Expression of Killer Immunoglobulin-like Receptors on Peripheral Blood NK Cell Subsets of Women with Recurrent Spontaneous Abortions or Implantation Failures

Management of recurrent implantation failure: British Fertility Society policy and practice guideline

Recurrent implantation failure (RIF) is defined as the absence of a positive pregnancy test after three consecutive transfers of good quality embryos. There remains significant variation in clinical practice in the management of RIF. This British Fertility Society (BFS) Policy and Practice guideline analyses the evidence for investigations and therapies that are employed in RIF and provides recommendations for clinical practice and for further research. Evidence for investigations of sperm and egg quality, uterine and adnexal factors, immunological factors and thrombophilia, endocrine conditions and genetic factors and for associated therapies have been evaluated. This guideline has been devised to assist reproductive medicine specialists and patients in making shared decisions concerning management of RIF. Finally, suggestions for research towards improving understanding and management of RIF have also been provided.

Natural killer cell profiles in recurrent pregnancy loss: Increased expression and positive associations with TACTILE and LILRB1

PROBLEM

NK cells are important for healthy pregnancy and aberrant phenotypes or effector functions have been associated with RPL. We compared expression of a broad panel of NK cell receptors, including immune checkpoint receptors, and investigated their clinical association with RPL as this might improve patient stratification and prediction of RPL.

METHOD OF STUDY

Peripheral blood mononuclear cells were isolated from 52 women with RPL and from 2 women with an uncomplicated pregnancy for flowcytometric analysis and plasma was used to determine anti-CMV IgG antibodies.

RESULTS

Between RPL and controls, we observed no difference in frequencies of T-, NKT or NK cells, in CD56dimCD16+ or CD56brightCD16- NK cell subsets or in the expression of KIRs, NKG2A, NKG2C, NKG2D, NKp30, NKp44, NKp46 or DNAM1. NK cells from women with RPL had a higher expression of LILRB1 and TACTILE and this was associated with the number of losses. The immune checkpoint receptors PD1, TIM3 and LAG3 were not expressed on peripheral blood NK cells. In RPL patients, there was a large variation in NKG2C expression and higher levels could be explained by CMV seropositivity.

CONCLUSION

Our study identified LILRB1 and TACTILE as NK cell receptors associated with RPL. Moreover, we provide first support for the potential role of CMV in RPL via its impact on the NK cell compartment. Thereby our study could guide future studies to confirm the clinical association of LILRB1, TACTILE and NKG2C with RPL in a larger cohort and to explore their functional relevance in reproductive success.

Allogeneic lymphocytes immunotherapy in female infertility: Lessons learned and the road ahead

The endometrium is an essential tissue in the normal immunologic dialogue between the mother and the conceptus, which is necessary for the proper establishment and maintenance of a successful pregnancy. It's become evident that the maternal immune system plays a key role in the normal pregnancy's initiation, maintenance, and termination. In this perspective, the immune system contributes to regulating all stages of pregnancy, thus immunological dysregulation is thought to be one of the major etiologies of implantation failures. Many researchers believe that immune therapies are useful tactics for improving the live births rate in certain situations. Lymphocyte immunotherapy (LIT) is an active form of immunotherapy that, when used on the relevant subgroups of patients, has been shown in multiple trials to dramatically enhance maternal immunological balance and pregnancy outcome. The primary goal of LIT is to regulate the immune system in order to create a favorable tolerogenic immune milieu and tolerance for embryo implantation. However, there are a plethora of influential factors influencing its therapeutic benefits that merit to be addressed. The objective of our study is to discuss the mechanisms and challenges of allogeneic LIT.

Killer-cell immunoglobulin-like receptor/human leukocyte antigen-C combination and 'great obstetrical syndromes' (Review)

Recurrent pregnancy loss (RPL), pre-eclampsia (PE), fetal growth restriction (FGR), and preterm delivery are examples of ‘great obstetrical syndromes’ (GOS). Placental dysfunction is the most common pathogenesis of GOS. In human pregnancies, the effects of uterine natural killer cells involve angiogenesis, promoting the remodeling of uterine spiral artery, and improving the invasion of trophoblast cells. The uNK cells supply killer immunoglobulin-like receptors (KIRs), which come into contact with human leukocyte antigen-C (HLA-C) ligands expressed by extravillous trophoblast cells (EVTs). Numerous studies have investigated the association between GOS and KIR/HLA-C combination. However, the outcomes have not been conclusive. The present review aimed to reveal the association between GOS and KIR/HLA-C combination to screen out high-risk pregnancies, strengthen the treatment of pregnancy complications, and reduce the frequency of adverse maternal and fetal outcomes. It has been reported that a female with a KIR AA genotype and a neonate with a paternal HLA-C2 molecule is more prone to develop GOS and have a small fetus since less cytokines were secreted by uNK cells. Conversely, the combination of KIR BB haplotype (including the activating KIR2DS1) and HLA-C2 can induce the production of cytokines and increase trophoblast invasion, leading to the birth of a large fetus. KIR/HLA-C combinations may be applicable in selecting third-party gametes or surrogates. Detection of maternal KIR genes and HLA-C molecules from the couple could serve as useful markers for predicting and diagnosing GOS.

