Maternal-Fetal Compatibility in Recurrent Pregnancy Loss.

Nowadays, recurrent pregnancy loss (RPL) is an undesirable condition suffered by many patients of reproductive age. In this scenario, certain immune cell populations and molecules, involved in maternal-fetal compatibility, have emerged as factors related with the pathogenesis of RPL. Among them, uterine Natural Killer cells (uNKs) appear to be of great relevance. These cells are involved in numerous processes during pregnancy, such as the remodeling of uterine spiral arteries or the control of trophoblast invasion. These functions are regulated by the interactions that these cells establish with the extravillous trophoblast, mainly through their Killer Immunoglobulin-like Receptors (KIRs) and the Human Leukocyte Antigen-C (HLA-C) molecules expressed by the embryo. A high level of polymorphism has been reported for both molecules involved in this interaction, with some of the possible KIR-HLA-C combinations being associated with an increased risk of RPL. However, the complexity of the maternal-fetal interface goes beyond this, as other HLA molecules also appear to be related to this reproductive pathology. In this review, we will discuss the role of uNKs in pregnancy, as well as the polymorphisms and clinical implications of KIR-HLA-C binding. We will also address the involvement of other, different HLA molecules in RPL, and the current advice on the appropriate management of patients with 'immunological mismatch', thus covering the main aspects regarding the involvement of maternal-fetal compatibility in RPL.

New insights into decidualization: immunological and genetic factors.

PURPOSE OF REVIEW: Nowadays, there are many efforts focused on improving embryo quality for assisted reproduction treatments. Nevertheless, there are important maternal aspects, such as decidualization, also essential for pregnancy, often forgotten. With this review, we intend to highlight the main events involved in this endometrial phenomenon, as well as the cells and molecules that have recently been related to it. RECENT FINDINGS: Decidualization entails a complete transformation of the endometrium, with recent research reaffirming progesterone as its main molecular trigger. Certain immune components and membrane molecules have also been found to play a role in it, notably the killer immunoglobulin-like receptors (KIR) of uterine natural killer (uNK) cells, as well as the human leukocyte antigen (HLA)-F. SUMMARY: Progesterone directs the cellular changes that take place during decidualization, as well as the recruitment and maturation of uNKs, along with the coordinated action of interleukin-15. Likewise, the role of KIR and HLA-F in this process and in the subsequent development of pregnancy is being highlighted in many studies, with effects on reproductive outcomes related to the different genotypes of these molecules.

Increased cytotoxic natural killer cells in the endometrium alone cannot be considered the immunological cause of recurrent miscarriage.

OBJECTIVE: To study the distribution and gene expression of endometrial immune cell populations, especially natural killer (NK) subsets, between assisted reproductive technology patients and healthy donors and explore a possible relationship of these results with patients' killer cell immunoglobulin-like receptor (KIR) genotypes and KIR-human antigen leukocyte-C (HLA-C) binding. DESIGN: Prospective observational cohort study. SETTING: Clinic and university laboratories. PATIENT(S): Participants included 39 women with recurrent miscarriages who had undergone in vitro fertilization cycles with donated oocytes and 21 healthy oocyte donors with proven fertility. INTERVENTION(S): Endometrial biopsy samples were collected from both patients and donors, and the KIR genotypes of the assisted reproductive technology patients were analyzed. MAIN OUTCOME MEASURE(S): Endometrial gene expression (cluster of differentiation [CD] antigens and anti-inflammatory and proinflammatory interleukins) and the number and percentage of regulatory T and NK cell populations in patients and donors were determined. Subsequently, the results obtained were categorized in the group of patients by KIR genotype. Killer cell immunoglobulin-like receptor-HLA-C binding was also examined in patients, considering their KIRs. RESULT(S): A higher percentage of CD56dimCD16+ NK cells were observed in patients than those in healthy donors. Nevertheless, when categorizing patients by KIR genotype and comparing the KIR AA (35.9%), AB (43.6%), and BB (20.5%) groups, no statistically significant difference was observed in either endometrial gene expression or any of the immune cell populations analyzed. Finally, no differences in binding between KIR and HLA-C molecules were registered among these 3 sets of patients. CONCLUSION(S): The reported increase in the number of NK cells with a cytotoxic profile in the endometrium of women with a history of recurrent miscarriages cannot alone explain these events because no relationship is observed between such cellular increase and the KIR genotypes, which individually, and in combination with the different HLA-C alleles, have also been associated, by previous studies, with negative reproductive outcomes. CLINICAL TRIAL REGISTRATION NUMBER: 1405-MAD-025-JG.

