Decline in number of elevated blood CD3(+) CD56(+) NKT cells in response to intravenous immunoglobulin treatment correlates with successful pregnancy

Cataloging circulating CD3+CD56+ NKT-like cells through a series of stimulating (NKG2D and DNAM-1) and inhibitory (PD-1, TIGIT, and Tim-3) immune checkpoint receptors in women diagnosed with precancerous cervical lesions or invasive cervical carcinoma

Persistent human papillomavirus infection is associated with the development of premalignant lesions that can eventually lead to cervical cancer. In this study, we evaluated the expression of activating (NKG2D, DNAM-1) and inhibitory immune checkpoints receptors (PD-1, TIGIT, and Tim-3) in peripheral blood NKT-like (CD3+CD56+) lymphocytes from patients with cervical carcinoma (CC, n = 19), high-grade lesions (HG, n = 8), low-grade lesions (LG, n = 19) and healthy donors (HD, n = 17) using multiparametric flow cytometry. Dimensional data analysis showed four clusters within the CD3+CD56+ cells with different patterns of receptor expression. We observed upregulation of CD16 in CC and HG patients in one of the clusters. In another, TIGIT was upregulated, while DNAM-1 was downregulated. Throughout manual gating, we observed that NKT-like cells expressing activating receptors also co-express inhibitory receptors (PD-1 and TIGIT), which can affect the activation of these cells. A deeper characterization of the functional state of the cells may help to clarify their role in cervical cancer, as will the characterization of the NKT-like cells as cytotoxic CD8+ T cells or members of type I or type II NKT cells.

Natural Killer T-like Cells: Immunobiology and Role in Disease

CD56+ T cells are generally recognized as a distinct population of T cells and are categorized as NKT-like cells. Although our understanding of NKT-like cells is far from satisfactory, it has been shown that aging and a number of disease situations have impacted these cells. To construct an overview of what is currently known, we reviewed the literature on human NKT-like cells. NKT-like cells are highly differentiated T cells with "CD1d-independent" antigen recognition and MHC-unrestricted cell killing. The genesis of NKT-like cells is unclear; however, it is proposed that the acquisition of innate characteristics by T cells could represent a remodeling process leading to successful aging. Additionally, it has been shown that NKT-like cells may play a significant role in several pathological conditions, making it necessary to comprehend whether these cells might function as prognostic markers. The quantification and characterization of these cells might serve as a cutting-edge indicator of individual immune health. Additionally, exploring the mechanisms that can control their killing activity in different contexts may therefore result in innovative therapeutic alternatives in a wide range of disease settings.

The central role of natural killer cells in preeclampsia

Preeclampsia (PE) is a disease that is unique to pregnancy and affects multiple systems. It can lead to maternal and perinatal mortality. The precise etiology of PE is unclear. Patients with PE may have systemic or local immune abnormalities. A group of researchers has proposed that the immune communication between the fetus and mother is primarily moderated by natural killer (NK) cells as opposed to T cells, since NK cells are the most abundant immune cells in the uterus. This review examines the immunological roles of NK cells in the pathogenesis of PE. Our aim is to provide obstetricians with a comprehensive and updated research progress report on NK cells in PE patients. It has been reported that decidual NK (dNK) cells contribute to the process of uterine spiral artery remodeling and can modulate trophoblast invasion. Additionally, dNK cells can stimulate fetal growth and regulate delivery. It appears that the count or proportion of circulating NK cells is elevated in patients with or at risk for PE. Changes in the number or function of dNK cells may be the cause of PE. The Th1/Th2 equilibrium in PE has gradually shifted to an NK1/NK2 equilibrium based on cytokine production. An improper combination of killer cell immunoglobulin-like receptor (KIR) and human leukocyte antigen (HLA)-C may lead to insufficient activation of dNK cells, thereby causing PE. In the etiology of PE, NK cells appear to exert a central effect in both peripheral blood and the maternal-fetal interface. To maintain immune equilibrium both locally and systemically, it is necessary to take therapeutic measures directed at NK cells.

Functional prominence of natural killer cells and natural killer T cells in pregnancy and infertility: A comprehensive review and update

During pregnancy, complicated connections are formed between a mother and a fetus. In a successful pregnancy, the maternal-fetal interface is affected by dynamic changes, and the fetus is protected against the mother's immune system. Natural killer (NK) cells are one of the immune system cells in the female reproductive system that play an essential role in the physiology of pregnancy. NK cells not only exist in peripheral blood (PB) but also can exist in the decidua. Studies have suggested multiple roles for these cells, including decidualization, control of trophoblast growth and invasion, embryo acceptance and maintenance by the mother, and facilitation of placental development during pregnancy. Natural killer T (NKT) cells are another group of NK cells that play a crucial role in the maintenance of pregnancy and regulation of the immune system during pregnancy. Studies show that NK and NKT cells are not only effective in maintaining pregnancy but also can be involved in infertility-related diseases. This review focuses on NK and NKT cells biology and provides a detailed description of the functions of these cells in implantation, placentation, and immune tolerance during pregnancy and their role in pregnancy complications.

Live Birth Rate in Women with Recurrent Pregnancy Loss after In Vitro Fertilization with Concomitant Intravenous Immunoglobulin and Prednisone

Pregnancy loss after in vitro fertilization (IVF) is at least as common as after spontaneous conception. Recurrent pregnancy loss (RPL) may often have an immunological background, and it is therefore relevant to test immune-based interventions in these patients. The objective was to investigate the effect of immunotherapy with intravenous immunoglobulin (IvIg) and prednisone (PRS) as concomitant therapy to IVF in women with RPL after earlier IVF treatments. In a cohort study conducted at The Danish RPL Clinic, 41 women with three or more consecutive pregnancy losses after IVF underwent at least one further IVF cycle with concomitant immunotherapy from 2012 to 2017. The immunotherapy with IvIg and PRS was given before embryo transfer and repeatedly in the first trimester when pregnancy was achieved. Fourteen women (34.2%) achieved a live birth after the first embryo transfer with immunotherapy, and a total of 32/41 (78%) achieved a live birth after up to 4 embryo transfers. Baseline characteristics and the presence of autoantibodies were not significantly different among women achieving live birth or not. The observed 34% birth rate in women with RPL after IVF receiving immunotherapy appears higher than the expected 16-19% birth rate without immunotherapy and is similar to findings in a previous cohort from our clinic. Concomitant immunotherapy as described may be a promising intervention for women with RPL after IVF; however, the effect must be tested in a randomized controlled trial.