Changes of dendritic cell and natural killer cell on the cord blood with idiopathic fetal growth restriction

OBJECTIVE

To investigate the characteristics of dendritic cells (DC) and natural killer cells (NK) in umbilical cord blood of pregnant patients diagnosed with idiopathic fetal growth restriction (IFGR).

METHODS

A prospective study cohort of IFGR patients was established who were in the third trimester (28-36 weeks), with a healthy, pregnant woman cohort selected as controls. Umbilical cord blood was collected.

RESULTS

The study included 50 pregnant women in the IFGR group and 50 pregnant women in the healthy, control group. The incidence of SGA in the IFGR group was 52.0%, and the incidence of preterm birth was 18.0%. The incidence of neonatal complications in neonates with live birth in the IFGR group was 12.0%. The birth weight, body length and placental weight of the newborns in the IFGR group were significantly lower than those in the control group (p < .05). Flow cytometry revealed no significant difference in the proportion or maturity of DC in umbilical cord blood between IFGR group and control group (p > .05). The proportion of NK cells in umbilical cord blood of IFGR group was significantly higher than that of normal control group. The proportion of CD56dimCD16+ NK cells was also significantly higher than that of the normal control group (p < .05), but the expression of NK cell surface killing activator receptor NKG2D and inhibitory receptor NKG2A was not statistically significant (p > .05).

CONCLUSION

The number and proportion of DC cells in cord blood may not be the key factors affecting the outcomes observed during FGR pregnancies. However, we found the proportion of NK cells in cord blood to be significantly increased, as well as the ratio of CD56dimCD16 + NK to CD56highCD16-NK to be imbalanced, which may be one of the pathogenesis of the pathological pregnancy leading to IFGR.

Natural killer frequency determines natural killer cytotoxicity directly in accentuated zones and indirectly in "moderate-to-normal frequency" segment

Natural killer (NK) frequency and NK cytotoxicity (NKc) are key determining factors of a clinical outcome. In our previous study, we showed the prognostic clinical significance of immune parameters when they are beyond the optimal range (accentuated). In this study, we attempted to explain the disparity of accentuated but physiologically and immunologically normal NK parameters that might serve as negative clinical prognostics indications of failed pregnancies. We have analyzed NK%, NKc levels, and their reciprocal correlation in 2,804 patients with reproductive failures. In the entire clinical population, NK% correlates with NKc. Interestingly, we found this relationship to be strongly dependent on NK level's status. NK%-NKc correlation was the strongest (r = 0.2021, p < 0.0001) in a patient group with high NK% (> 17.5%). Patients with NK% between 15-17.5% manifested lower but still significant correlation NK%-NKc (r = 0.1213, p = 0.0155). Additionally, significant correlation (r = 0.2689, p < < 0.0001) between NK% and NKc was observed in a group of patients with NK levels < 7% (1.7-7%). While patients' groups with NK% (7-15%) did not reveal NK%-NKc association. This led us to hypothesize that the qualitative-quantitative status of NK population is responsible for their cytotoxic activity. Consistent with our hypothesis, the "balanced zone" NK% is tightly controlled, and thus does not correlate directly with NKc. In contrast, the "accentuated zones" of NK% escape this control and directly affecting NKc. Demonstrated phenomena supports our idea about the clinical significance of immune accentuation and explains its novel physiological role.

Decreased HLA-C1 alleles in couples of KIR2DL2 positive women with recurrent pregnancy loss

Specific killer cell immunoglobulin-like receptor (KIR) in women with recurrent pregnancy loss (RPL) and HLA ligands in couples invoke a susceptibility to RPL. However, the relationship between KIR2DL2 and its cognate ligand HLA-C1 has not been explored. In this prospective cohort study, 160 Caucasian women with RPL and 99 partners were included. KIR/HLA-C typing, NK assay, Th1/Th2 intracellular cytokine ratios, 25-(OH)-vitamin D level, and the presence of autoantibodies were analyzed. KIR2DL2 positive women (P = 0.023) and their partners (P = 0.017) had lower allele frequencies of HLA-C1 than those of KIR2DL2 negative women. KIR2DL2 positive women had significantly lower genotype frequency of HLA-C1C1 as compared to the North American Caucasian population controls (P < 0.05). In the partners of KIR2DL2 positive women, there was a substantially higher frequency of HLA-C2C2 than controls (P = 0.016). Besides, KIR2DL2 negative women had a higher prevalence of anti-ssDNA antibody as compared with that of KIR2DL2 positive women (P = 0.043). There were no differences in the distribution of HLA-C genotypes based on KIR2DL2, regardless of pregnancy outcome in women with RPL and their partners while on immunomodulation treatment. In conclusion, decreased ligands for inhibitory KIRs (inhKIR) could lead to insufficient inhibition of maternal uterine NK cells toward the trophoblast, thereby contributing to the pathogenesis of RPL. Specific KIR and HLA-C genotyping may predict the reproductive outcome of women with RPL.

