Future directions of studies for recurrent miscarriage associated with immune etiologies

Successful Pregnancy and Delivery at Term Following Intravenous Immunoglobulin Therapy with Heparin for Unexplained Recurrent Pregnancy Loss Suspected of Immunological Abnormalities: A Case Report and Brief Literature Review

About 60% of cases of recurrent pregnancy loss have unexplained etiology. Immunotherapy for unexplained recurrent pregnancy loss is still unestablished. A 36-year-old woman, not obese, had a stillbirth at 22 gestational weeks and a spontaneous abortion at 8 weeks. She had been examined for recurrent pregnancy loss at previous clinics with no significant findings. When she visited our clinic, a hematologic test showed a Th1/Th2 ratio imbalance. Ultrasonography, hysteroscopy, and semen analysis showed no abnormalities. She successfully conceived by embryo transfer in hormone replacement therapy cycle. However, she had a miscarriage at 19 weeks. The baby had no deformities, but a chromosomal test was not performed, according to the parents' will. The placenta pathologically suggested hemoperfusion problems. Her and her husband's chromosomal tests showed normal karyotypes. Other examinations revealed a repeated Th1/Th2 ratio imbalance and a high resistance index of uterine radial artery blood flow. She was administered low-dose aspirin, intravenous immunoglobulin, and unfractionated heparin after the second embryo was transferred. Her baby was healthily born by cesarean section at 40 weeks. Intravenous immunoglobulin therapy can be a choice for recurrent miscarriage without risk factors because it has clinically beneficial influences on the patient's immunological aberration.

Decreased Production of TNF-α and IL-6 Inflammatory Cytokines in Non-Pregnant Idiopathic RPL Women Immunomodulatory Effect of Sildenafil Citrate on the Cellular Response of Idiopathic RPL Women

Sildenafil citrate (SC), a PDE5 inhibitor, a drug for erectile dysfunction (ED) and pulmonary hypertension (PAH), was found to exert a positive effect on pregnancy outcomes when administered intravaginally before conception. In our previous studies, sildenafil increased endometrial thickness and significantly decreased peripheral blood NK cell activity after the intravaginal administration in women with recurrent pregnancy loss (RPL). No data are available to confirm the effect of sildenafil on maternal T cell populations involved in shaping fetal-maternal tolerance and NK cell activity. Thus, the present study aimed to establish if SC influences NKT cells or the axis of Th17/Treg cells and Th1/Th2 cytokine production. Materials and methods: Twenty-one healthy fertile women and twenty-two nonpregnant women with idiopathic RPL were studied. The ELISA method was used to evaluate the production of cytokines, including IL-2, IL-12p40, IL-4, IL-10, IL-6, IL-17, IL-21, TGF-β, TNF-α, and IFN-γ in PBMC culture supernatants before and after supplementation with the physiological concentration of SC. The percentages of NKT (CD56⁺CD3⁺CD44⁺CD161⁺), Treg (CD4⁺CD25⁺FOXP3⁺) and Th17 (CD4⁺CD25⁺IL-17A⁺) cells were determined with flow cytometry method. Results: Unexpectedly, we found that the PBMCs of patients with RPL produced a significantly lower level of inflammatory cytokines (TNF-α and IL-6) and a higher level of anti-inflammatory cytokines (TGF-β and IL-10). SC significantly decreased IL-6, IL-12 and increased TGF-β cytokine concentration in fertile women. In the case of RPL patients’ PBMCs, SC improved the production of TNF-α and IL-10. Conclusions: Lower concentration of proinflammatory cytokines in idiopathic RPL women compared to fertile women might suggest the exhaustion of the immune system. The emphasized production of IL-10 by SC partially explains the previously observed downregulation of NK cell activity in RPL patients. The immunomodulatory effect of the drug might be utilized in anti-inflammatory therapies and help achieve positive pregnancy outcomes in women with reproductive failure due to a Th1/Th2 imbalance.

The Role of Immune Cells in Recurrent Spontaneous Abortion

Recurrent spontaneous abortion affects approximately 1–2% of women of childbearing, and describes a condition in which women suffer from three or more continuous spontaneous miscarriages. However, the origin of recurrent spontaneous abortion (RSA) remains unknown, preventing effective treatment and placing stress upon patients. It has been acknowledged that successful pregnancy necessitates balanced immune responses. Therefore, immunological aberrancy may be considered a root cause of poor pregnancy outcomes. Considerable published studies have investigated the relationship between various immune cells and RSA. Here, we review current knowledge on this area, and discuss the five main categories of immune cells involved in RSA; these include innate lymphocytes (ILC), macrophages, decidual dendritic cells (DCs), and T cells. Furthermore, we sought to summarize the impact of the multiple interactions of various immune cells on the emergence of RSA. A good understanding of pregnancy-induced immunological alterations could reveal new therapeutic strategies for favorable pregnancy outcomes.