The Role of Type I and Type II NKT Cells in Materno-Fetal Immunity

NKT cells represent a small but significant immune cell population as being a part of and bridging innate and adaptive immunity. Their ability to exert strong immune responses via cytotoxicity and cytokine secretion makes them significant immune effectors. Since pregnancy requires unconventional maternal immunity with a tolerogenic phenotype, investigation of the possible role of NKT cells in materno-fetal immune tolerance mechanisms is of particular importance. This review aims to summarize and organize the findings of previous studies in this field. Data and information about NKT cells from mice and humans will be presented, focusing on NKT cells characteristics during normal pregnancy in the periphery and at the materno-fetal interface and their possible involvement in female reproductive failure and pregnancy complications with an immunological background.

Phenotypic characterization of NKT-like cells and evaluation of specifically related cytokines for the prediction of unexplained recurrent miscarriage

Problem

Immune system dysregulation is a major cause of unexplained recurrent miscarriage (URM). Women with URM need screening for their pregnancy microenvironment and immune regulators, to prevent spontaneous abortion.

Method of study

In this study we evaluated NKT-like cell subsets in peripheral venous blood of women with URM using flow cytometry. The expression levels of specifically related Th1 cytokines (IFN-γ and IL-2), Th2 cytokine (IL-4), and Th17 cytokines (IL-17), were measured using enzyme-linked immunosorbent assay.

Results

The percentage of CD16+CD56+NKT-like (Double Positive NKT-like; DPNKT-like) cell subset, and the levels of IL-2 and IFN-γ were significantly elevated in blood of non-pregnant and pregnant patients with URM compared with the healthy control groups, and these parameters were significantly increased after pregnancy in the same patients with URM. Based on the prevalence of the candidate immunological factors in patients with URM, the prognostic significance of the NKT-like cell subsets, IFN-γ and IL-2 profiles were evaluated as potential predictors of URM. A cut-off point of 2.55% for DPNKT-like cell subset in the blood and cut-off values of 39.5 and 20.5 pg/ml for the levels of IFN-γ and IL-2, respectively could be used for the prediction of the risk of spontaneous abortion. To the best of our knowledge, this is the first study that described the prognostic significance of the aforementioned immunological parameters before and after pregnancy, and highlighted the correlation of NKT-like cells and the candidate Th1 cytokines with pregnancy loss in women with URM.

Conclusions

DPNKT-like cells, IFN-γ and IL-2 patient profiles could be used as markers to predict the risk of miscarriage in patients with URM.

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Disturbance in the immune system's regulators is an essential factor for recurrent miscarriage.

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There is an urgent need for women who have suffered pregnancy loss to identify specific immune regulators that underline recurrent miscarriage, to prevent and control miscarriage.

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CD16+CD56+NKT-like cells, Interferon-γ and Interleukin-2 patient profile could be utilized as biomarkers to predict risk of miscarriage in women who have suffered spontaneous miscarriage.

NK cells that differ in expression of NKp46 might play different roles in endometrium

NKp46 is a natural cytotoxicity receptor expressed by NK cells and its expression is decreased in reproductive failure patients. NKp46 can be subdivided into NKp46^dim and NKp46^bright according to different fluorescence staining intensities. We investigated the role of the NKp46 receptor in determining the reproductive outcomes. Uterine endometrium was collected from 34 women with reproductive failure and divided into the pregnant and failed groups based on the results of a pregnancy reaction test during a 1-year follow-up period. NKp46 receptor and other activating or inhibitory receptors expressed on NK cells as well as intracellular cytokine production by NK cells were analyzed by multicolor flow cytometry. In the failed group, the percentage of NKp46^dim NK cells (P < 0.05) was significantly higher and percentages of NKp46^bright NK cells (P < 0.01) and CD16^-/CD56^bright NK cells (P < 0.05) were significantly lower than those in the pregnant group. NKp46^dim NK cells were significantly and positively correlated with CD16⁺/NKp46^dim NK cells; NKp46^bright NK cells were significantly and positively correlated with CD16^-/NKp46^bright NK cells. CD16⁺/NKp46^dim NK cells were significantly and positively correlated with IFN-γ- and/or TNF-α-producing NK cells; CD16^-/NKp46^bright NK cells were significantly and positively correlated with TGF-β1-producing NK cells. We suggest that the NKp46 receptor plays different roles in reproduction based on the different fluorescence intensities associated with NK cells, i.e. NKp46^dim NK cells are involved in killing cells, whereas NKp46^bright NK cells are involved in cytokine production, indicating that NKp46 could be a predictive marker to see a tolerate condition for embryos.

A phase I/II clinical trial on the efficacy and safety of NKT cells combined with gefitinib for advanced EGFR-mutated non-small-cell lung cancer

Background

Epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs), such as gefitinib, have achieved good efficacy in EGFR mutation-positive non-small-cell lung cancer (NSCLC) patients, but eventual drug resistance is inevitable. Thus, new TKI-based combination therapies should be urgently explored to extend the overall survival time of these patients. CD8 + CD56+ natural killer T (NKT) cells are a natural and unique subset of lymphocytes in humans that present characteristics of T and NK cells and exert cytotoxicity on tumour cells in a granzyme B-dependent manner. The aim of this trial was to explore the efficacy and safety of CD8 + CD56+ NKT cell immunotherapy combined with gefitinib in patients with advanced EGFR-mutated NSCLC.

Methods

The study was designed as a prospective, randomized, controlled, open-label, phase I/II trial that includes 30 patients with EGFR mutation-positive stage III/IV NSCLC. All patients will be randomized in blocks at a 1:1 ratio and treated with gefitinib 250 mg/day monotherapy or combination therapy with allogeneic CD8 + CD56+ NKT cell infusions twice per month for 12 cycles or until disease progression occurs. The effectiveness of this treatment will be evaluated based on by progression-free survival (PFS), the time to progression (TTP), overall response rate (ORR), disease control rate (DCR) and overall survival (OS). The safety of the trail is being assessed based on adverse events (AEs). Recruitment and data collection, which started in December 2017, are ongoing.