Adjustment of progesterone administration after endometrial transcriptomic analysis does not improve reproductive outcomes in women with adenomyosis.

RESEARCH QUESTION: Do patients with adenomyosis present a dysregulated endometrial receptivity that can be reversed with personalized embryo transfer (PET) by transcriptomic-based progesterone adjustment, improving IVF outcomes? DESIGN: A multicentre, retrospective, cohort study that transcriptomically analysed the endometrial receptivity of the endometrium in patients with adenomyosis (n = 81) and healthy women (n = 231). Subsequently, implantation, biochemical and clinical miscarriage, and live birth rates between adenomyosis patients with one previous implantation failure using donor oocytes who received (n = 59) or did not receive (n = 66) PET based on endometrial receptivity, were observed to evaluate if adjusted progesterone improves reproductive outcomes of adenomyosis patients. RESULTS: Patients with adenomyosis significantly presented an altered endometrial receptivity (non-receptive) compared with healthy patients (53.1% versus 37.2%, P = 0.0179), elevating the risk of adenomyosis patients having a non-receptive endometrium 42.59% higher (95% CI 41.50 to 44.45). No significant differences were found in implantation (62.7% versus 78.8%, P = 0.0514), biochemical (13.5% versus 3.9%, P = 0.1223) and clinical (10.8% versus 15.4%, P = 0.7543) miscarriage, or live birth rates (75.7% versus 80.8%, P = 0.6066), in patients with PET compared with those without PET. CONCLUSIONS: Women with adenomyosis presented an altered expression of genes involved in decidualization, and a higher rate of non-receptive endometrial statuses than controls. Although progesterone is indispensable for implantation, adjusting progesterone before PET, using endometrial transcriptomic signatures, does not improve IVF outcomes in patients with adenomyosis. Other molecular mechanisms beyond progesterone regulation may be involved in implantation failure.

A review of the pathophysiology of recurrent implantation failure.

Implantation is a critical step in human reproduction. The success of this step is dependent on a competent blastocyst, receptive endometrium, and successful cross talk between the embryonic and maternal interfaces. Recurrent implantation failure is the lack of implantation after the transfer of several embryo transfers. As the success of in vitro fertilization has increased and failures have become more unacceptable for patients and providers, the literature on recurrent implantation failure has increased. While this clinical phenomenon is often encountered, there is not a universally agreed-on definition-something addressed in an earlier portion of this Views and Reviews. Implantation failure can result from several different factors. In this review, we discuss factors including the maternal immune system, genetics of the embryo and parents, anatomic factors, hematologic factors, reproductive tract microbiome, and endocrine milieu, which factors into embryo and endometrial synchrony. These potential causes are at various stages of research and not all have clear implications or immediately apparent treatment.

Immunologic causes and thrombophilia in recurrent pregnancy loss.

Certain miscarriages result from immunologic factors, but there is no clear identification of the precise causes of recurrent pregnancy loss (RPL). Miscarriages and RPL can arise from a disruption of maternal-fetal immune homeostasis. Remodeling of the maternal uterine spiral arteries is one of the key steps for normal growth and development of the fetus. An adequate oxygen supply is necessary for correct placentation, and it is accomplished by proper vascular changes. The development of fetal tissues creates a potential immunologic problem since the fetus can express paternal antigens and, in some cases, antigens of a gamete donor. The maternal immune system actively responds to fetal antigens, and dysregulation of this crosstalk could partly explain pregnancy complications such as miscarriages and RPL. RPL resulting from thrombophilia is primarily due to acquired thrombophilia, and therefore screening and treatment should be focused on antiphospholipid antibody syndrome.

Uterine natural killer cells: from foe to friend in reproduction.