The Endometrial Immune Profiling May Positively Affect the Management of Recurrent Pregnancy Loss

Introduction

The endometrial immune profiling is an innovative approach based on the analysis of the local immune reaction occurring in the endometrium at the time of the embryo implantation. By documenting the local immune activation during the period of uterine receptivity, we aim to detect and correct potential imbalances before and at the very beginning of placentation. The main objective of the study was to analyze in women with a history of repeated pregnancy loss (RPL) the association of personalized strategies based on immune dysregulations with live birth rates. The secondary objective was to highlight the main prognostic factors for live births.

Methods

This is an observational retrospective analysis of 104 patients with RPL, included between January 2012 and December 2019. Inclusion criteria included a spontaneous fertility with at least three miscarriages, an assessment including a three-dimension ultrasound scan, an endometrial biopsy for uterine immune profiling and a follow-up over at least 6 months with personalized care if indicated after the complete assessment. We defined as a success if the patients had a live birth after the suggested plan, as a failure if the patient either did not get pregnant or experienced a new miscarriage after the targeted therapies.

Results

Uterine immune profiling was the only exploration to be significantly associated with a higher live birth rate (LBR) if a dysregulation was identified and treated accordingly (55% vs 45%, p=0.01). On the contrary, an absence of local dysregulation (resulting in an apparently balanced immune environment) was associated with a higher risk of a new miscarriage, suggesting that the cause inducing RPL still needed to be identified. Independently of age and AMH level, dysregulated immune profile is significatively associated with 3 times higher LBR than a non-deregulated profile (OR=3.4 CI 95%1.27-9.84) or five times in case of an overactive profile treated by immunotherapy (OR=5 CI 95% 1.65-16.5). The usage of ART was significantly associated with lower LBR regardless of the presence of a subfertility factor (p=0.012). Personalization of medical care using natural cycle or simple hormonal stimulation is associated with a significantly higher LBR than personalization including ART treatments regardless of maternal age and AMH level (OR= 2.9 CI 95% 1.03-8.88).

Conclusion

Our study suggests that some endometrial immune profiles with targeted management of RPL are associated with a higher rate of LBR. ART may be negatively associated with LBR.

Alteration in endometrial helper T-cell subgroups in chronic endometritis

PROBLEM

The effect of chronic endometritis (CE) on the subpopulation of CD4⁺ T cells, Th1, Th2, Th17, and regulatory T cells in the endometrium is unknown.

METHOD OF STUDY

Lymphocytes were isolated from the endometrium of CE patients (n = 12) and non-CE patients (n = 7). The CD4⁺ T-cell profile was analyzed by flow cytometry and immunofluorescence.

RESULTS

In the endometrium of CE patients, there were significantly more Th1 cells among CD4⁺ cells and fewer Th2 cells in comparison to non-CE patients. No marked difference was observed in Th17 cells or Foxp3⁺ Treg cells. Moreover, the proportion of Th1 cells increased and the proportion of Th2 cells decreased as the number of CD138⁺ cells increased. Furthermore, when the localization of CD138⁺ cells and CD4⁺ cells was examined, CD4⁺ cells were found to be clustered around CD138⁺ cells in CE patients.

CONCLUSION

The CD4⁺ T-cell profile in the endometrium is altered in women with CE. This finding may help to clarify the pathophysiology and development of treatment methods for CE.

Successful Pregnancy in a Case of Behçet's Disease after Treatment with Prednisolone

A 34-year-old woman (gravida 1, para 0) visited the Division of Reproductive Medicine/National Center for Child Health and Development due to infertility; she had also been suffering from incompletely treated genital ulcers and stomatitis for 10 years. This case was diagnosed as an incomplete-type Behçet's disease (BD) at the Department of Maternal-Fetal Biology/National Center for Child Health and Development. Since no apparent abnormality was found in the general infertility test, artificial insemination with the husband's semen (AIH) was performed for the patient with unexplained infertility, which failed. However, after treating BD with prednisolone, chronic inflammation (stomatitis and genital ulcer) and immunological abnormalities (Th2 and NK cell activity) improved, and conception was possible by AIH. Thus, prednisolone administration may have induced immune tolerance in the patient with BD, which may have contributed to the success of AIH.