Concordance between peripheral and decidual NK cell subsets and killer immunoglobulin-like receptors in women with recurrent spontaneous miscarriages

BACKGROUND

The role of decidual natural killer (dNK) cells in normal and complicated pregnancy and their relation with peripheral NK (pNK) cells remains unclear. The study aim was phenotypic analysis of pNK and dNK cells at time of miscarriage in recurrent spontaneous miscarriage (RSM) patients to assess whether measuring levels of pNK cell populations can reflect changes in dNK cells or not.

METHODS

This study included 40 middle aged pregnant women in the 1st trimester subjected to evacuation because of a current miscarriage. They had a history of previous ≥ two unexplained miscarriages. Frequencies of pNK and dNK cells, based on the expression of CD56, CD16, inhibitory (CD158b) and activating (CD161) Killer immunoglobulin-like receptors (KIRs), were detected by flow cytometry.

RESULTS

Percentages of CD56⁺ NK cells in peripheral blood and decidua were 17.5 % and 17.3 %, respectively. In both blood and decidua, CD56^dim NK cells were exceeding CD56^bright NK cells. The CD56^dim CD16^- NK cells were the predominating subset of NK cells, followed by CD56^dim CD16^dim. No substantial differences were detected in the levels of KIRs expression by the different NK subsets between blood and decidua. Abnormal up-regulation of both CD161 and CD158b on NK cells was observed in blood and decidua.

CONCLUSION

At the time of miscarriage, patients with RSM have an extremely active immune system and an increased number of toxic NK cells both in blood and decidua. The pNK cells reflect dNK cell changes during miscarriage and may be a useful non-invasive predicting tool in reproductive failure setting.

Altered Immune Response and Implantation Failure in Progesterone-Induced Blocking Factor-Deficient Mice

Earlier data suggest that progesterone-induced blocking factor (PIBF) is involved in implantation. The present study therefore aims to investigate the consequences of functional PIBF deficiency during the peri-implantation period. CD1 female mice were injected intraperitoneally with 2 μg anti-PIBF monoclonal antibody on days 1.5 and 4.5 of pregnancy. The number of implantation sites and resorption rates were recorded on day 10.5. PIBF+ decidual NK cells and B cells were detected by immunohistochemistry or immunofluorescence. Decidual and peripheral NK activity was assessed by flow cytometry. A prime PCR array was used for determining the differential expression of genes involved in lymphocyte activation and Th1 or Th2 differentiation in CD4+ and CD8+ spleen cells from pregnant anti-PIBF-treated and control mice. Anti-PIBF treatment in the peri-implantation period resulted in impaired implantation and increased resorption rates in later pregnancy. The number of PIBF+ decidual NK cells decreased, while both decidual and peripheral NK activity increased in the anti-PIBF-treated mice. B cells were absent from the resorbed deciduas of anti-PIBF-treated mice. The genes implicated in T cell activation were significantly downregulated in CD4+ and increased in CD8+ of the anti-PIBF-treated animals. The gene for IL-4 was significantly downregulated in CD4+ cells while that of IL-12A was upregulated in CD8+ cells of anti-PIBF-treated animals. These data suggest that the lack of PIBF results in an impaired T cell activation, together with Th1 differentiation and increased NK activity, resulting in implantation failure.

Comparison of T and NK lymphocyte subsets between human endometrial tissue and peripheral blood

Immune profiles in endometrium may be changed in patients with IVF failure and its possible correlations with immune parameters in peripheral blood are important for the diagnostic approach. Such correlations in healthy women are unknown and have been studied in the present research. The expression of CD56, CD158a, HLA DR, CD69 in T lymphocytes, CD4 T lymphocytes, CD8+ T lymphocytes and NK cells were studied by flow-cytometry in endometrium and peripheral blood in healthy 24 donors of oocytes aged 25-32 years. Levels of T lymphocyte and T helper cells were lower in endometrium and no differences in CD8 T lymphocytes were registered between endometrium and peripheral blood. The expression of HLA DR and especially CD69 was higher in CD3, CD4, CD8 T cells in endometrium in comparison with peripheral blood. The endometrium lymphocyte population was enriched by NK cells that were generally CD56++ with a higher expression of HLA DR and almost in total were CD69 positive. Strong positive correlations of CD8 expression in NK cells (r = 0.6478, p < 0.001) and HLA DR expression in CD8 T cells (r = 0.6107, p < 0.01) between peripheral blood and endometrium were registered in fertile women. The endometrial CD56 expression in CD8+ T cells negatively correlated with endometrial CD8 expression in NK cells (r = -0.5252, p < 0.01) which possibly reflected a suppressive and regulating mechanism in the endometrium. CD8+ NK cells and HLA DR+ CD8 T cells in endometrium were related to the same subsets in peripheral blood.

NK cell frequency and cytotoxicity in correlation to pregnancy outcome and response to IVIG therapy among women with recurrent pregnancy loss

BACKGROUND

Recurrent miscarriage (RM) has a multifactorial etiology mainly due to chromosomal abnormalities and immunological factors. Treating RM has remained to be a challenging issue and the role of intravenous immunoglobulin (IVIG) in treating RM is still controversial.