BACKGROUND: Recurrent miscarriage and pre-eclampsia are common reproductive disorders, but their causes are often unknown. Recent evidence has provided new insight into immune system influences in reproductive disorders. A subset of lymphocytes of the innate immune system known as uterine natural killer (uNK) cells are now recognized as fundamental to achieving embryo implantation and successful pregnancy, but were initially attributed a bad reputation. Indeed, immune therapies have been developed to treat the 'exaggerated' immune response from uNK cells. These treatments have been based on studies of peripheral blood natural killer (pbNK) cells. However, uNK cells and pbNK cells have different phenotypic and functional characteristics. The functions of uNK cells are closely related to their interactions with the extravillous trophoblast cells (EVTs) and spiral arteries, which underlie an essential role in regulating vascular function, controlling trophoblast invasion and promoting placental development. EVTs express MHC molecules of class I HLA-C/E/G/F, while uNK cells express, among other receptors, killer cell immunoglobulin-like receptors (KIRs) that bind to HLA-C or CD94/NKG2A inhibitory receptors, and then bind HLA-E. Associations of certain KIR/HLA-C combinations with recurrent miscarriage, pre-eclampsia, and foetal growth restriction and the interactions between uNK cells, trophoblasts and vascular cells have led to the hypothesis that uNK cells may play a role in embryo implantation. OBJECTIVE AND RATIONALE: Our objective was to review the evolution of our understanding of uNK cells, their functions, and their increasingly relevant role in reproduction. SEARCH METHODS: Relevant literature through June 2020 was retrieved using Google Scholar and PubMed. Search terms comprised uNK cells, human pregnancy, reproductive failure, maternal KIR and HLA-C, HLA-E/G/F in EVT cells, angiogenic cytokines, CD56+ NK cells, spiral artery, oestrogen and progesterone receptors, KIR haplotype and paternal HLA-C2. OUTCOMES: This review provides key insights into the evolving conceptualization of uNK cells, from their not-so-promising beginnings to now, when they are considered allies in reproduction. We synthesized current knowledge about uNK cells, their involvement in reproduction and their main functions in placental vascular remodeling and trophoblast invasion. One of the issues that this review presents is the enormous complexity involved in studying the immune system in reproduction. The complexity in the immunology of the maternal-foetal interface lies in the great variety of participating molecules, the processes and interactions that occur at different levels (molecular, cellular, tissue, etc.) and the great diversity of genetic combinations that are translated into different types of responses. WIDER IMPLICATIONS: Insights into uNK cells could offer an important breakthrough for ART outcomes, since each patient could be assessed based on the combination of HLA and its receptors in their uNK cells, evaluating the critical interactions at the materno-foetal interface. However, owing to the technical challenges in studying uNK cells in vivo, there is still much knowledge to gain, particularly regarding their exact origin and functions. New studies using novel molecular and genetic approaches can facilitate the identification of mechanisms by which uNK cells interact with other cells at the materno-foetal interface, perhaps translating this knowledge into clinical applicability.

Parental human leukocyte antigen-C allotypes are predictive of live birth rate and risk of poor placentation in assisted reproductive treatment.

OBJECTIVE: To study the pregnancy, miscarriages, and live birth rates (LBRs) according to maternal killer cell immunoglobulin-like receptor (KIR) genes expressed by uterine natural killer cells and paternal or oocyte donor human leukocyte antigen-C (HLA-C) genes expressed by trophoblast cells in patients with recurrent reproductive failure. DESIGN: Prospective observational cohort study. SETTING: Private infertility center. PATIENT(S): Participants included 204 women with recurrent miscarriage or recurrent implantation failure. INTERVENTION(S): The KIR and HLA-C genotypes of all women and HLA-C of their partners, gamete donors, miscarriage tissue, and babies were analyzed. MAIN OUTCOME MEASURE(S): All clinical variables (pregnancy, miscarriage, and LBRs) were analyzed and categorized based on KIR, oocyte origin, and single embryo transfer (SET)/double embryo transfer (DET). RESULT(S): A higher miscarriage rate was observed after DETs in KIR AA mothers (47.8% egg donation and 37.5% in vitro fertilization [IVF]) compared with KIR AB (10.5% egg donation and 12.5% IVF) or KIR BB (6.7% egg donation and 0% IVF). A significantly decreased LBR was observed after DETs with oocyte donation in KIR AA patients (4.3%) compared with KIR AB (26.3%) or BB (46.7%). The LBR decreased significantly as the fetal HLA-C2 load increased in KIR AA women. CONCLUSION(S): Elective SET improves the reproductive outcomes compared with DET. An increased embryo HLA-C2 load has a negative impact on the LBR in KIR AA patients. The selection of HLA-C1 over HLA-C2 donors could have a positive impact on the LBR in KIR AA patients. CLINICAL TRIAL REGISTRATION NUMBER: NCT04052438.