Discussion

Although immunotherapy, including programmed death-1/programmed death-1 ligand (PD-1/PD-L1) immunotherapy, has been used for NSCLC treatment with or without EGFR-TKIs, its clear efficacy still has not been shown. Assessing the safety and therapeutic potential of allogeneic CD8 + CD56+ NKT killer cells in combination with EGFR-TKIs in NSCLC will be of great interest.

Trial registration

This trial (Phase I/II Trails of NKT Cell in Combination With Gefitinib For Non Small Cell Lung Cancer) was registered on 21 November 2017 with www.chictr.org.cn, ChiCTR-IIR-17013471.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-08590-1.

The Effects of LIT and MLR-Bf on Immune Biomarkers and Pregnancy Outcomes in Women With Previous Early Recurrent Miscarriage: A Retrospective Study

Background: Immunological failure during pregnancy is considered one of the etiologies of recurrent miscarriage (RM). The decreased production of mixed lymphocyte reaction-blocking factors (MLR-Bf) may play a major role in this condition. Lymphocyte immunotherapy (LIT), which induces the production of MLR-Bf, has been used in treating RM patients since 1984. However, the effectiveness of LIT is currently being heatedly debated. In addition to that, possible changes to the maternal immune system upon induced MLR-Bf production by LIT remains unclear. Objectives: To explore the possible impacts that MLR-Bf may have on the expression of immune biomarkers and pregnancy outcomes, and deduce whether the prevention of miscarriages is possible with LIT or MLR-Bf in RM patients. Materials and Methods: Women with previous early RM (eRM) were enrolled in this retrospective study after they got pregnant again. LIT was implemented before pregnancy and during the first trimester. MLR-Bf and immune biomarkers were checked as the clinical routine. Patients were followed up until 12 gestational weeks. Levels of immune biomarkers and successful pregnancy rates were compared between MLR-Bf^- group and MLR-Bf⁺ group stratified by LIT. Independent associations between LIT, or MLR-Bf, and miscarriage were estimated. All data management and analysis were conducted using SPSS 20.0. Results: A total of 1,038 patients, 497 MLR-Bf^- (49 cases accepted LIT), and 541 MLR-Bf⁺(463 cases induced by LIT) were included in the study. Percentage of lymphocytes, the ratio of CD4+ T cells/lymphocytes, and levels of some rheumatoid biomarkers (anti-U1-nRNP, anti-SAA-52kd, and anti-CENOP B) were statistically higher in MLR-Bf⁺ group than in MLR-Bf^- group among women without LIT. With LIT treatment the successful pregnancy rate was statistically higher in MLR-Bf⁺ group than in MLR-Bf^- group (66.7% vs. 51.0%, P = 0.028) among women with LIT. Meanwhile, LIT was estimated to have an independent negative association with miscarriage. Conclusion: Upon LIT treament levels of immune biomarkers were different in women with and without MLR-Bf when stratified by whether they received LIT. Not MLR-Bf, but LIT, has an independent protective effect on miscarriage.

Co-expression of NKp46 with activating or inhibitory receptors on, and cytokine production by, uterine endometrial NK cells in recurrent pregnancy loss

NKp46 (CD335) is one of the activating receptors expressed on NK cells and its expression is decreased in patients with reproductive failure. However, the reasons remain unknown. In this study, we aimed to clarify the significance of decreased NKp46 expression in reproductive failure. Uterine endometrial samples collected from 39 patients with recurrent pregnancy loss (RPL) were assigned to high- or low-risk groups based on an 18 % ratio of CD16⁺/CD56^dim NK cells in uterine endometrial NK (uNK) cells. We analyzed the expression of NKp46 and other activating or inhibitory receptors on, and intracellular cytokine production by NK cells using multicolor flow cytometry. The numbers of NKp46⁺/CD16^- NK, NKp46⁺/NKG2C^- NK, IL-4⁺/CD56⁺ NK, and IL-10⁺/CD56⁺ NK cells were significantly decreased, whereas that TNF-α⁺/CD56⁺ NK cells was significantly increased in the high-risk group, when compared with the low-risk group (P < 0.05 for all). The ratios of TNF-α/IL-4, IFN-γ/IL4, TNF-α/IL-10, and IFN-γ/IL10 cytokine production in uNK cells were significantly increased in the high-risk when compared with the low-risk group (P < 0.05, for all). It is suggested that low expression of activating receptors on NKp46 uNK cells is more prevalent in high-risk women.

Is there a Role of Intravenous Immunoglobulin in Immunologic Recurrent Pregnancy Loss?

Recurrent pregnancy loss (RPL) commonly refers to three or more miscarriages that occur before 20 weeks of pregnancy. The immunological cause of RPL could be either an auto- or alloimmune-related event or both. Because of the discovery of immunological abnormalities in RPL patients in clinical practice, several immunomodulatory therapies were introduced to maintain the immune balance at the maternal-fetal interface. Intravenous immunoglobulin (IVIg) is one of the immunomodulators. In recent years, several studies have analyzed the therapeutic effect of IVIg on RPL patients with antiphospholipid syndrome (APS) or unexplained RPL. However, their results are controversial. IVIg can be used in RPL patients with APS who have previously failed in other treatments. It is recommended that IVIg infusion could be considered used before conception in RPL patients who have cellular immune abnormalities such as increased natural killer (NK) cell counts, NK cell cytotoxicity, or increased T helper (Th)1/Th2 ratio, depending on the cut-off values of each hospital. The aim of this review was to summarize the mechanisms, efficacy, pharmacokinetics, and side effects associated with passive immunization using IVIg in immunologic RPL, according to the literature published in recent years. We hope that more obstetricians will be able to understand the timing and indication of IVIg properly in immunologic RPL patients and effectively enhance pregnancy outcomes for mothers and neonates.