MATERIALS AND METHODS

This study aimed to evaluate the changes in natural killer (NK) cells' frequency and cytotoxicity in patients with RM who received the IVIG therapy. A total of 78 women with a history of three or more recurrent miscarriages were included and their peripheral blood was drawn in case of positive pregnancy test. On the same date, 400 mg/kg of IVIG was administrated intravenously in 38 women and it continued every four weeks through weeks 30-32 of gestation. The remaining 40 patients with RM were included to be the untreated control group. Then, the effects of IVIG on NK cell frequency, cytotoxic activity, and the expression of inhibitory and activating receptors in the patients with RM, pre and posttreatment were assessed.

RESULTS

NK cells percentage and cytotoxicity were significantly reduced in the IVIG-treated patients after 32 weeks of gestation (p < 0.0001). Expression levels of inhibitory receptors was increased, however, the expression levels of activating receptors were significantly decreased after the IVIG therapy. Pregnancy outcome after the treatment was significantly higher (86.8%) in the IVIG-treated patients than controls (45%; p = 0.0006).

CONCLUSION

Our results suggested that women with RM may benefit from IVIG as a therapeutic approach and the frequency and functional status of peripheral NK cells may serve as a valuable predictive factor of therapy response.

Increased natural killer cell subsets with inhibitory cytokines and inhibitory surface receptors in patients with recurrent miscarriage and decreased or normal subsets in kidney transplant recipients late post-transplant

Patients with recurrent miscarriage (RM) show up-regulated cytotoxic natural killer (NK) cells that are suspected to play a causal role in abortion. In the present study, we investigated counter-regulating inhibitory mechanisms and compared the results in RM patients with those of healthy controls (HC), patients with end-stage renal disease (ESRD) and kidney transplant recipients late post-transplant (TX). NK, NK T and T cell subsets were analysed in the peripheral blood of 31 RM, 14 female ESRD and nine female TX patients as well as 21 female HC using eight-colour fluorescence flow cytometry. Compared with HC, RM patients showed significantly higher absolute numbers of CD56⁺ NK cells co-expressing the phenotype interferon (IFN)-γR⁺ , IL-4⁺ , transforming growth factor (TGF)-β⁺ , IL-4⁺ human leucocyte antigen D-related (HLA-DR)⁺ , TGF-β⁺ HLA-DR⁺ , IL-4⁺ TGF-β⁺ , IL-4⁺ TGF-β^- , IFN-γ⁺ and/or IL-10^- IFN-γ⁺ (all P ≤ 0·01), more IL-17⁺ CD56^bright (P = 0·028) NK cells and more CD56^dim CD16⁺ NK cells co-expressing IFN-γR, IFN-γ, IL-4 and/or TGF-β (all P ≤ 0·01). When the same cell subsets were analysed in ESRD or TX patients, cytokine-producing NK cell subsets were not significantly different from those of HC. RM patients showed significantly higher absolute numbers of CD158a⁺ , CD158b⁺ , CD158a^- CD158e⁺ (all P < 0·05), NKG2D⁺ NKG2A⁺ , NKG2D ⁺ NKG2A^- , NKG2D⁺ and/or NKG2A⁺ (all P ≤ 0·01) CD56⁺ NK cells and higher CD158a⁺ , CD158b⁺ (all P < 0·05), NKG2D⁺ and/or NKG2A⁺ (all P < 0·01) CD56^dim+ CD16⁺ NK cells than HC. In contrast, ESRD patients had normal and TX recipients had lower CD158a⁺ and NKG2D⁺ NKG2A^- CD56⁺ NK cells and lower CD158a⁺ CD56^dim+ CD16⁺ NK cells (all P < 0·05) than HC. RM patients have abnormally high circulating NK cells expressing inhibitory cytokines and inhibitory surface receptors which might contribute to the pathogenesis of RM.

Lymphocytes in Placental Tissues: Immune Regulation and Translational Possibilities for Immunotherapy

Immune modulation at the fetomaternal interface is crucial to ensure that the fetal allograft is not rejected. In the present review, the focus is to describe basic functions of lymphocyte populations and how they may contribute to fetomaternal immune regulation, as well as determining what proportions and effector functions of these cells are reported to be present in placental tissues in humans. Also explored is the possibility that unique cell populations at the fetomaternal interface may be targets for adoptive cell therapy. Increasing the understanding of immune modulation during pregnancy can give valuable insight into other established fields such as allogeneic hematopoietic stem cell transplantation and solid organ transplantation. In these settings, lymphocytes are key components that contribute to inflammation and rejection of either patient or donor tissues following transplantation. In contrast, an allogeneic fetus eludes rejection by the maternal immune system.

