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

Association of parental HLA-G polymorphisms with soluble HLA-G expressions and their roles on recurrent implantation failure: A systematic review and meta-analysis

Introduction

HLA-G plays a central role in immune tolerance at the maternal-fetal interface. The HLA-G gene is characterized by low allelic polymorphism and restricted tissue expression compared with classical HLA genes. HLA-G polymorphism is associated with HLA-G expression and linked to pregnancy complications. However, the association of parental HLA-G polymorphisms with soluble HLA-G (sHLA-G) expression and their roles in recurrent implantation failure (RIF) is unclear. The study aims to systematically review the association of HLA-G polymorphisms with RIF, the association of sHLA-G expression with RIF, and the association of HLA-G polymorphisms with sHLA-G expressions in patients attending in-vitro fertilization (IVF) treatment.

Methods

Studies that evaluated the association of HLA-G polymorphisms with RIF, the association between sHLA-G expression with RIF, and the association between HLA-G polymorphisms with sHLA-G expressions in patients attending IVF treatment were included. Meta-analysis was performed by random-effect models. Sensitivity analysis was performed by excluding one study each time. Subgroup analysis was performed based on ethnicity.

Results

HLA-G 14bp ins variant is associated with a lower expression of sHLA-G in seminal or blood plasma of couples attending IVF treatment. The maternal HLA-G*010101 and paternal HLA-G*010102 alleles are associated with RIF risk compared to other alleles. However, single maternal HLA-G 14bp ins/del polymorphism, HLA-G -725 C>G/T polymorphism, or circulating sHLA-G concentration was not significantly associated with RIF in the general population. HLA-G 14bp ins/ins homozygous genotype or ins variant was associated with a higher risk of RIF in the Caucasian population.

Discussion

Specific HLA-G alleles or HLA-G polymorphisms are associated with sHLA-G expression in couples attending IVF treatment. Several HLA-G polymorphisms may be related to RIF, considering different ethnic backgrounds. A combined genetic effect should be considered in future studies to confirm the association of HLA-G polymorphisms and sHLA-G expressions in relation to RIF.

Epigenetic and transcriptomic reprogramming in monocytes of severe COVID-19 patients reflects alterations in myeloid differentiation and the influence of inflammatory cytokines

BACKGROUND

COVID-19 manifests with a wide spectrum of clinical phenotypes, ranging from asymptomatic and mild to severe and critical. Severe and critical COVID-19 patients are characterized by marked changes in the myeloid compartment, especially monocytes. However, little is known about the epigenetic alterations that occur in these cells during hyperinflammatory responses in severe COVID-19 patients.

METHODS

In this study, we obtained the DNA methylome and transcriptome of peripheral blood monocytes from severe COVID-19 patients. DNA samples extracted from CD14 + CD15- monocytes of 48 severe COVID-19 patients and 11 healthy controls were hybridized on MethylationEPIC BeadChip arrays. In parallel, single-cell transcriptomics of 10 severe COVID-19 patients were generated. CellPhoneDB was used to infer changes in the crosstalk between monocytes and other immune cell types.

RESULTS

We observed DNA methylation changes in CpG sites associated with interferon-related genes and genes associated with antigen presentation, concordant with gene expression changes. These changes significantly overlapped with those occurring in bacterial sepsis, although specific DNA methylation alterations in genes specific to viral infection were also identified. We also found these alterations to comprise some of the DNA methylation changes occurring during myeloid differentiation and under the influence of inflammatory cytokines. A progression of DNA methylation alterations in relation to the Sequential Organ Failure Assessment (SOFA) score was found to be related to interferon-related genes and T-helper 1 cell cytokine production. CellPhoneDB analysis of the single-cell transcriptomes of other immune cell types suggested the existence of altered crosstalk between monocytes and other cell types like NK cells and regulatory T cells.

CONCLUSION

Our findings show the occurrence of an epigenetic and transcriptional reprogramming of peripheral blood monocytes, which could be associated with the release of aberrant immature monocytes, increased systemic levels of pro-inflammatory cytokines, and changes in immune cell crosstalk in these patients.