Dysfunction of Tregs contributes to FGR pathogenesis via regulating Smads signalling pathway

Fetal growth restriction (FGR) is ranked number two of most common complication of abnormal pregnancy worldwide. The pathogenesis of FGR is complicated due to multiple aetiologies and the exact mechanism for FGR development is currently unknown. T regulatory cells (Tregs) are proven to play central roles in the maintenance of normal pregnancy. Peripheral blood samples of 102 pregnant human were collected analysed using flow cytometry to identify Tregs. We found that reduced Tregs and down-regulation of Foxp3 were observed in peripheral blood of FGR patients. In FGR mouse model, we have found that Tregs were not only reduced in spleen but also in placenta. In vitro, Foxp3 and its transcription regulatory signalling molecules, including P-Smad2, P-Smad3 and Smad4, were diminished as well. Inhibition on Foxp3 expression was partially reversed by overexpression of Smad2 and Smad4. In FGR patients, Western blot results revealed that Foxp3, P-Smad2, P-Smad3 and Smad4 expression was inhibited in placenta. Our preliminary result suggests that maternal-foetal immune tolerance mediated by Tregs plays an essential role in the development of FGR. The inhibited expression of Foxp3 and down-regulated Smad2/Smad3/Smad4 signalling pathway were involved in the FGR pathogenesis. Targeting maternal-foetal immune tolerance through Tregs might represent a novel therapeutic option for FGR.

Treatment with intravenous immunoglobulin in patients with recurrent pregnancy loss: An update

Intravenous immunoglobulin (IVIg) has a documented clinical effect in many autoimmune diseases and has so far been tested in >10 randomised controlled trials (RCTs) in women with recurrent pregnancy loss (RPL). The results of the RCTs have, however, been very divergent. In meta-analyses of all trials, no significant impact on live birth rate has been reported. In contrast, in sensitivity analyses, IVIg significantly increased live birth rates when initiated prior to conception and it had a borderline significant therapeutic effect in women with secondary RPL. Higher dosages of IVIg and serological signs of autoimmunity in the treated patients tended to increase the success rate after treatment. A follow-up study of patients from our recent RCT also supports a significant therapeutic effect in patients who had received IVIg before conception. The lessons learned from the published trials and meta-analyses should be incorporated in the design of future RCTs of IVIg in the treatment of RPL.

Characterization of circulating T-, NK-, and NKT cell subsets in patients with colorectal cancer: the peripheral blood immune cell profile

Objective

As the development and progression of colorectal cancer (CRC) are known to be affected by the immune system, cell subsets such as T cells, natural killer (NK) cells, and natural killer T (NKT) cells are considered interesting targets for immunotherapy and clinical biomarker research. Until now, the role of systemic immune profiles in tumor progression remains unclear. In this study, we aimed to characterize the immunophenotype of circulating T cells, NK cells, and NKT-like cells in patients with CRC, and to subsequently correlate these immunophenotypes to clinical follow-up data.

Methods

Using multiparameter flow cytometry, the subset distribution and immunophenotype of T cells (CD3⁺CD56⁻), CD56^dim NK cells (CD3⁻CD56^dim), CD56^bright NK cells (CD3⁻CD56^bright), and NKT-like (CD3⁺CD56⁺) cells were investigated in peripheral blood mononuclear cell (PBMC) samples from 71 CRC patients and 19 healthy donors.

Results

CRC patients showed profound differences in immune cell subset distribution and their immunophenotype compared to healthy donors, as characterized by increased percentage of regulatory T cells, and reduced expression level of the natural cytotoxicity receptors NKp44 and NKp46 on both CD56^dim NK cells and NKT-like cells. Finally, we showed in a multivariate analysis that above-median percentage of CD16⁺ NKT-like cells was independently associated with shorter disease-free survival in CRC patients.

Conclusion

The altered phenotype of circulating immune cell subsets in CRC and its association with clinical outcome highlight the potential use of PBMC subsets as prognostic biomarkers in CRC, thereby contributing to better insight into the role of systemic immune profiles in tumor progression.

Electronic supplementary material

The online version of this article (10.1007/s00262-019-02343-7) contains supplementary material, which is available to authorized users.

Modulatory effect of intravenous immunoglobulin on Th17/Treg cell balance in women with unexplained recurrent spontaneous abortion

Recurrent spontaneous abortion (RSA) is a growing problem worldwide. In a majority of cases, the cause remains unknown but there is increasing evidence that immunologic factors play an important role. Intravenous immunoglobulin (IVIg) therapy has been proposed to have immune modulatory effects and therefore been applicable for the treatment of patients with RSA. Although its efficacy is still controversial, several recent studies suggest that IVIg treatment may improve pregnancy outcomes. CD4⁺ T cells and their related cytokines play an important role in maternal-fetal immune regulation, and an imbalance of Th17/Treg cell ratio has been proposed as a cause for RSA. We review the scientific evidence supporting a modulatory effect of IVIg on Th17/Treg cell balance and discuss the potential mechanisms how IVIg might enhance Treg cells function. We propose that correction of Th17/Treg cell dysregulation could be one of the mechanisms that can explain the positive therapeutic effects of IVIg therapy. Consequently, selecting patients with abnormal Th17/Treg cell ratios could increase the success of IVIg therapy.

Diminished Frequency of Menstrual and Peripheral Blood NKT-Like Cells in Patients With Unexplained Recurrent Spontaneous Abortion and Infertile Women

Systemic monitoring of immune system may not precisely outline the local immune status in the uterus. This survey is a continuation of our previous studies on potential usefulness of menstrual blood (MB) immunophenotyping as a tool for investigation of immunological disturbances in pregnancy-related disorders. Peripheral blood (PB) and MB from healthy fertile (n = 15), unexplained recurrent spontaneous abortion (URSA; n = 15), and unexplained infertile women (n = 8) were collected simultaneously in the second day of their menstrual cycle and frequency of natural killer T (NKT)-like cell subpopulations were assessed by flow cytometry. Menstrual blood of all experimental groups contained higher percentage of TCRαβ⁺, CD45RO⁺, and CD16^- NKT-like cells compared to corresponding PB. Frequency of MB NKT-like cells in unexplained infertile participants was lower than fertile and URSA groups. Compared to normal participants, patients with URSA had lower frequency of PB TCRαβ⁺ and higher CD16⁺, while in infertile woman frequencies of PB CD45RO⁺, CD45RO^-, CD16^-, IL17⁺, and MB CD45RO⁺ NKT-like cells were lower. Although, PB and MB seemingly have the same histological nature, our results showed that MB contained different composition of NKT-like subsets with different cytokine profiles and could be viewed as one potential biological sample for evaluation of patients with infertility and URSA.

