Evaluation of KIR genes in recurrent miscarriage

Recurrent Abortion and the Involvement of Killer-Cell Immunoglobulin-like Receptor (KIR) Genes, Activated T Cells, NK Abnormalities, and Cytokine Profiles

Immune tolerance at the feto-maternal interface is crucial for the growth of the semi-allograft fetus in the womb. The outcome of pregnancy is dependent on a fine balance between various immunological forces. For a long time, the potential role of the immune system in pregnancy disorders has remained enigmatic. Current evidence has revealed that natural killer (NK) cells are the predominant immune cell population in the uterine decidua. NK cells cooperate with T-cells to provide an optimal microenvironment for the growth of the developing fetus by producing cytokines, chemokines, and angiogenic factors. These factors support trophoblast migration and angiogenesis which regulates the process of placentation. NK cells differentiate between "self" and "non-self" through their surface receptors known as killer-cell immunoglobulin-like receptors (KIRs). They induce immune tolerance through communication via their KIR and fetal human leucocyte antigens (HLA). KIRs are surface receptors of NKs that comprise both activating and inhibiting receptors. Due to the wide diversity manifested by its genes, the KIR repertoire is different in each individual. Significant evidence has implicated KIRs in recurrent spontaneous abortion (RSA); however, maternal KIR gene diversity in RSA is still unclear. Research has shown that immunological aberrancies including activating KIRs, NK abnormalities, and T cell downregulation are risk factors for RSA. In this review, we discuss relevant data from experimental studies on NK cell abnormalities, KIR, and T-cells in the incidence of recurrent spontaneous abortion.

KIR- Ligand Interactions in Hypertensive Disorders in Pregnancy

Hypothesis

The activity of natural killer (NK) cells is considered an important factor for the tolerance of the fetus during pregnancy. The complications of pregnancy, such as hypertensive disorders (HDP), may be therefore associated with this immune compartment.

Methods

The current study included 41 pregnant women diagnosed with HDPs (Gestational Hypertension; GH or Preeclampsia; PE) and 21 healthy women. All the patients were under continuous obstetric care during the pregnancy and labour. The number of mother-child mismatches within killer immunoglobulin-like receptors (KIRs), their ligands [MM], and missing KIR ligands [MSLs] was assessed. KIRs and their ligands were assessed with Next Generation Sequencing (NGS) and Polymerase Chain Reaction Sequence-Specific Oligonucleotide (PCR-SSO) typing. The subsets of NK cells were assessed with multicolor flow cytometry and correlated to the number of MSLs.

Results

The number of MSLs was significantly higher in HDP patients when compared to healthy non-complicated pregnancy patients. Some MSLs, such as those with 2DS2 activating KIR, were present only in HDP patients. The percentage of CD56+CD16-CD94+ NK cells and CD56+CD16-CD279+ NK cells correlated with the number of MSLs with inhibiting KIRs only in healthy patients. In HDP patients, there was a correlation between the percentage of CD56-CD16+CD69+ NK cells and the number of MSLs with inhibiting and activating KIRs. As compared to the healthy group, the percentage of CD56+CD16-CD279+ NK cells and CD56-CD16+CD279+ NK cells were lower in HDP patients. HDP patients were also characterized by a higher percentage of CD56+CD16+perforin+ NK cells than their healthy counterparts.

Conclusions

Patients with HDP were characterized by a higher number of MSLs within the KIRs receptors. It seemed that the number of MSLs in the healthy group was balanced by various receptors, such as CD94 or inhibitory CD279, expressed on NK cells. Conversely, in HDP patients the number of MSLs was associated with the activation detected as the increased level of CD69+ NK cells.