Correlation between unexplained recurrent spontaneous abortion with CD4+CD25+ regulatory T-cell and killer cell immunoglobulin-like receptor levels

The present study investigated the correlation between unexplained recurrent spontaneous abortion (URSA) with CD4+CD25+ regulatory T-cell (Treg) and killer cell immunoglobulin-like receptor (KIR)-2DL1 levels. A total of 76 URSA patients were enrolled (35 without pregnancy, Group A, and 41 with early abortion, Group B). Additionally, 30 patients who received a regular abortion as planned (Group C) and 30 healthy volunteers (Group D) were selected. Peripheral venous blood and fresh decidual tissue samples were obtained from all the patients, and flow cytometry was performed to detect CD4+CD25+Treg and Foxp3 transcription factor levels. mRNA and protein KIR-2DL1 expression levels were assayed using quantitative PCR and western blot analysis, respectively. No statistically significant differences in peripheral venous blood CD4+CD25+Treg/CD4+ and Foxp3+/CD4+CD25+Treg cell proportions were found among the groups (P>0.05). However, the decidual tissues of Group C presented significantly higher levels of both cell types versus other groups (P<0.05). No statistically significant differences were found in comparisons among Groups A, B, and D (P>0.05). In peripheral venous blood, mRNA and protein KIR-2DL1 expression levels in Group C were significantly higher than those in the other three groups (P<0.05), but again, there were no statistically significant differences among Groups A, B, and D (P>0.05). In decidual tissues, KIR-2DL1 levels were significantly higher in Group C relative to Groups A, B, and D (P<0.05). Decreased CD4+CD25+Treg counts and KIR-2DL1 expression levels were closely associated with the onset of URSA. CD4+CD25+Tregs mainly exert their effects on decidual tissues, while KIR-2DL1 can act on peripheral venous blood and decidual tissues. These may present new targets for early intervention in URSA.

The "killer cell story" in recurrent miscarriage: Association between activated peripheral lymphocytes and uterine natural killer cells

Peripheral and uterine NK cells (pNK, uNK) can be distinguished according to their receptor expression. Recent studies indicate an association of elevated pNK and uNK with recurrent miscarriage (RM). This study aimed to analyze pNK and uNK in patients with RM and healthy controls. Out of n=590 RM patients screened according to a standard diagnostic protocol, n=268 couples with ≥3 consecutive RM were identified. Subgroups consisted of n=151 primary RM (pRM), n=85 secondary RM (sRM), n=32 tertiary RM (tRM) and n=42 healthy controls. Finally, n=147 idiopathic RM (iRM) and n=121 non-iRM patients were identified. Peripheral blood levels of CD45+CD3-CD56+CD16+ NK cells were determined in non-pregnant patients and controls in the mid-luteal phase by FACS. In n=129 RM patients a uterine biopsy was taken to evaluate CD56+ NK cells by immunohistochemistry. PRM showed higher absolute pNK than sRM (median/μl (Q1;Q3): 234 (147;306) vs 176 (128;245), p=0.02). Further a trend towards higher pNK percentages in pRM was detected. UNK numbers did not differ between RM subgroups and did not correlate with pNK. However, the rate of highly elevated uNK was increased in iRM compared to non-iRM patients (p=0.04). Further, higher numbers of CD45+CD3-DR+ (p<0.01) and CD45+CD3+CD8+DR+ (p=0.04) peripheral lymphocytes were associated with higher uNK numbers. In conclusion, elevated pNK were present in pRM patients. Although pNK and uNK numbers did not correlate, the association between high CD45+CD3-DR+ and CD45+CD3+CD8+DR+ peripheral lymphocytes and uNK might indicate that activated NK, B and T cells provide cytokines for the differentiation of uNK.

1,25-Dihydroxy-vitamin D3 regulates NK-cell cytotoxicity, cytokine secretion, and degranulation in women with recurrent pregnancy losses

Vitamin D has a pivotal role in regulating immune responses by promoting Th2 immune responses and suppressing Th1 responses. Propensities to a Th1 immune response and increased NK-cell levels and cytotoxicity have been reported in women with recurrent pregnancy losses (RPL). In women with RPL, vitamin D deficiency is prevalent; however, the effect of vitamin D on NK cells is largely unknown. In this study, we demonstrated that CD69(+) activating receptor expression on NK cells was significantly decreased by incubation with 1,25(OH)2 D3 in a dose-dependent manner, while CD158a and CD158b inhibitory receptor expression was upregulated. The degranulation marker CD107a was significantly downregulated on NK cells following incubation with 1,25(OH)2 D3 . NK-cell conjugation with K562 target cells was not affected by 1,25(OH)2 D3 ; however, depolarization of perforin granules in conjugated NK cells was significantly increased. TLR4 expression on NK cells was significantly decreased and TNF-α and IFN-γ production was significantly reduced by 1,25(OH)2 D3 through interference with NF-κB. Our results suggest 1,25(OH)2 D3 has immune regulatory effects on NK cell cytotoxicity, cytokine secretion and degranulation process as well as TLR4 expression. Potential therapeutic application of 1,25(OH)2 D3 for dysregulated NK-cell immunity should be explored in the future.

Potentiation of cytokine-induced proliferation of human Natural Killer cells by intravenous immunoglobulin G

Intravenous IgG (IVIG) therapy can be used for immunomodulation. IL-2 is an immunoregulatory cytokine. We evaluated IVIG modulation of human blood lymphocyte response to IL-2 and other cytokines. Neither IVIG nor low concentrations of IL-2 (3-30U/ml) induced lymphocyte proliferation, but in combination they synergistically enhanced proliferation of NK cells. The CD56(bright) cells expanded more than CD56(dim) NK cells, with 90% of NK cells dividing up to 8 generations by day 6, while <8% of T cells divided. IVIG also potentiated NK cell proliferation with IL-12, IL-15 and IL-18. The IVIG+cytokine-expanded NK cells were less cytotoxic for K562 cells, than NK cells with cytokine alone. IVIG also enhanced interferon-γ production with IL-2, IL-12 and IL-18. In conclusion, IVIG selectively potentiates NK cell proliferation and interferon-γ secretion with IL-2, IL-12, IL-15 and IL-18 in vitro. These findings warrant evaluation in vivo in relation to NK cells and the immunoregulatory actions of IVIG.