The Role of Natural Killer T Cells in Cancer-A Phenotypical and Functional Approach

Natural killer T (NKT) cells are a subset of CD1d-restricted T cells at the interface between the innate and adaptive immune system. NKT cells can be subdivided into functional subsets that respond rapidly to a wide variety of glycolipids and stress-related proteins using T- or natural killer (NK) cell-like effector mechanisms. Because of their major modulating effects on immune responses via secretion of cytokines, NKT cells are also considered important players in tumor immunosurveillance. During early tumor development, T helper (T_H)1-like NKT cell subsets have the potential to rapidly stimulate tumor-specific T cells and effector NK cells that can eliminate tumor cells. In case of tumor progression, NKT cells may become overstimulated and anergic leading to deletion of a part of the NKT cell population in patients via activation-induced cell death. In addition, the remaining NKT cells become hyporesponsive, or switch to immunosuppressive T_H2-/T regulatory-like NKT cell subsets, thereby facilitating tumor progression and immune escape. In this review, we discuss this important role of NKT cells in tumor development and we conclude that there should be three important focuses of future research in cancer patients in relation with NKT cells: (1) expansion of the NKT cell population, (2) prevention and breaking of NKT cell anergy, and (3) skewing of NKT cells toward T_H1-like subsets with antitumor activity.

Immune modulation of i.v. immunoglobulin in women with reproductive failure

Background

The mechanism of maternal immune tolerance of the semi‐allogenic fetus has been explored extensively. The immune reaction to defend from invasion by pathogenic microorganisms should be maintained during pregnancy. An imbalance between the immune tolerance to the fetus and immune activation to the pathogenic organisms is associated with poor pregnancy outcomes. This emphasizes that the immune mechanism of successful reproduction is not just immune suppression, but adequate immune modulation.

Methods

In this review, the action of i.v. immunoglobulin G (IVIg) on the immune system and its efficacy in reproductive failure (RF) was summarized. Also suggested is the indication of IVIg therapy for women with RF.

Main findings (Results)

Based on the mechanism of the immune regulation of IVIg and following confirmation of the immune modulation effects of it in various aberrant immune parameters in patients with RF, it is obvious that IVIg is effective in recurrent pregnancy losses and repeated implantation failures with immunologic disturbances.

Conclusion

The authors recommend IVIg therapy in patients with RF with aberrant cellular immunologic parameters, including a high natural killer cell proportion and its cytotoxicity or elevated T helper 1 to T helper 2 ratio, based on each clinic's cut‐off values. Further clinical studies about the safety of IVIg in the fetus and its efficacy in other immunologic abnormalities of RF are needed.

Intravenous immunoglobulin G in women with reproductive failure: The Korean Society for Reproductive Immunology practice guidelines

The task force of the Korean Society for Reproductive Immunology recommends intravenous immunoglobulin G treatment in women with reproductive failure, including recurrent pregnancy loss and/or repeated implantation failure, who show cellular immune factors such as abnormal natural killer cell levels, natural killer cell cytotoxicity, and/or type 1 T helper immunity.

Immune regulatory network in successful pregnancy and reproductive failures

Maternal immune system must tolerate semiallogenic fetus to establish and maintain a successful pregnancy. Despite the existence of several strategies of trophoblast to avoid recognition by maternal leukocytes, maternal immune system may react against paternal alloantigenes. Leukocytes are important components in decidua. Not only T helper (Th)1/Th2 balance, but also regulatory T (Treg) cells play an important role in pregnancy. Although the frequency of Tregs is elevated during normal pregnancies, their frequency and function are reduced in reproductive defects such as recurrent miscarriage and preeclampsia. Tregs are not the sole population of suppressive cells in the decidua. It has recently been shown that regulatory B10 (Breg) cells participate in pregnancy through secretion of IL-10 cytokine. Myeloid derived suppressor cells (MDSCs) are immature developing precursors of innate myeloid cells that are increased in pregnant women, implying their possible function in pregnancy. Natural killer T (NKT) cells are also detected in mouse and human decidua. They can also affect the fetomaternal tolerance. In this review, we will discuss on the role of different immune regulatory cells including Treg, γd T cell, Breg, MDSC, and NKT cells in pregnancy outcome.

The effect of intravenous immunoglobulin passive immunotherapy on unexplained recurrent spontaneous abortion: a meta-analysis

The aim of this study was to investigate the effect of passive immunotherapy using intravenous immunoglobulin (IVIG) on unexplained recurrent spontaneous abortion (RSA). Live birth rates were analysed and binary data were calculated using risk ratio and 95% confidence interval. Meta-analysis of 11 studies showed that the difference in the live birth rate between the IVIG treatment and placebo groups was on the margin of significance (RR = 1.25, 95% CI 1.00 to 1.56, P = 0.05). Both cumulative and trial sequential meta-analyses indicated potential beneficial effect of IVIG but the evidence was inconclusive. Subgroup analysis showed that the live birth rate in primary (RR = 0.88, 95% CI 0.71 to 1.07) and secondary (RR = 1.26, 95% CI 0.99 to 1.61) RSA patients was not significantly different between the IVIG and placebo groups. Live birth rate was significantly different when IVIG was administered before conception (RR = 1.67, 95% CI 1.30 to 2.14, P < 0.0001) but not after implantation (RR = 1.10, 95% CI 0.93 to 1.29). Evidence is insufficient to support the beneficial effects of IVIG on an unexplained RSA. Further high quality studies are needed to elucidate the effectiveness of IVIG.

Immunogenetic contributions to recurrent pregnancy loss

While sporadic pregnancy loss is common, occurring in 15 % of pregnancies, recurrent pregnancy loss (RPL) impacts approximately 5 % of couples. Though multiple causes are known (including structural, hormonal, infectious, autoimmune, and thrombophilic causes), after evaluation, roughly half of all cases remain unexplained. The idiopathic RPL cases pose a challenging therapeutic dilemma in addition to incurring much physical and emotional morbidity. Immunogenetic causes have been postulated to contribute to these cases of RPL. Natural Killer cell, T cell expression pattern changes in the endometrium have both been shown in patients with RPL. Human leukocyte antigen (HLA) and cytokine allelic variations have also been studied as etiologies for RPL. Some of the results have been promising, however the studies are small and have not yet put forth outcomes that would change our current diagnosis and management of RPL. Larger database studies are needed with stricter control criteria before reasonable conclusions can be drawn.