Exploring undiagnosed celiac disease in women with recurrent reproductive failure: The gluten-free diet could improve reproductive outcomes.

PROBLEM: Which is the prevalence and seroprevalence of celiac disease (CD) in women with recurrent reproductive failure? METHOD OF STUDY: Retrospective study performed in a single infertility clinic from September 2016 to December 2017. A total of 690 women with unexplained history of recurrent miscarriage and/or recurrent implantation failure were consecutively recruited. IgA anti-transglutaminase 2 (TG2) antibody data were collected, as well as IgG anti-TG2 and IgA/IgG anti-deamidated gluten peptide (DGP) data in most cases, and IgG anti-gliadin antibodies occasionally. In selected women, HLA-DQ genotyping was requested. Biopsy was suggested to all women with positive serological results or belonging to CD risk groups. Reproductive outcomes were recorded from women with high suspicion of CD and a control group comprised of 49 women. RESULTS: Anti-TG2-positive women comprised 1% of the sample. An additional 4% was observed considering less-specific antibodies (31 women). Only 39% of sero-positive women accepted duodenal biopsy. HLA and biopsy data discarded CD in 14 sero-positive cases (37%), only one with anti-TG2 antibodies. CD was suggested in 10 sero-positive and three sero-negative women (1.9%). Compared with controls, the live birthrate of the studied women with probable CD was significantly decreased before gluten removal of the diet (P = .015), but significantly increased after that (P = .020). CONCLUSION: One percent CD prevalence should be expected after anti-TG2 serological screening. However, more sensitive approaches should be explored, especially considering the potential beneficial effect of the gluten-free diet on the reproductive outcomes of women with CD.

Use of granulocyte colony-stimulating factor in ART treatment does not increase the risk of adverse perinatal outcomes.

RESEARCH QUESTION: Granulocyte colony-stimulating factor (G-CSF) acts on reproductive function at different stages, but its effects on the early stages of embryo development are unknown. The aim of this study was to assess the effect of G-CSF administration during treatment with assisted reproductive technologies (ART) and early pregnancy on newborns. DESIGN: Retrospective study in women undergoing egg donation, with a study group including 33 live-born children from a pregnancy in which G-CSF was administered, and a control group of 3798 children in which this medication was not ordered during pregnancy. The analysis was of perinatal outcomes resulting from G-CSF treatment administered off-label compared with a control group. RESULTS: No significant differences were found in maternal age (40.9 ± 0.1 versus 38.9 ± 1.8, P = 0.055), body mass index (23.2 ± 0.2 versus 22.6 ± 1.5, P = 0.503), infant birthweight (2952 ± 200 versus 3145 ± 270 g, P = 0.184), gestational age (38 ± 1 versus 37 ± 1 weeks, P = 0.926) or length (50.2 ± 1.5 versus 48.7 ± 2.7 cm, P = 0.678) (between the control group and women treated with G-CSF, respectively). The prematurity rates of births before week 36 (10.0% versus 9.5%, P = 0.783) or week 32 (2.2% versus 0.0%, P = 0.585) were similar in the control and study groups, respectively. The incidence of low birthweight (<2500 g; 19.6% versus 11.8%, P = 0.570) or very low birthweight (1500 g; 2.5% versus 0.0%, P = 0.454) was not significantly different between non-treated and G-CSF-treated women, respectively. CONCLUSIONS: Administration of G-CSF at embryo transfer and during early pregnancy in recurrent miscarriage patients with KIR-HLA-C mismatch undergoing egg donation ART treatment does not convey a higher risk of perinatal complications.

