograft. Besides being an epithelial differentiation marker, glycodelin appears to play a role in glandular morphogenesis, as transfection of glycodelin cDNA into a glycodelin-negative breast cancer cells resulted in formation of gland-like structures, restricted proliferation, and induction of other epithelial markers. These various properties, as well as the chemistry, biology, and clinical aspects of glycodelin, continue to be areas of active investigation reviewed in this communication.

Deficiency of decidual IL-10 in first trimester missed abortion: a lack of correlation with the decidual immune cell profile

PROBLEM

To determine if first trimester missed abortion decidua is characterized by an altered immune cell profile and/or a modified interleukin (IL)-10 and interferon (IFN)-gamma production pattern compared with decidua from elective termination.

METHOD OF STUDY

Flow cytometry and immunohistochemistry techniques were used to determine the decidual immune cell phenotypic profile and production pattern of IL-10 and IFN-gamma in cases of elective termination (n = 14) and missed abortion (n = 12).

RESULTS

Both groups had a similar proportion of CD56+ CD16-, CD56+ CD16+, CD19+, CD3+, CD4+, CD8+, alphabeta T cells and gammadelta T cells. The majority of alphabeta and gammadelta positive T cells in both groups coexpressed the natural killer (NK) cell marker CD56, but lacked cell surface expression of CD3. Diminished decidual IL-10 staining was noted in 7/10 missed abortion cases compared with none of the elective termination cases (n = 12) (P = 0.007). A uniform decidual IFN-gamma staining pattern was observed in both groups.

CONCLUSION

Decreased IL-10 production coupled with a sustained IFN-gamma presence noted in missed abortion compared with elective termination cases suggest that these cytokines may be important determinants in pregnancy outcome. In contrast, differences in the proportion of immune cells between both groups may not be a critical factor in early pregnancy loss. In normal pregnancy, decidual alphabeta and gammadelta positive T cells with reduced CD3 on their cell surface may be intrinsically restricted in T-cell receptor (TCR)-mediated activation.