Effects of polyvalent immunoglobulins in patients with recurrent pregnancy loss and antibodies to the choriocarcinoma cell line JEG-3

OBJECTIVE

The benefit of polyvalent immunoglobulins (IVIG) for patients with recurrent pregnancy loss (RPL) is controversially discussed. Anti-trophoblast antibodies as an expression of immune pathology have been associated with RPL. We investigated whether the antibody activity against the choriocarcinoma cell line JEG-3 in RPL patients is influenced in vitro by IVIG.

STUDY DESIGN

Sera of 110 unexplained RPL patients with positive anti-JEG-3 antibodies were coincubated with IVIG in different concentrations (10mg/ml, 20mg/ml, 40mg/ml). Coincubation with human albumin in identical concentrations served as control. Anti-JEG-3 reactivity was measured by using flow cytometry in comparisons with two in-house standards antibody probes of low and high reactivity as described before. Anti-JEG-3 reactivity above the 95% confidence interval of controls was defined as positive.

RESULTS

Incubating RPL sera with 10mg/ml IVIG significantly decreased anti-JEG-3 activity (p<0.001). Increasing IVIG concentration to 40mg/ml resulted in a slightly additionally reduction (p=0.42). In contrast, coincubation with albumin in identically concentrations did not affect anti-JEG-3 activity (p>0.40).

CONCLUSION

Coincubation with IVIG in vitro leads to a significant suppression of anti-JEG-3 activity in the sera of RPL patients.

Homing receptor expression is deviated on CD56+ blood lymphocytes during pregnancy in Type 1 diabetic women

Type 1 Diabetes Mellitus (T1DM) is characterized by an augmented pro-inflammatory immune state. This contributes to the increased risk for gestational complications observed in T1DM mothers. In normal pregnancies, critical immunological changes occur, including the massive recruitment of lymphocytes, particularly CD56^bright NK cells, into early decidua basalis and a 2^nd trimester shift towards Type 2 immunity. Decidual CD56^bright NK cells arise at least partly from circulating progenitors expressing adhesion molecules SELL and ITGA4 and the chemokine receptors CXCR3 and CXCR4. In vitro studies show that T1DM reduces interactions between blood CD56⁺ NK cells and decidual endothelial cells by reducing SELL and ITGA4-based interactions. To address the mechanisms by which specific lymphocyte subsets may be recruited from the circulation during pregnancy and whether these mechanisms are altered in T1DM, flow cytometry was used to examine eight peripheral blood lymphocyte subsets (Type 1 (IL18R1⁺) and Type 2 (IL1RL1⁺) CD56^bright NK, CD56^dim NK, NKT and T cells) from control and T1DM women. Blood was collected serially over pregnancy and postpartum, and lymphocytes were compared for expression of homing receptors SELL, ITGA4, CXCR3, and CXCR4. The decline of Type 1/Type 2 immune cells in normal pregnancy was driven by an increase in Type 2 cells that did not occur in T1DM. CD56^bright NK cells from control women had the highest expression of all four receptors with greatest expression in 2^nd trimester. At this time, these receptors were expressed at very low levels by CD56^bright NK cells from TIDM patients. Type 1/Type 2 NKT cell ratios were not influenced by either pregnancy or TIDM. Our results suggest that T1DM alters immunological balances during pregnancy with its greatest impact on CD56^bright NK cells. This implicates CD56^bright NK cells in diabetic pregnancy complications.

Role of Natural Killer Cells in Intravenous Immunoglobulin-Induced Graft-versus-Host Disease Inhibition in NOD/LtSz-scidIL2rg(-/-) (NSG) Mice

Although clinical studies have yet to demonstrate clearly the use of intravenous immunoglobulin (IVIG) for prevention of graft-versus-host disease (GVHD), their effective use in a xenogeneic mouse model has been demonstrated. We aimed to determine the mechanism of action by which IVIG contributes to GVHD prevention in a xenogeneic mouse model. NOD/LtSz-scidIL2rg(-/-) (NSG) mice were used for our xenogeneic mouse model of GVHD. Sublethally irradiated NSG mice were injected with human peripheral blood mononuclear cells (huPBMCs) and treated weekly with PBS or 50 mg IVIG. Incidence of GVHD and survival were noted, along with analysis of cell subsets proliferation in the peripheral blood. Weekly IVIG treatment resulted in a robust and consistent proliferation of human natural killer cells that were activated, as demonstrated by their cytotoxicity against K562 target cells. IVIG treatment did not inhibit GVHD when huPBMCs were depleted in natural killer (NK) cells, strongly suggesting that this NK cell expansion was required for the IVIG-mediated prevention of GVHD in our mouse model. Moreover, inhibition of T cell activation by either cyclosporine A (CsA) or monoclonal antihuman CD3 antibodies abolished the IVIG-induced NK cell expansion. In conclusion, IVIG treatment induces NK cell proliferation, which is essential for IVIG-mediated protection of GVHD in our mouse model. Furthermore, activated T cells are mandatory for effective IVIG-induced NK cell proliferation. These results shed light on a new mechanism of action of IVIG and could explain why the efficacy of IVIG in preventing GVHD in a clinical setting, where patients receive CsA, has never been undoubtedly demonstrated.

Sphingolipid pathway regulates innate immune responses at the fetomaternal interface during pregnancy

For a successful pregnancy, the mother's immune system has to tolerate the semiallogeneic fetus. A deleterious immune attack is avoided by orchestration of cellular, hormonal, and enzymatic factors. However, the precise mechanisms underlying fetomaternal tolerance are not yet completely understood. In this study, we demonstrate that sphingolipid metabolism constitutes a novel signaling pathway that is indispensable for fetomaternal tolerance by regulating innate immune responses at the fetomaternal interface. Perturbation of the sphingolipid pathway by disruption of the sphingosine kinase gene (Sphk) during pregnancy caused unusually high expression of neutrophil chemoattractants, CXCL1 and CXCL2, in the decidua, leading to a massive infiltration of neutrophils into the fetomaternal interface with enhanced oxidative damage, resulting in early fetal death. Sphk-deficient mice also exhibited neutrophilia in the peripheral blood, enhanced generation of granulocytes in the bone marrow, and a decrease in the number of decidual natural killer cells. The blockage of neutrophil influx protected Sphk-deficient mice against pregnancy loss. Notably, a similar result was obtained in human decidual cells, in which Sphk deficiency dramatically increased the secretion of CXCL1 and IL-8. In conclusion, our findings suggest that the sphingolipid metabolic pathway plays a critical role in fetomaternal tolerance by regulating innate immunity at the fetomaternal interface both in mice and humans, and it could provide novel insight into the development of therapeutic strategies to treat idiopathic pregnancy loss in humans.