Correction to: Imaging of Bronchial Pathology in Antibody Deficiency: Data from the European Chest CT Group.

In the original version of this article unfortunately two authors were missing: Dr. Jürgen Weidemann and Dr. Daniel Berthold. The correct list of authors is presented above.

Imaging of Bronchial Pathology in Antibody Deficiency: Data from the European Chest CT Group.

Studies of chest computed tomography (CT) in patients with primary antibody deficiency syndromes (ADS) suggest a broad range of bronchial pathology. However, there are as yet no multicentre studies to assess the variety of bronchial pathology in this patient group. One of the underlying reasons is the lack of a consensus methodology, a prerequisite to jointly document chest CT findings. We aimed to establish an international platform for the evaluation of bronchial pathology as assessed by chest CT and to describe the range of bronchial pathologies in patients with antibody deficiency. Ffteen immunodeficiency centres from 9 countries evaluated chest CT scans of patients with ADS using a predefined list of potential findings including an extent score for bronchiectasis. Data of 282 patients with ADS were collected. Patients with common variable immunodeficiency disorders (CVID) comprised the largest subgroup (232 patients, 82.3%). Eighty percent of CVID patients had radiological evidence of bronchial pathology including bronchiectasis in 61%, bronchial wall thickening in 44% and mucus plugging in 29%. Bronchiectasis was detected in 44% of CVID patients aged less than 20 years. Cough was a better predictor for bronchiectasis than spirometry values. Delay of diagnosis as well as duration of disease correlated positively with presence of bronchiectasis. The use of consensus diagnostic criteria and a pre-defined list of bronchial pathologies allows for comparison of chest CT data in multicentre studies. Our data suggest a high prevalence of bronchial pathology in CVID due to late diagnosis or duration of disease.

Pancreatic autoimmunity: An unknown etiology on patients with assisted reproductive techniques (ART)-recurrent reproductive failure.

Pancreatic Autoimmunity is defined as the presence of autoantibodies and more frequent need for insulin treatment. Affected women presenting recurrent implantation failure (RIF) or recurrent miscarriage (RM) are often misdiagnosed. The objective of thestudy was to describe clinical and metabolic profiles suggestive of Pancreatic Autoimmunity and therapeutic strategy in patients with RIF/RM. We analyzed retrospectively 735 patients, and have identified a subset (N = 20) with similar metabolic characteristics. At the same time, we included a control group (n = 39), with similar demographic characteristics and negative for pancreatic, thyroid or celiac disease autoimmunity. The patients identified with autoimmune metabolic problem (N = 20) had relatives with diabetes mellitus. At 120 minutes after Oral Glucose Tolerance Test (OGTT) low level of insulin secretion (<2 IU/ml) was found in 70% of patients. Glutamic acid decarboxylase 65 (GAD 65) antibodies, with or without other autoantibodies, were positive in80% of patients and anti-IA2 alone were positive I the rest. Since pregestational period, insulin administration was recommended for 10 patients, metformin for 4 patients and exclusively diet control in 5 of them. Significantly increased live bith rates (LBR) per cycle were observed after metabolic control (52%) compared with live birth rate (LBR) after cycles without control (7.5%) (p<0.0001). We noticed 2 cases of pre-eclampsia and 6 low-birth weights. Insulin administration was needed during the pregnancy in 68% of patients and after childbirth in 31.57% of them. In our control group, all of patients (n = 39) underwent ART (53.8% SET and 46.1% DET) with a 50% (SET) and 61.9% (DET) live birth rate (LBR) per cycle. Patients with RIF/RM, normal BMI, low insulin levels after OGTT could benefit from additional metabolic immune testing. A correct diagnosis and treatment could have a positive impact on their reproductive results and live birth rate.

Why natural killer cells are not enough: a further understanding of killer immunoglobulin-like receptor and human leukocyte antigen.