Immunity at maternal-fetal interface: KIR/HLA (Allo)recognition

Both KIR and HLA are the most variable gene families in the human genome. The recognition of the semi-allogeneic embryo-derived trophoblasts by maternal decidual NK (dNK) cells is essential for the establishment of the functional placenta. This recognition is based on the KIR-HLA interactions and trophoblast expresses a specific HLA profile that constitutes classical polymorphic HLA-C and non-classical oligomorphic HLA-E, HLA-F, and HLA-G molecules. This review highlights some features of the KIR/HLA-C (allo)recognition by decidual NK (dNK) cells as a main immune cell population specifically enriched at maternal-fetal interface during human early pregnancy. How KIR/HLA-C axis operates in pregnancy disorders and in the context of transplacental infections is discussed as well. We summarized old and new data on dNK-cell functional plasticity, their selective expression of KIR and fetal maternal/paternal HLA-C haplotypes present. Results showed that KIR-HLA-C combinations and the corresponding axis operate differently in each pregnancy, determined by the variability of both maternal KIR haplotypes and fetus' maternal/paternal HLA-C allotype combinations. Moreover, the maturation of NK cells strongly depends on if or not HLA allotypes for certain KIR are present. We suggest that the unique KIR/HLA combinations reached in each pregnancy (normal and pathological) should be studied according to well-defined guidelines and unified methodologies to have comparable results ease to interpret and use in clinics.

Significance of inhibitory maternal killer-cell immunoglobulin-like receptor (KIR) and fetal KIR ligand genotype combinations in placenta related obstetric complications

Some maternal killer-cell immunoglobulin-like receptor (KIR) and fetal KIR ligand genotypes are associated with obstetric complications, such as recurrent miscarriage, fetal growth restriction, preeclampsia, and preterm birth. However, how KIR/KIR ligand genotypes affect these placenta-related obstetric complications has not been fully understood. We aimed to demonstrate the association of maternal KIR-fetal KIR ligand genotype combinations with immunological/metabolic risk factor associated placenta-related obstetric complications. This study consisted of three groups of pregnant women: 1) Miscarriage group (n = 30), 2) Complicated Pregnancy (CP) group (n = 30), and 3) Control group (n = 30). The observed maternal genotype frequencies of all inhibitory and activating KIRs were similar in all groups (p > 0.05). However, inhibitory 2DL3 was quite frequent in the miscarriage group (p = 0.052). There was no difference between groups in terms of centromeric and telomeric maternal haplotypes (p > 0.05). The fetal group 1 HLA-C genotype was frequently detected in the miscarriage and CP groups with rates of 83.3 % and 93.3 % respectively, while the observed frequency was 70 % in the control group. The fetal group 2 HLA-C genotype was the same in all groups. The results demonstrated significantly less fetal group 2 HLA-C homozygosity in the CP groups when compared to the control group (p = 0.020). The fetal HLA-Bw4 genotype was detected more frequently in the miscarriage and CP groups (p = 0.028 and p = 0.001, respectively). The inhibitory KIR/KIR ligand genotype combinations of 2DL3-C1 and 3DL1-Bw4 were more frequent in the miscarriage and CP groups (p = 0.045 and p = 0.002, respectively). Enhanced NK cell inhibition may be one of the mechanisms underlying placenta-related obstetric complications.

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.

KIR2DL2/S2 and KIR2DS5 in alcoholic cirrhotic patients undergoing liver transplantation

INTRODUCTION

The molecular mechanisms underlying alcoholic liver fibrosis and cirrhosis are not completely understood. Hepatic fibrosis involves the interplay of diverse cells and factors, including hepatic stellate cells (HSCs), Kupffer, NK cells, and T-lymphocyte subsets. Killer-cell immunoglobulin-like receptors (KIR) are membrane receptors involved in mediation between NK and activated HSCs, regulating NK cell function through their interaction with HLA-I molecules. The aim of this study was to analyse the genetic association between KIR genes and the susceptibility to or protection from alcoholic cirrhosis (AC) in a cohort of male AC patients undergoing liver transplantation (LT) with and without concomitant viral infections.