A semen-based stimulation method to analyze cytokine production by uterine CD56bright natural killer cells in women with recurrent pregnancy loss

Cytokine secretion by NK cells is abnormal in some women with recurrent pregnancy loss (RPL). Cytokine production is usually evaluated after stimulation with PMA and ionomycin. However, stimulation of uterine NK cells with semen corresponds more closely to physiological conditions at the time of conception. As seminal plasma has immunomodulatory properties, we aimed to elucidate compatibility between uterine NK cells and semen. Endometrial samples were stimulated with PMA/ionomycin, semen, seminal plasma, or spermatozoa. Thereafter, cytokine production by NK (CD56^bright) cells was evaluated using flow cytometry and compared between women with and without a history of RPL associated with abnormal NK cell distribution in the endometrium or unexplained RPL. The ratios (%) of NK cells producing IFN-γ and TNF-α (NK1 phenotype), IL-4 (NK1/NK2 phenotype), and IL-10 (NK1/NKr1 phenotype) were significantly lower after stimulation with semen than with PMA/ionomycin (P < 0.01). After exposure to semen, ratios (%) of NK cells producing IL-4 and IL-10 in patients with unexplained RPL were significantly lower (P < 0.05), whereas those of NK1/NK2 and NK1/NKr1 were significantly higher (P < 0.01) than those in controls. The shift of endometrial NK cells to the NK2 phenotype was more pronounced when stimulated by semen than by PMA/ionomycin. However, a semen-induced shift to NK1 in women with unexplained RPL could induce miscarriage. Couple-specific immunological compatibility tests through semen stimulation in vitro might provide important information to avoid RPL.

Beyond Uterine Natural Killer Cell Numbers in Unexplained Recurrent Pregnancy Loss: Combined Analysis of CD45, CD56, CD16, CD57, and CD138

Changes in the number and cytotoxic potential of uterine Natural Killer (uNK) cells have been associated with reduced fertility. To provide a better characterization of immunophenotypes in the endometrium of women with uRPL (unexplained recurrent pregnancy loss), we examined the applicability of a set of five immune cell markers. The concentration (cells/mm²) of CD45⁺ leukocytes, CD56⁺ uNK cells, and CD138⁺ plasma cells as well as of CD16⁺ and CD57⁺ cells, which indicate high cytotoxic uNK cells, were assessed by immunohistochemistry in endometrial biopsies from 61 uRPL patients and 10 controls. Control fertile endometria presented 90-300 CD56⁺ uNK cells/mm². uRPL cases were classified in subgroups of low (uRPL-CD56^low < 90 cells/mm²), normal (uRPL-CD56^normal 90-300 cells/mm²), and high uNK cell counts (uRPL-CD56^high > 300 cells/mm²). Some cases from the uRPL-CD56^low and uRPL-CD56^normal subgroups showed elevated proportions of cytotoxic CD16⁺ and CD57⁺ cells in relation to CD56⁺ cells. In the uRPL-CD56^high subgroup, the CD57/CD56 ratio was reduced in most samples and the CD16/CD56 ratio was unaltered. Analysis of CD138 excluded the influence of chronic endometritis on these observations. Our results reinforce a link between uRPL and a dysfunctional endometrial environment associated with distinct immune cell profiles.

Tregitopes regulate the tolerogenic immune response and decrease the foetal death rate in abortion-prone mouse matings

The imbalance in immune tolerance may cause the variety of reproductive failures. An intravenous immunoglobulin infusion (IVIg) therapy is used to improve the live birth rate in women suffering from recurrent pregnancy loss, recurrent spontaneous abortions and recurrent implantation failures. However, the results of IVIg studies are still inconclusive as IVIg infusion in women suffering from pregnancy loss is sometimes ineffective. One of the mechanisms of action of this treatment is inhibition of B cells differentiation and expansion of Tregs and secretion of interleukin 10. It was proposed that immunomodulatory effects of IVIg may be attributed to tregitopes - self-IgG-derived epitopes present in the structure of immunoglobulins. Similarly to IVIg, tregitopes cause the expansion of Tregs and secretion of antigen-specific effector cytokine response. Here, we studied whether the administration of mouse tregitope 167 and/or 289 can prevent abortions in mouse abortion-prone mouse matings. We revealed that tregitopes reduce the foetal death rate. This may be driven by observed higher pool of peripheral Tregs, increased production of IL-10 by Tregs and Bregs and/or maintaining the tolerogenic phenotype of antigen-presenting cells. We believe that our findings may indicate a potential alternative to IVIg for therapeutic intervention in case of pregnancy failures.

Expression of retinoid-related orphan receptor (ROR)γt on NK22 cells in the peripheral blood and uterine endometrium of women with unexplained recurrent pregnancy loss and unexplained infertility

AIM

Recently, NK22 cells, a subset of interleukin (IL)-22-producing natural killer (NK) cells, were identified. We have previously reported the higher percentage of NK22 cells in women suffering recurrent pregnancy loss (RPL). Moreover, we have also reported lower expression of NKp46, a kind of natural cytotoxicity receptor (NCR), on NK cells and the changes of NK cell producing cytokines in women who experience RPL. NK22 cells express NCRs, such as NKp44 or NKp46. Retinoid-related orphan receptor γt (RORγt) is known as a regulator of NK22 cells; however, in NK22 cells of peripheral blood (PB) and the uterine endometrium (UE), the relationship between NCRs and RORγt is unclear. We investigate RORγt expression NK22 cells in the PB and UE of women with unexplained infertility (uI) or unexplained RPL (uRPL).