The immune system's role in recurrent reproductive failure is a controversial issue in assisted reproduction. Most studies into immune system implication in reproduction have focused on finding markers of peripheral blood and less on the uterine environment. Peripheral blood natural killer cells have become an "immune study core" for women with recurrent miscarriage or recurrent implantation failure, based on the mistaken notion that they cause reproductive failure by killing or "rejecting" the embryo. Maternal-fetal tolerance begins at the uterine level, so successful adaptation to the fetus occurs after a complicated process. Insufficient uterine lining invasion by an invading extravillous trophoblast is the primary defect in pregnancy disorders such as recurrent miscarriage. This process is regulated by the interaction between maternal killer immunoglobulin-like receptors (KIRs), expressed by uterine natural killer cells (uNK), and their ligand human leukocyte antigen (HLA) C, expressed by the extravillous trophoblast. Pregnancies are an increased risk of disorders in mothers with KIR AA when the fetus has paternal HLA-C2. A recent report has indicated that the expression of more than one paternal HLA-C by the extravillous trophoblast in assisted reproduction may affect placentation in mothers with KIR AA. This review provides insight into the immune system's role in assisted reproductive treatments. These insights can have an impact on the selection of single-embryo transfer and/or oocyte/sperm donor according to HLA-C in patients with recurrent implantation failure and recurrent miscarriage depending on their KIR haplotype.

Immunology and human reproduction.

PURPOSE OF REVIEW: The immune system's role in recurrent reproductive failure is a controversial issue in assisted reproduction. New insight about maternal tolerance in assisted reproduction has been reported and could explain some of the recurrent miscarriage and/or recurrent implantation failure related causes named until now as unknown. RECENT FINDINGS: Most of the previous studies about immune system implication in reproduction were focused on finding markers on peripheral blood. Maternal tolerance begins at the uterine level, so successful adaptation to the fetus happens after a complicated process. Insufficient invasion of the uterine lining by invading extravillous trophoblast is the primary defect in pregnancy disorders such as recurrent miscarriage, and this process is regulated by interaction between maternal killer immunoglobulin-like receptors (KIRs) expressed by the uterine natural killer cells and their ligand human leukocyte antigen (HLA)-C expressed by extravillous trophoblast. Pregnancies are an increased risk of disorders in mothers with KIR AA when the fetus has paternal HLA-C2. Recently, it has been reported that the expression of more than one paternal HLA-C by extravillous trophoblast in assisted reproduction may affect placentation in mothers with KIR AA. SUMMARY: The review provides insight about the immune tolerance process. These insights could have an impact on the selection of single embryo transfer and/or oocyte/sperm donor according to HLA-C in patients with recurrent miscarriage or recurrent implantation failure and a KIR AA haplotype.

Experience in IVIg therapy for selected women with recurrent reproductive failure and NK cell expansion.

PROBLEM: Recurrent reproductive failure (RRF) has been associated with expansion of circulating NK cells, key cells for maternal tolerance, decidual vasculogenesis and embryo growth. This study reports our experience in intravenous immunoglobulin (IVIg) therapy of a large cohort of women with RRF with expanded circulating NK and/or NKT-like cells (blood NKT cells are a heterogeneous subset of T cells that share properties of both T cells and NK cells). METHOD OF STUDY: Observational study of RRF women with NK or NKT-like expansion (>12% or 10% cutoff levels of total lymphocytes, respectively), treated with IVIg for the next gestation. RESULTS: By multivariant logistic regression analysis after adjusting for age, NK cells subsets and other therapies, IVIg significantly improved the live birth rate to 96.3% in women with recurrent miscarriage (RM) compared with 30.6% in case not receiving IVIg (P < 0.0001). In women with recurrent implantation failure (RIF), in comparison with women not receiving IVIg, treatment increased the pregnancy rate from 26.2 to 93.8% (P ≤ 0.0001) and the live birth rate from 17.9 to 80.0% in RIF (P ≤ 0.0001). CONCLUSIONS: Immunomodulation with IVIg in our selected group of RRF patients with immunologic alterations enhanced clinical pregnancy and live birth rates. Our results may facilitate the design of future clinical trials of IVIg in this pathology.