Comparative analysis of NK cell subsets in menstrual and peripheral blood of patients with unexplained recurrent spontaneous abortion and fertile subjects

Natural killer (NK) cells play a fundamental role in maintaining pregnancy. Based on the availability and non-invasive method of collection of menstrual blood (MB), here we investigated for the first time a comparative analysis of NK cell subsets in MB and peripheral blood (PB) of women with recurrent spontaneous abortion (RSA) and fertile women. PB and MB of healthy fertile (n=15) and RSA women (n=15) were sampled simultaneously on the second day of the menstrual cycle. Proportions of CD56+CD3-CD16+/-, CD56+CD3-CCR7+/-, and CD56+CD3-CD45RO+/- cells were analyzed using flow cytometry. In the MB of both groups, proportions of CD16+ and CD45RO- NK cells were significantly lower than in the PB. In parallel, CD56+CD16+CCR7- and CCR7+ cells were present in significantly smaller amounts in MB than in PB. However, the amounts of CD56+CD16-CCR7- and CCR7+ cells were greater in MB. In comparison to the fertile group, the percentage of MB CD45RO+ NK cells was significantly lower and frequencies of PB CD16-, CD45RO- and CD56+CD16+CCR7+ subsets were significantly higher in RSA patients. Different subsets of NK cells are differentially distributed in MB in comparison with PB in women with RSA and fertile subjects. Population differences of NK cell subsets in RSA patients and normal controls were more clearly reflected at the systemic level.

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.

Characterization of the Th profile of the bovine endometrium during the oestrous cycle and early pregnancy

Despite extensive research in the area of cow fertility, the extent to which the maternal immune system is modulated during pregnancy in cattle remains unclear. Therefore, the objective of the current study was to characterize the presence and response profile of B, T-helper (LTh), T- cytotoxic (LTc), gamma delta-T (γδT) and natural killer (NK) lymphocytes in terms of cell number, distribution and cytokine expression in bovine endometrial tissue to pregnancy. Endometrial tissue samples were collected from beef heifers on Days 5, 7, 13 and 16 of the estrous cycle or pregnancy. Samples were analysed by immunofluorescence to identify the presence and abundance of B-B7 (B-cells), CD4 (LTh), CD8 (LTc), γδT cell receptor (TCR) and CD335/NKp46 (NK cells) -positive immune cells. Quantitative real time PCR (QPCR) was carried out to analyse mRNA relative abundance of FOXP3 (a marker of regulatory T (Treg) cells) and a panel of immune factors, including MHC-I, LIF, Interleukins 1, 2, 6, 8, 10, 11,12A, IFNa and IFNG. Results indicate that B-B7+ cells are quite populous in bovine endometrial tissue, CD4+ and CD8+ -cells are present in moderate numbers and γδTCR+ and CD335+ cells are present in low numbers. Pregnancy affected the total number and distribution pattern of the NK cell population, with the most significant variation observed on Day 16 of pregnancy. Neither B lymphocytes nor T lymphocyte subsets were regulated temporally during the oestrous cycle or by pregnancy prior to implantation. mRNA transcript abundance of the immune factors LIF, IL1b, IL8 and IL12A, IFNa and IFNG, expression was regulated temporally during the estrous cycle and LIF, IL1b, IL-10, IL11, IL12A were also temporally regulated during pregnancy. In conclusion, the endometrial immune profile of the oestrous cycle favours a Th2 environment in anticipation of pregnancy and the presence of an embryo acts to fine tune this environment.

Immune etiology of recurrent pregnancy loss and its diagnosis

Recurrent Spontaneous Abortion of Immunological Origin (RSAI) is currently diagnosed by the occurrence of 2-3 consecutive miscarriages of unknown origin. The psychological trauma incurred by these events is a serious ailment which may be potentially avoided if a method of analysis is derived which may forecast these events and in turn prevent them from occurring. This review intends to examine studies of recurrent spontaneous abortion (RSA) which use laboratory diagnosis and also studies of RSA that do not use laboratory diagnosis. We believe that when laboratory results are incorporated into the diagnosis of RSA/RSAI that treatment is highly successful whereas the absence of laboratory results severely hinders the effectiveness of treatment. It is worth noting that correlating treatment versus outcome is imprudent because of the multiple variables involved in patient cases. It is not imprudent, however, to say that incorporation of laboratory data is essential when diagnosing RSA/RSAI.

Recent advances in understanding immunology of reproductive failure

Aspects of the immunological relationship between mother and conceptus still remain a mystery, although the recent advances in molecular biology have enlightened some of the parameters that participate in fetomaternal cross-talk during implantation. The atypical expression of major histocompatibility complex (MHC), the specific role of some hormones and cytokines, as well as the temporal and spatial distributions of uterine natural killer cells, represent substantive parameters of fetomaternal immunotolerance during implantation. Although human maternal and fetal immunology is difficult to investigate, aberrant immune responses and an imbalanced cytokine network may be related to infertility, implantation failures after IVF and recurrent pregnancy losses. In this review, immunological and interacting factors involved in human reproductive failure are summarized and critically evaluated.