MATERIAL AND METHODS

KIR genotyping was performed in nuclear DNA extracted from 281 AC patients and compared with 319 male controls.

RESULTS

Significant differences between total AC patients and healthy controls were only found in the case of KIR2DL2 and KIR2DS5. KIR2DL2 was significantly underrepresented in non-viral AC patients (52.6% vs. 63.3%; p = 0.015), while patients heterozygous for KIR2DL2 were also underrepresented in the non-viral AC group compared with controls (p = 0.034). KIR2DS5 was overrepresented in this group compared with healthy controls (p = 0.002). All these observations were only evident in AC patients older than 54 years old.

CONCLUSIONS

Our data suggest a contrary effect of KIR2DL2 and KIR2DS5 in AC patients older than 54 years, in whom the presence of KIR2DL2 appears to be protective against AC, whereas the presence of KIR2DS5 seems to promote the fibrotic process, particularly in patients with no associated viral infection.

Association of Killer Immunoglobulin-Like Receptor and Human Leukocyte Antigen Class I Ligand with Recurrent Abortion in Saudi Women

Aims: This study was designed to determine whether genetic polymorphisms of the killer immunoglobulin-like receptor (KIR) and human leukocyte antigen class I (HLA-C) genes are associated with recurrent spontaneous abortion (RSA) in Saudi women. Materials and Methods: Sixty-five healthy women with a history of RSA (three or more spontaneous abortions) and 65 healthy controls (with two or more healthy-born children) living in Riyadh were typed for 17 KIR genes and the HLA-C1 and HLA-C2 allotypes using polymerase chain reaction-sequence-specific primer methodology. Results: The frequencies of KIR2DS2 and KIR2DL5A were significantly lower among RSA women compared to healthy controls (odds ratio [OR] = 0.17; p < 0.001; OR = 0.16; p < 0.001, respectively). No association with maternal HLA-C genotypes was observed. Analysis of KIR-HLA-C combinations indicated a protective effect of KIR2DS2 with its cognate HLA-C1 ligand in both homozygote or heterozygote combinations. Conclusion: Our results demonstrate that the KIR genes of the B haplotype may play an important role in ensuring the success of pregnancy.

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.

Recurrent Spontaneous Abortion (RSA) and Maternal KIR Genes: A Comprehensive Meta-Analysis

Natural killer cells (NKs) are the most important cells in the fetomaternal immune tolerance induced through interaction of maternal killer-cell immunoglobulin-like receptors (KIR) and fetal human leucocyte antigens (HLA). Hence, we intend to perform a meta-analysis on the role of maternal KIR genes diversity in recurrent spontaneous abortion (RSA). The present paper is a meta-analysis of previous genetic association studies and our previous original study. The results showed that KIR3DL1 was a significantly protecting factor for RSA (p=0.044; OR=0.833 [0.698-0.995]; fixed effect model). KIR2DS2 (p=0.034; OR=1.195 [1.013-1.408]; fixed effect model) and KIR2DS3 (p=0.013; OR=1.246 [1.047-1.483]; fixed effect model) were significantly risk factors for RSA. For KIR2DS1 there was a high heterogeneity and publication bias. Briefly, the inhibitory gene KIR3DL1 was a protecting factor, and the activating genes KIR2DS2 and KIR2DS3 were risk factors for RSA. However, the effect sizes were not suitable. We suggest further studies on different causes of pregnancy loss, to find the role of KIR2DS1.