Immunomodulatory treatment with intravenous immunoglobulin and prednisone in patients with recurrent miscarriage and implantation failure after in vitro fertilization/intracytoplasmic sperm injection

OBJECTIVE

To assess outcome in terms of live-birth rate after fresh or frozen IVF/intracytoplasmic sperm injection assisted reproductive technology (ART) cycles where immunomodulation was given to patients with recurrent pregnancy loss after prior ART treatments.

DESIGN

Retrospective cohort study.

SETTING

Tertiary care university hospital.

PATIENT(S)

Fifty-two patients with a history of at least three consecutive pregnancy losses after ART who underwent at least one further ART cycle with concurrent immunomodulation in 2003-2012.

INTERVENTION(S)

Immunomodulation with IV immunoglobulin and prednisone starting from before ET and continuing in the first trimester if pregnancy was established.

MAIN OUTCOME MEASURE(S)

Live-birth rate per ET and cumulative live-birth rate after up to five ETs.

RESULT(S)

Nineteen patients (36.5%) achieved a live birth after the first ET with immunomodulation, and a total of 32 patients achieved a live birth in the study period, resulting in a cumulative live-birth rate of 61.5%. There was no significant difference in baseline and immunological parameters between the patients achieving a live birth or not. The live-birth rate after the first immunomodulated ART cycle in our patients is higher than that reported in a previous study.

CONCLUSION(S)

Immunomodulation with a combination of IV immunoglobulin and prednisone is a promising treatment for recurrent pregnancy loss after ART, but randomized placebo-controlled trials are needed.

The use and misuse of animal analog models of human pregnancy disorders

It has been suggested that the differences between placentation in humans and rodents, such as mice, are sufficient to render human pregnancy unique and to justify ignoring data generated using mice. Detailed examination of the placenta-decidua interaction and decidual NK cell composition in humans, and mice, show that the principles are the same. Indeed, the rat placenta is useful in showing an intermediary arrangement between humans and mice. This is consistent with the thesis of Darwin that structures of older species evolve with development of new species to provide a survival advantage. Molecular details may differ between species, but also between individuals given gene polymorphisms. Human data on interaction of HLA-C2 with NK cell KIR receptors has been used to suggest that human pregnancy problems such as recurrent miscarriage, fetal growth retardation, and pre-eclampsia are due to lack of activation of true uterine NK cell (TuNK) functions that promote trophoblast cell growth and invasion which prevents such problems. But when TuNKs bear certain KIR phenotypes, pathology results. It is shown that such mechanisms could only be pertinent in less than one-third of recurrent miscarriage patients. Activated blood-type NK cells that enter the uterus (BuNKs) remain the major effector of pregnancy loss in humans, and this is consistent with data from the mouse. The importance of activated BuNKs in pre-eclampsia and fetal growth retardation merits further investigation as pre-eclampsia and fetal growth restriction are also manifest in the CBAxDBA/2 mouse model where activated NK cells are the initiator of abortions.

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.

Natural killer cells in female infertility and recurrent miscarriage: a systematic review and meta-analysis

INTRODUCTION Embryo implantation is a complex process involving maternal hormonal changes, immune responses and maturational events in the embryo. A pregnancy could fail when these events are not synchronized. It is speculated that in women, an elevation of natural killer (NK) cells may have an effect on reproductive performance, and NK cell levels in blood are currently being used as a diagnostic test to guide the initiation of therapies in patients with infertility. METHODS We conducted a systematic review to evaluate the (i) levels of NK cells in blood and endometrium in infertile versus fertile women, (ii) association between NK cells and IVF outcome, (iii) levels of NK cells in blood and endometrium in women with recurrent miscarriage (RM) versus controls. The following electronic databases were searched: Medline, EMBASE, Cochrane Library, Web of Science and National Research Register. RESULTS A total of 22 studies were included. Meta-analysis of studies that evaluated peripheral and uterine NK (uNK) cell percentages in infertile versus fertile women showed no significant difference between the two groups [standardized mean difference (SMD) -0.33; 95% confidence intervals (CI) -1.06, 0.4; P = 0.37; SMD -1.82; 95% CI -4.80, 1.17; P = 0.23 respectively]. Pooling of studies that reported peripheral NK cells as numbers showed significantly higher NK cell numbers in infertile women compared with fertile controls (SMD 3.16; 95% CI 1.07, 5.24; P = 0.003). Meta-analysis of studies that evaluated the role of NK cells in IVF outcome showed no significant difference in live birth rates in women with elevated NK cells or NK cell activity compared with women without elevated peripheral NK cells or NK cell activity (NK activity assessed using a cytotoxicity assay) (relative risk 0.57; 95% CI 0.06, 5.22; P = 0.62). Meta-analysis of studies that evaluated peripheral NK cell percentages in women with RM versus controls showed significantly higher NK cell percentages in women with RM (SMD 1.36; 95% CI 0.04, 2.69; P = 0.04). Meta-analysis of studies that evaluated peripheral NK cell numbers showed significantly higher NK cell numbers in women with RM compared with controls (SMD 0.81; 95% CI 0.47, 1.16; P < 0.00001). Meta-analysis of studies that evaluated uNK cells showed no significant difference in women with RM compared with controls (SMD 0.40; 95% CI -1.24, 2.04; P = 0.63). CONCLUSIONS Further research is needed before NK cell assessment can be recommended as a diagnostic tool in the context of female infertility or RM. There is no clear explanation as to why the results differ when data for NK cells are expressed as numbers or a percentage. On the basis of current evidence, NK cell analysis and immune therapy should be offered only in the context of clinical research.

Determination of clinical cellular immune markers in women with recurrent pregnancy loss

PROBLEM

Dysregulated natural killer (NK) immunity and T-cell immunity are associated with recurrent pregnancy loss (RPL). We aim to define clinically relevant NK and T-cell parameters for RPL and determine their cutoff values.