METHODS

Lymphocytes were extracted from PB and UE, derived from women with uI or uRPL. Expression of RORγt and NCRs in NK cells and NK cell-produced cytokines were analyzed by flow cytometry.

RESULTS

CD56+ /NKp46+ /RORγt+ cells were positively correlated with CD56+ /IL-22+ cells in both PB and UE. CD56bright /NKp46bright /RORγt+ cells were significantly higher in uRPL than in uI, and endometrial CD56bright /NKp46bright /RORγt+ cells were positively correlated with PB. In UE, CD56bright /RORγt+ cells were negatively correlated with CD56bright /interferon-γ+ and CD56bright /tumor necrosis factor-α+ cells of uRPL.

CONCLUSION

RORγt may be associated with NK22 cells in reproduction. Particularly, higher expression of RORγt may be associated with elevated NK22 cells in uRPL.

Peripheral blood natural killer cells and mild thyroid abnormalities in women with reproductive failure

Abnormalities in peripheral blood natural killer (NK) cells have been reported in women with primary infertility and recurrent spontaneous abortion (RSA) and several studies have been presented to define cutoff values for abnormal peripheral blood NK cell levels in this context. Elevated levels of NK cells were observed in infertile/RSA women in the presence of thyroid autoimmunity (TAI), while no studies have been carried out, to date, on NK cells in infertile/RSA women with non-autoimmune thyroid diseases. The contribution of this study is two-fold: (1) the evaluation of peripheral blood NK cell levels in a cohort of infertile/RSA women, in order to confirm related data from the literature; and (2) the assessment of NK cell levels in the presence of both TAI and subclinical hypothyroidism (SCH) in order to explore the possibility that the association between NK cells and thyroid function is not only restricted to TAI but also to SCH. In a retrospective study, 259 age-matched women (primary infertility [n = 49], primary RSA [n = 145], and secondary RSA [n = 65]) were evaluated for CD56+CD16+NK cells by flow cytometry. Women were stratified according to thyroid status: TAI, SCH, and without thyroid diseases (ET). Fertile women (n = 45) were used as controls. Infertile/RSA women showed higher mean NK cell levels than controls. The cutoff value determining the abnormal NK cell levels resulted ⩾15% in all the groups of women. Among the infertile/RSA women, SCH resulted the most frequently associated thyroid disorder while no difference resulted in the prevalence of TAI and ET women between patients and controls. A higher prevalence of women with NK cell levels ⩾15% was observed in infertile/RSA women with SCH when compared to TAI/ET women. According to our data, NK cell assessment could be used as a diagnostic tool in women with reproductive failure and we suggest that the possible association between NK cell levels and thyroid function can be described not only in the presence of TAI but also in the presence of non-autoimmune thyroid disorders.

Evidence-based management of recurrent miscarriages

Recurrent miscarriages are postimplantation failures in natural conception; they are also termed as habitual abortions or recurrent pregnancy losses. Recurrent pregnancy loss is disheartening to the couple and to the treating clinician. There has been a wide range of research from aetiology to management of recurrent pregnancy loss. It is one of the most debated topic among clinicians and academics. The ideal management is unanswered. This review is aimed to produce an evidence-based guidance on clinical management of recurrent miscarriage. The review is structured to be clinically relevant. We have searched electronic databases (PubMed and Embase) using different key words. We have combined the searches and arranged them with the hierarchy of evidences. We have critically appraised the evidence to produce a concise answer for clinical practice. We have graded the evidence from level I to V on which these recommendations are based.

Role of HLA-G and other immune mechanisms in pregnancy

Pregnancy loss (abortion) and pre-eclampsia represent the most common disorders in pregnant women. Besides infection, there are anatomical, endocrinological, genetic and immunological factors that can induce pregnancy disorders. Because the exact mechanisms of physiological pregnancy maintenance are still not clearly understood, the search for genes and proteins fulfilling this role is still in progress. One of the immune molecules that plays a beneficial role in pregnancy is the nonclassical HLA-G molecule. The molecule is mainly expressed on trophoblast cells in the foetal placenta and induces the immune tolerance of the foetus via its interaction with inhibitory receptors on maternal NK cells and CD8+ T lymphocytes. In relation to pregnancy disorders, associations between HLA-G polymorphism, HLA-G level and HLA-G function were described. Thus, the HLA-G molecule can be used as a new diagnostic marker and, potentially, for the future therapy of pregnancy disorders.