Genomic Analysis of Spontaneous Abortion in Holstein Heifers and Primiparous Cows

Background: The objectives of this study were to identify loci, positional candidate genes, gene-sets, and pathways associated with spontaneous abortion (SA) in cattle and compare these results with previous human SA studies to determine if cattle are a good SA model for humans. Pregnancy was determined at gestation day 35 for Holstein heifers and cows. Genotypes from 43,984 SNPs of 499 pregnant heifers and 498 pregnant cows that calved at full term (FT) were compared to 62 heifers and 28 cows experiencing SA. A genome-wide association analysis, gene-set enrichment analysis–single nucleotide polymorphism, and ingenuity pathway analysis were used to identify regions, pathways, and master regulators associated with SA in heifers, cows, and a combined population. Results: Twenty-three loci and 21 positional candidate genes were associated (p < 1 × 10⁻⁵) with SA and one of these (KIR3DS1) has been associated with SA in humans. Eight gene-sets (NES > 3.0) were enriched in SA and one was previously reported as enriched in human SA. Four master regulators (p < 0.01) were associated with SA within two populations. Conclusions: One locus associated with SA was validated and 39 positional candidate and leading-edge genes and 2 gene-sets were enriched in SA in cattle and in humans.

Understanding the role of killer cell immunoglobulin-like receptors in pregnancy complications

Pregnancy is a unique immunological situation in which a fetus-bearing paternal histocompatibility antigens can survive in a maternal environment without apparent rejection. To face this challenge, cells of the uterine immune system show characteristic changes in absolute number and composition during pregnancy. Particularly relevant to this process are uterine natural killer (uNK) cells and their cell surface receptors, killer immunoglobulin-like receptors (KIRs). The main purpose of this review is to outline the current body of knowledge on the involvement of KIRs in the complications of pregnancy. Implantation depends on the invasion of embryonic trophoblast cells into maternal uterine tissue and remodeling of the uterine spiral arterioles, which is essential for placental perfusion and successful pregnancy. The proper interaction between maternal KIRs and their ligands human leukocyte antigen (HLA) class I molecules, expressed by the extravillous trophoblast cells, is crucial in this process. KIRs are a complex family that includes both activator and inhibitory receptors. The activation profile is genetically determined in each individual and leads to diverse levels of functionality for NK and T cells on engagement with specific HLA class I molecules. An association between different KIR alleles and HLA molecules has been reported in pregnancy complications, supporting the idea of a relevant role of these receptors in successful pregnancy.

Regulation and Function of NK and T Cells During Dengue Virus Infection and Vaccination

The focus of this review is to discuss findings in the last 10 years that have advanced our understanding of human NK cell responses to dengue virus. We will review recently identified interactions of activating and inhibitory receptors on NK cells with dengue virus, human NK responses to natural dengue infection and highlight possible interactions by which NK cells may shape adaptive immune responses. T cell responses to natural dengue infection will be reviewed by Laura Rivino in Chap. 17 . With the advent of numerous dengue vaccine clinical trials, we will also review T and NK cell immune responses to dengue virus vaccination. As our understanding of the diverse functions of NK cell has advanced, it has become increasingly clear that human NK cell responses to viral infections are more complicated than initially recognized.

Maternal natural killer cell immunoglobulin receptor genes and human leukocyte antigen-C ligands influence recurrent spontaneous abortion in the Han Chinese population

The underlying mechanism of recurrent spontaneous abortion (RSA) has remained elusive for many years. Several previous studies have suggested that the killer cell immunoglobulin receptor (KIR) gene family is associated with RSA, however, it is not clear exactly how. The present study detected KIR and human leukocyte antigen-C (HLA-C) genes in 110 Han Chinese women with unexplained RSA and 105 Han Chinese healthy females. The aim of the present study was to determine if certain genotypes were more susceptible to the occurrence of miscarriage. The frequency of KIR genes and different KIR haplotypes in the 2 groups demonstrated no statistical differences. However, in women who had miscarried ≥3 times, the frequency of KIR3DL1 was significantly reduced and the BB haplotype frequency was significantly higher compared with the control group. HLA-C2C2 was significantly increased in the KIR AB and KIR BB groups in the RSA groups compared with the control group. The women in the RSA group who had a homozygous HLA-C2C2 had a significantly higher frequency of the 2DS1 gene compared with the control group. The reduction of inhibitory gene and increased activation combinations may induce the activation of uterine natural killer cells, which may reduce the probability of fetal survival. To the best of our knowledge, the present study is the first report demonstrating the association between maternal KIR and HLA-C genes and RSA in women of a Han Chinese ethnicity. The present study revealed that females who miscarry ≥3 times may be used as selection criteria for RSA and so may exhibit higher research value.