Progesterone-mediated immunomodulation in pregnancy: its relevance to leukocyte immunotherapy of recurrent miscarriage

Progesterone is crucial for the establishment and maintenance of pregnancy. Progesterone-regulated genes in the pregnant uterus control the development of endometrial receptivity as well as recruitment and differentiation of decidual NK cells, which in turn act on angiogenesis and trophoblast invasion. The link between progesterone and the immune system is established by lymphocyte progesterone receptors expressed in peripheral blood gammadelta T cells of pregnant women and in peripheral NK cells. Regulation of lymphocyte progesterone receptors is activation related, thus efficient recognition of fetal antigens is a requirement for the initiation of progesterone-dependent immunoregulatory mechanisms. Several immunological effects of progesterone are mediated by progesterone-induced blocking factor--the product of a progesterone-induced gene in lymphocytes. One part of unexplained recurrent miscarriages might have an immunological etiology. Immunization of the mothers with paternal or third-party leukocytes aims to correct the misregulated antifetal immune response. There are, however, serious concerns about this treatment, including the lack of information about the mode of action and possible adverse effects of the treatment, the failure to detect a significant effect of immunotherapy and the lack of a reliable generally accepted marker for patient selection. These concerns will be discussed in this review.

Novel aspects of in vitro IL-2 or IFN-α enhanced NK cytotoxicity of healthy individuals based on NKG2D and CD161 NK cell receptor induction

As IL-2 and IFN-α modulate NK cell activity it was of interest to investigate the expression of newly defined NK cell receptors and augmented NK cell activity in healthy individuals after cytokine in vitro treatment. Peripheral blood lymphocytes (PBL) obtained from 31 healthy volunteers treated for 18 h with 200 IU/ml IL-2 and 250 IU/ml IFN-α were evaluated for NK cell cytotoxicity. Expression of NKG2D, CD161, CD158a, CD158b receptors was analyzed on CD3⁻CD16+ NK cells, cytotoxic CD16(bright) and regulatory CD16(dim) subsets by FACS flow. The found induced significant in vitro enhancement of NK cell activity by both cytokines is supported by specific cytokine induction in PBL of pSTAT1 and pSTAT5, determined by Western blotting, as well as induction of IRF-1 transcription. Both cytokines induce significant up-regulation of NKG2D expression while only IFN-α induced significant up-regulation of CD161, with no alteration in KIR expression by either cytokine on CD3⁻CD16+ NK cells. Investigated cytokines did not induce change in NK cell bright and dim subset distribution. Moreover, we find that, not only cytokine receptor induction on the CD3⁻CD16+ NK cells, but also simultaneous increase in their percentage and/or density on CD16(bright) and CD16(dim) subsets, represent good indicators of receptor cytokine-susceptibility. As the role of NK cells has been shown in the loss of tolerance, infection and cancer, the data obtained in this study may be of help in NK cell profiling, by giving referent values of cytokine-induced novel NK cell receptor expression either in evaluation of these diseases or in immunomonitoring during cytokine immunotherapy.

Fetal rejection: infertility and immunity

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

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

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

Elevated NK cell cytotoxicity, CD158a expression in NK cells and activated T lymphocytes in peripheral blood of women with IVF failures

PROBLEM

The aim of this study was to evaluate the role of elevated natural killer cytotoxicity (NKc) in women with multiple implantation failures (IF) in vitro fertilization-embryo transfer (IVF-ET) cycles.

METHODS OF STUDY

Seventy-nine antiphospholipid antibodies-negative women with IF including 33 women with elevated NKc were selected for investigation. K-562 cell line was used to evaluate NKc. Lymphocyte subsets, intracellular cytokines [interferon (IFN)-gamma, interleukin (IL)-4, tumour necrosis factor, IL-10], expression of activating markers [CD69, human leukocyte antigen (HLA)-DR], CD8, KIR (CD158a), CD95, and chemokine receptors (CXCR3, CCR4) were estimated by flow cytometry.

RESULTS

In women with IF, levels of NKc were higher than in IVF successful women. IF was associated with higher expression of CD8, CD158a, and HLA-DR in NK cells, activating markers in T lymphocytes, and lower levels of CCR4+ and IL-4+ T lymphocyte subsets. Predictive value of single elevated NKc for IVF success was 0.85, but addition of two other abnormal parameters resulted in its decrease to <0.39.

CONCLUSIONS

Elevated NKc is negative factor, though not critical for implantation in IVF cycles. Immune mechanism of IVF failure includes not only elevated NKc but also some other factors, such as elevated expression of CD8 and CD158a on NK cells, T lymphocyte activation, and diminished T helper 2 parameters.