METHODS OF STUDY

Ninety-five women with RPL (>3) including 42 idiopathic and 53 known-etiology RPL, and 29 age-matched fertile controls were enrolled. Peripheral blood immunophenotype, NK cell cytotoxicity (NKC), and T-helper (Th) 1 and Th2 cytokine producing cell ratios (Th1/Th2) were measured using flowcytometry. The cutoff values were determined using Youden's J with likelihood ratio (LR) >2.

RESULTS

Natural killer cell percentage and NKC, TNF-α(+) Th1 cells, and TNF-α/IL-10 producing Th1/Th2 cell ratio were significantly higher in idiopathic RPL than controls. By the area under the curve (AUC) analysis, NK cell percentage (AUC = 0.691), NKC (AUC = 0.649), TNF-α(+) Th1 cells (AUC = 0.681) and Th1/Th2 cell ratio (AUC = 0.660) were highly specific for RPL. The cutoff values for NK cell percentage, NKC (E:T cell ratio 25:1), and TNF-α/IL-10 producing Th1/Th2 cell ratio are 16.1, 23.8, and 36.2%, respectively. Seventy-six percent of idiopathic RPL showed at least one of more immune abnormalities by these criteria.

CONCLUSION

Differences in NK cell percentages, NKC and Th1/Th2 cell ratio differentiated RPL from fertile controls.

New decision-tree model for defining the risk of reproductive failure

PROBLEM

Natural killer (NK) cells play a key role in embryo implantation and pregnancy success, whereas blood and uterine NK expansions have been involved in the pathophysiology of reproductive failure (RF). Our main goal was to design in a large observational study a tree-model decision for interpretation of risk factors for RF.

METHODS OF STUDY

A hierarchical multivariate decision model based on a classification and regression tree was developed. NK and NKT-like cell subsets were analyzed by flow cytometry.

RESULTS

By multivariate analysis, blood NK cells expansion was an independent risk factor for RF (both recurrent miscarriages and implantation failures). We propose a new decision-tree model for the risk interpretation of women with RF based on a combination of main risk factors.

CONCLUSIONS

Women with age above 35 years and >13% CD56⁺CD16⁺ NK cells showed the highest risk of further pregnancy loss (100%).

Role of NKp46 expression in cytokine production by CD56-positive NK cells in the peripheral blood and the uterine endometrium

PROBLEM

To investigate the role of natural cytotoxicity receptor, NKp46 expression in cytokine-producing NK cells.

METHOD OF STUDY

CD56(+) /NKp46(+) NK cells from the peripheral blood and the uterine endometrium were magnetically separated. IFN-γ, TNF-α, IL-4, IL-10, and TGF-β(1) expressions on NK cells were investigated using multicolor flow cytometry.

RESULTS

Peripheral blood and uterine endometrial NK cells were grouped into 4 subpopulations based upon the degree of CD56 and NKp46 expressions. NKp46 expression was associated with higher frequency of cytokine-producing NK cells, including CD56(dim) NK cells. The percentage of TNF-α(+) and IL-10(+) NK cells per total CD56(+) /NKp46(+) NK cells in the uterine endometrium showed a significant correlation with those of the peripheral blood in all subpopulations, but that of IFN-γ(+) , IL-4(+,) and TGF-β(1) (+) NK cells showed partial correlation.

CONCLUSION

Expression of NKp46 is involved in cytokine production of CD56(+) NK cells in the peripheral blood and the uterine endometrium.

Intravenous immunoglobulin treatment increased live birth rate in a Spanish cohort of women with recurrent reproductive failure and expanded CD56(+) cells

PROBLEM

Natural killer (NK, CD3(-)CD56(+)/CD16(+)) and NKT-like cells (CD3(+)CD56(+)/CD16(+)) activity is considered among the key factors for reproductive success. In the absence of immunological screening, beneficial effects of intravenous immunoglobulin (IVIG) in preventing recurrent reproductive failure (RRF) have not been reported. Here, we analyse the IVIG influence on pregnancy success in women with RRF and circulating NK or/and NKT-like cells expansion.

METHOD OF STUDY

One hundred fifty-seven women with previous recurrent miscarriage and/or recurrent implantation failure after in vitro fertilization were consecutively studied. Sixty-four patients with CD56(+) cell expansion, no apparent underlying disease and who maintained their desire to conceive were selected. Forty of them received IVIG during pregnancy.

RESULTS

Overall, the clinical pregnancy rate for the women under IVIG therapy was 92.5% and the live birth rate was 82.5%. Significantly lower pregnancy and live birth rates (25% and 12.5%, respectively) were observed for the patients with recurrent pregnancy loss and NK/NKT-like cells expansion without IVIG. After three cycles of IVIG, NK cell percentages decreased significantly and these values persisted throughout gestation.

CONCLUSION

Intravenous immunoglobulin therapy for women with RRF and NK or NKT-like cell expansion was a safe and beneficial therapeutic strategy that associated with high clinical pregnancy and live birth rates.

LIF and sIL-2R plasma concentrations in IVF patients on the day of embryo transfer: predictive markers of IVF outcome

Successful implantation is still the limiting step in IVF. We hypothesized that maternal plasma concentrations of certain cytokines at the time of embryo transfer could predict the likelihood of successful implantation and pregnancy. sIL-2R, IL-6, LIF, and MMP2 concentrations were measured in plasma from 160 IVF patients (natural and stimulated IVF cycles) on the morning of the embryo transfer (ET0) and 14 days later (ET+14). Patients were ultimately subdivided into four groups depending on the IVF treatment outcome (pregnancy failure, biochemical pregnancy, first-trimester miscarriage and normal term delivery). In natural and stimulated IVF cycles at ET0, sIL-2R concentrations were threefold higher in biochemical pregnancies than in pregnancy failures (P=0.020), and in natural cycles only, 2.5-fold higher in normal term deliveries than in pregnancy failures (P=0.023). Conversely, in natural and stimulated IVF cycles at ET0, LIF concentrations were one third lower in biochemical pregnancies/first-trimester miscarriages compared with pregnancy failures (P=0.042). We suggest that high sIL-2R and low LIF concentrations in maternal plasma on the morning of the embryo transfer might be associated with increased risks of early pregnancy loss, while a basal level of sIL-2R is necessary for normal term delivery outcome. Both cytokine measurements might therefore be useful in the management of IVF patients, and modulation of their concentrations could be investigated as a therapeutic alternative for women with abnormal concentrations at the time of embryo transfer.