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 role of KIR and HLA interactions in pregnancy complications

Combinations of KIR and HLA genes associate with pregnancy complications as well as with many other clinical scenarios. Understanding how certain KIR and HLA genes influence the biology of a disease is, however, a formidable challenge. These are the two most variable gene families in the human genome. Moreover, the biology of a disease is best understood by studying the cells of the affected tissue. Natural Killer (NK) cells express KIR and are the most abundant leukocytes in the uterus. Most of our knowledge of NK cells is based on what we have learned from cells isolated from blood, but these are different from their tissue resident counterparts, including uterine NK (uNK) cells. Reproductive immunology faces an additional challenge: Two genotypes must be considered because both maternal and foetal HLA class I molecules may influence the outcome of pregnancy, most likely through interactions with maternal KIR expressed on uNK cells. Maternal uNK cells are not spontaneously cytotoxic and instead engage in interactions with trophoblast. We hypothesise that these interactions regulate allocation of resources between the foetus and the mother and may go wrong in diseases of pregnancy.

Identification of minor chromosomal defects causing abnormal foetus and spontaneous abortions

BACKGROUND

Chromosomal abnormalities are the most common cause of recurrent abortions and miscarriages (RAM), but micro-variations on chromosomes causing RAM have never been previously studied. Single nucleotide polymorphisms (SNPs) are the single nucleotide variations frequently present at genome with the density of at least one common (>20% allele frequency) SNP per kilobase pair. It has already been reported that SNP array examination for chromosomal abnormalities has better performance than the conventional cytogenetic karyotyping.

METHODS

We applied SNP array to detect the chromosomal defects in 80 placental villi and foetal tissues of abnormal foetus and spontaneous abortions.

RESULTS

The analyses of data revealed that total 52.5% (42/80) cases were found to have chromosomal abnormalities. The trisomies were most commonly found 26/42 (61.9%) in current samples. Total 8/42 (19.1%) cases were found to have other structural aberrations including translocations in 2/8 (25%), duplications and deletions in 3/8 (37.5%) cases, respectively. SNP analysis also successfully detected triploidy 69,XXX and tetraploidy 92,XXXY. Total 12/80 cases were performed by cytogenetic karyotyping and results were compared with SNP data. Total 5/12 (41.7%) cases were found to have same findings with SNP data while results of 2/12 (16.7%) cases had partial similarity between both techniques. Four cases were declared as karyotypically normal (46,XY or 46,XX) by cytogenetic examination, but later on these four cases were found to have small chromosomal variation which could be the cause of RAM in women.

CONCLUSION

Therefore, we conclude that use of a high-density SNP platform in diagnosis can give better understanding of molecular causes of pregnancy loss and foetal abnormalities.

Possible Role of HLA-G, LILRB1 and KIR2DL4 Gene Polymorphisms in Spontaneous Miscarriage