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

PROBLEM

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

METHOD OF STUDY

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

RESULTS

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

CONCLUSION

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

The role of decidual natural killer cells in normal placentation and in the pathogenesis of preeclampsia

Adequate invasion of the human placenta during the first weeks of pregnancy is a critical step in ensuring both fetal and maternal health. A rapidly expanding body of evidence suggests that decidual natural killer (dNK) cells, a distinct population of CD56brightCD16- lymphocytes, are key regulators of this complex process. Experiments using murine models and in vitro evidence using human tissue cultures suggest that dNK cells modulate extravillous trophoblast (EVT) invasion and remodelling of maternal spiral arteries via both contact-dependent and contact-independent mechanisms. In addition, the differential expression of surface receptors by dNK cells may have a role in determining reproductive success through modulation of the maternal immune system at the time of implantation and placentation. The roles of cytokines, chemokines, and growth factors secreted by dNK cells and their influence on EVT migration, invasion, and pseudovasculogenesis are of particular interest. We reviewed the available experimental evidence related to the functional relationships between dNK cells and trophoblasts at the time of placentation to elucidate potential clinical correlations with human pathologies, including preeclampsia, recurrent pregnancy loss, IVF failure, and placenta accreta.

Clinical implication of natural killer cells and reproduction

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

Intracellular cytokine expression of peripheral blood natural killer cell subsets in women with recurrent spontaneous abortions and implantation failures

OBJECTIVE

To investigate the cytokine expression by peripheral blood natural killer (NK) cells of women with recurrent spontaneous abortion (SAB) or implantation failures.

DESIGN

Prospective cohort study.

SETTING

University clinic.

PATIENT(S)

Twenty-five women with recurrent SAB, 20 women with implantation failures, and 15 healthy controls.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Cytokine expression (interferon-gamma, tumor necrosis factor [TNF]-alpha, interleukin [IL]-4, IL-5, IL-10, IL-13, granulocyte-macrophage colony-stimulating factor [GM-CSF]) in NK cells and their subsets (CD56(dim) and CD56(bright)).

RESULT(S)

Proportion (percentage) of CD56(bright)/interferon-gamma(+)/TNF-alpha(+) cells was significantly higher in women with recurrent SAB and implantation failures as compared with that of healthy controls. Proportion of CD56(bright)/IL-4(+)/IL-10(+) cells was very low (<2%) in all groups but was significantly lower in women with recurrent SAB than that of controls. The TNF-alpha/GM-CSF expressing CD56(bright) cell ratio was significantly higher in women with recurrent SAB and implantation failures than in controls.

CONCLUSION(S)

Natural killer-1 shift in peripheral blood NK cells was identified in nonpregnant women with recurrent SAB and implantation failures. Tumor necrosis factor-alpha/GM-CSF expressing CD56(bright) cell ratio can be applicable for the diagnosis of recurrent SAB or implantation failures. Further studies are needed as to whether cytokine expression of NK cells during pregnancy can affect pregnancy outcome.

14th International HLA and Immunogenetics Workshop: Report from the reproductive immunology component

The aim of the study was to investigate whether human leukocyte antigen (HLA) allele sharing between partners or the maternal killer immunoglobulin-like receptor (KIR) repertoire is associated with recurrent spontaneous abortion (RSA) and repeated implantation failure after in vitro fertilization (IVF)/embryo transfer. From a total population of 158 RSA couples, 40 couples with repeated implantation failures (IVF) and 81 control couples, reported by five different laboratories, analysis was performed for (a) HLA sharing in 50 RSA, 31 IVF and 31 control couples, (b) DQA1*0505 sharing/homozygosity among partners in 108 RSA, 40 IVF and 36 control couples, and (c) the women's KIR repertoire in 46 RSA, 26 IVF and 36 control wives. RSA couples were divided into alloimmune aborter (RSAallo) and autoimmune aborter (RSAauto). The results oppose to the suggestion that increased HLA sharing per se or a limited maternal KIR repertoire predisposes to RSA or IVF failure. However, the observation of a slightly higher percentage of DQA1*0505 sharing in the RSAauto and the IVF group needs further investigation. The ratio of inhibitory to activating KIR (actKIR) was slightly lower in RSAallo and IVF women (1.9 vs 2.6 in controls), while in a high percentage of these women, the standard receptors of the KIR A haplotype were combined with actKIR/s of the haplotype B (66.6% and 45.4% vs 20% and 15.3% in RSAauto and control groups). This may suggest a possible involvement of actKIRs in embryo implantation and the maintenance of pregnancy and also requires further investigation.

Immune cells in uteroplacental tissues throughout pregnancy: a brief review

In a brief introduction, this review states why the presence of immune cells at the interface poses problems for an immunologist (Medawar paradigm). Different types of placentation are then discussed, and the various interactions with leukocytes, the extreme being with the equids where a certain degree of 'attack' is often seen. The limits of animal models when dealing with the human situation are emphasized. It is then stated why the various phases of pregnancy are different, and an analysis made of the cellular movements at the implantation, peri-implantation, immediate post-implantation and resorption windows in rodents. Details of the cellular components involved are given, as are hints for the human situation. The Th1/Th2 paradigm is described, with clinical examples, and its limits. Thus, the newly appraised dual role of natural killer (NK) cells is discussed, with examples in rodents and in humans (pre-eclampsia, implantation failure, abortion systems). Clinical data on the IL-12/IL-18/NK tripod and implantation failure in humans are detailed.