The KIR2DL4 receptor and its ligand HLA-G are considered important for fetal-maternal immune tolerance and successful pregnancy. The absence of a particular variant of KIR2DL4 might be a bad prognostic factor for pregnancy outcome. However, it could be compensated by the presence of the respective LILRB1 allele. Therefore, we investigated the KIR2DL4, LILRB1 and HLA-G polymorphisms in 277 couples with spontaneous abortion and 219 control couples by HRM, PCR-SSP and RFLP methods. We found a protective effect of women’s heterozygosity in −716 HLA-G (p = 0.0206) and LILRB1 (p = 0.0131) against spontaneous abortion. Surprisingly, we observed more 9A/10A genotypes of KIR2DL4 gene carriers in the group of male partners from the miscarriage group in comparison to the men from the control group (p = 0.0288). Furthermore, there was no association of women’s KIR2DL4 polymorphism with susceptibility to spontaneous abortion. Multivariate analysis indicated that women’s −716 HLA-G and LILRB1 and men’s KIR2DL4 9A/10A are important in terms of the protection or susceptibility to miscarriage, respectively (p = 0.00968). In conclusion, a woman’s heterozygosity in HLA-G and LILRB1 might be an advantage for a success of reproduction, but the partner’s heterozygosity in 9A/10A KIR2DL4 alleles might not.

Recurrent Pregnancy Loss in Women with Killer Cell Immunoglobulin-Like Receptor KIR2DS1 is Associated with an Increased HLA-C2 Allelic Frequency

PROBLEM

During human pregnancy, the uterine lining is highly populated with killer-immunoglobulin-like receptor (KIR)-expressing NK cells that recognize HLA-C molecules on trophoblast cells. The goal of this study was to analyze the KIR gene contents and frequencies in a N. American cohort of women with RPL of unknown etiology to evaluate whether there is a genetic susceptibility to RPL based on a woman's KIR repertoire and her HLA-C group, as well as the HLA-C group of the partner.

METHOD OF STUDY

The frequencies of KIR and HLA-C1 and HLA-C2 genes were evaluated in 139 Caucasian women with RPL; HLA-C1, and HLA-C2 group genes were analyzed in their partners (n = 42). The gene frequencies were compared with data reported from corresponding populations.

RESULTS

Overall, the frequencies of HLA-C groups and KIR genes and genotypes in RPL cohort resembled the frequencies for US Caucasians. The HLA-C1 and HLA-C2 group distribution was significantly different between women with or without KIR2DS1. Women positive for KIR2DS1 (45.3% of the study cohort) had an increased frequency of its ligand, HLA-C2 (0.5159 versus 0.3684 in KIR2DS1 negative women, P = 0.014).

CONCLUSION

Our results indicate that among KIR2DS1 pos women, the co-expression of HLA-C2 is associated with RPL.

Hepatitis C Virus Sensing by Human Trophoblasts Induces Innate Immune Responses and Recruitment of Maternal NK Cells: Potential Implications for Limiting Vertical Transmission

Hepatitis C virus (HCV) is the world's most common blood-borne viral infection for which there is no vaccine. The rates of vertical transmission range between 3 and 6% with odds 90% higher in the presence of HIV coinfection. Prevention of vertical transmission is not possible because of lack of an approved therapy for use in pregnancy or an effective vaccine. Recently, HCV has been identified as an independent risk factor for preterm delivery, perinatal mortality, and other complications. In this study, we characterized the immune responses that contribute to the control of viral infection at the maternal-fetal interface (MFI) in the early gestational stages. In this study, we show that primary human trophoblast cells and an extravillous trophoblast cell line (HTR8), from first and second trimester of pregnancy, express receptors relevant for HCV binding/entry and are permissive for HCV uptake. We found that HCV-RNA sensing by human trophoblast cells induces robust upregulation of type I/III IFNs and secretion of multiple chemokines that elicit recruitment and activation of decidual NK cells. Furthermore, we observed that HCV-RNA transfection induces a proapoptotic response within HTR8 that could affect the morphology of the placenta. To our knowledge, for the first time, we demonstrate that HCV-RNA sensing by human trophoblast cells elicits a strong antiviral response that alters the recruitment and activation of innate immune cells at the MFI. This work provides a paradigm shift in our understanding of HCV-specific immunity at the MFI as well as novel insights into mechanisms that limit vertical transmission but may paradoxically lead to virus-related pregnancy complications.

Future directions of clinical laboratory evaluation of pregnancy

In recent years, our understanding of how the immune system interacts with the developing fetus and placenta has greatly expanded. There are many laboratories that provide tests for diagnosis of pregnancy outcome in women who have recurrent pregnancy loss (RPL) or pre-eclampsia. These tests are based on the premise that immune response to the fetus is equivalent to the adaptive immune response to a transplant. New understanding leads to the concept that the activated innate response is vital for pregnancy and this can result in more effective testing and treatment to prevent an abnormal pregnancy in the future. We describe here only three such areas for future testing: one area involves sperm and semen and factors necessary for successful fertilization; another area would determine conditions for production of growth factors necessary for implantation in the uterus; finally, the last area would be to determine conditions necessary for the vascularization of the placenta and growing fetus by activated natural killer (NK) cells (combinations of killer cell immunoglobulin-like receptor (KIR) family genes with HLA-C haplotypes) that lead to capability of secreting angiogenic growth factors. These areas are novel but understanding their role in pregnancy can lead to insight into how to maintain and treat pregnancies with complicating factors.

Trophoblasts and decidual stromal cells regulate decidual NK cell functions via interaction between collagen and LAIR-1

PROBLEM

To determine the effect of collagen from maternal-fetal interface on decidual natural killer cell (dNK) function.

METHOD OF STUDY

Decidual and villous samples were collected from normal pregnancy and miscarriage. The phenotype and cytokine production were analyzed, respectively, by flow cytometry and enzyme-linked immunosorbent assay (ELISA). Co-culture was established to investigate the effect of trophoblasts and decidual stromal cells (DSCs) on dNKs.

RESULTS

Maternal-fetal interface of normal pregnancy showed higher collagen and LAIR-1 expression than that of miscarriage. Co-culture of dNKs with HTR-8/DSCs up-regulated LAIR-1 on dNKs that could be attenuated by pre-treatment with LAIR-2, a competitive inhibitor of LAIR-1. Collagen down-regulated expression of cell surface receptor activity and intracellular perforin, while it up-regulated expression of suppressive receptor on dNKs. Co-culture of dNKs with HTR-8/DSCs decreased perforin expression and Th1-type cytokines production by dNKs, which could be abrogated by LAIR-2. In addition, silence of collagen in HTR-8/DSCs by shRNA significantly attenuated regulation on dNKs.

CONCLUSION

Trophoblasts and DSCs regulate decidual NK cell functions via secreting collagen, which is involved in the maintenance of human pregnancy.

NK cells in immunotolerant organs

Organs such as the liver, uterus and lung possess hallmark immunotolerant features, making these organs important for sustaining self-homeostasis. These organs contain a relatively large amount of negative regulatory immune cells, which are believed to take part in the regulation of immune responses. Because natural killer cells constitute a large proportion of all lymphocytes in these organs, increasing attention has been given to the roles that these cells play in maintaining immunotolerance. Here, we review the distribution, differentiation, phenotypic features and functional features of natural killer cells in these immunotolerant organs, in addition to the influence of local microenvironments on these cells and how these factors contribute to organ-specific diseases.

Killer cell immunoglobulin-like receptor gene associations with autoimmune and allergic diseases, recurrent spontaneous abortion, and neoplasms

Killer cell immunoglobulin-like receptors (KIRs) are a family of cell surface inhibitory or activating receptors expressed on natural killer cells and some subpopulations of T lymphocytes. KIR genes are clustered in the 19q13.4 region and are characterized by both allelic (high numbers of variants) and haplotypic (different numbers of genes for inhibitory and activating receptors on individual chromosomes) polymorphism. This contributes to diverse susceptibility to diseases and other clinical situations. Associations of KIR genes, as well as of genes for their ligands, with selected diseases such as psoriasis vulgaris and atopic dermatitis, rheumatoid arthritis, recurrent spontaneous abortion, and non-small cell lung cancer are discussed in the context of NK and T cell functions.