Role of polymorphisms on the Recurrent Pregnancy Loss: A systematic review, Meta-analysis and bioinformatic analysis

Recurrent miscarriage (RM) is a major reproductive health issue. RM is a multi-factorial disease, and is affected by environmental, genetic, and epigenetic factors. Genetics has a common role in recurrent miscarriage occurrence. It seems that molecular genetics has a great role in RSA incidence. So, in these years, RM has become for a major subject of genetics research. There are many genes that are involved in each phase for successful reproduction. This research aimed to evaluate the effect of all studied polymorphisms in studies on RSA that have not been included in any meta-analysis. PubMed, Scopus, and Web of Science databases were recruited to investigate the related articles. The systematic review results identified 143 studies worldwide. Thirteen genes have been included in assessing the case-control studies. Sixty-four SNPs were recruited to assess the association between genetic factors and RSA susceptibility. Ninety-two studies containing twenty two SNPs (from 10 genes) were included in the quantitative analysis. Bioinformatic analysis indicated that rs12722482 showed "Damaging Status" by double servers, and rs315952 and rs854560 had "Possibly damaging" status in the PolyPhen-2 server. MethPrimer server indicated that there is "CpG Island" in the rs10895068, rs1130355, and rs41557518 variants, and rs10895068-G allele makes a CpG dinucleotide which can change the gene methylation and result in altering the gene expression. So, further studies on rs12722482 and rs10895068 can demonstrate valuable results. To the best of our knowledge, this systematic review has covered the all studied polymorphisms of HLA-C, HLA-G, PON1, AGTR1, TAFI, FAS, FAS-L, ESR1, PGR, CTLA-4, MMP-2, MMP-3, MMP-9, and IL1RN for the first time. Also, we did a novel meta-analysis for AGTR1 rs5186, TAFI rs1926447, rs3742264, HLA-G rs1063320, rs1233334, rs1736936, rs2249863, PON1 rs662, rs854560, FAS rs2234767, rs1800682, FAS-L rs763110, ESR1, rs9340799, rs3798759, PGR rs1042838, CTLA4 rs4553808, rs5742909, rs231775, rs3087243, and MMP-2 rs243865 and updated statistical finding for rs2234693 and rs371194629. Rs2234693, rs9340799, rs231775, and rs371194629 demonstrated a significant association with RSA risk. Some variations showed significant association, while further studies are suggested to confirm the results. Finally, Rs4553808 and rs5742909 revealed no significant deviation in the results. It is suggested that these SNPs may be excluded from subsequent case-control studies or other analyses.

KIR2DL4 genetic diversity in a Brazilian population sample: implications for transcription regulation and protein diversity in samples with different ancestry backgrounds

KIR2DL4 is an important immune modulator expressed in natural killer cells; HLA-G is its main ligand. We have characterized the KIR2DL4 genetic diversity by considering the promoter, all exons, and all introns in a highly admixed Brazilian population sample and by using massively parallel sequencing. We introduce a molecular method to amplify and to sequence the complete KIR2DL4 gene. To avoid the mapping bias and genotype errors commonly observed in gene families, we have developed and validated a bioinformatic pipeline designed to minimize these errors and applied it to survey the variability of 220 individuals from the State of São Paulo, southeastern Brazil. We have also compared the KIR2DL4 genetic diversity in the Brazilian cohort with the diversity previously reported by the 1000Genomes consortium. KIR2DL4 presents high linkage disequilibrium throughout the gene, with coding sequences associated with specific promoters. There are few but divergent promoter haplotypes. We have also detected many new KIR2DL4 sequences, all bearing nucleotide exchanges in introns and encoding previously described proteins. Exons 3 and 4, which encode the external domains, are the most variable. The ancestry background influences the KIR2DL4 allele frequencies and must be considered for association studies regarding KIR2DL4.

Roles of HLA-G in the Maternal-Fetal Immune Microenvironment

During pregnancy, the maternal uterus and fetus form a special microenvironment at the maternal-fetal interface to support fetal development. Extravillous trophoblasts (EVTs), differentiated from the fetus, invade into the decidua and interact with maternal cells. Human leukocyte antigen (HLA)-G is a non-classical MHC-I molecule that is expressed abundantly and specifically on EVTs in physiological conditions. Soluble HLA-G (sHLA-G) is also found in maternal blood, amniotic fluid, and cord blood. The abnormal expression and polymorphisms of HLA-G are related to adverse pregnancy outcomes such as preeclampsia (PE) and recurrent spontaneous abortion (RSA). Here we summarize current findings about three main roles of HLA-G during pregnancy, namely its promotion of spiral artery remodeling, immune tolerance, and fetal growth, all resulting from its interaction with immune cells. These findings are not only of great significance for the treatment of pregnancy-related diseases but also provide clues to tumor immunology research since HLA-G functions as a checkpoint in tumors.

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.

Association of Soluble HLA-G Plasma Level and HLA-G Genetic Polymorphism With Pregnancy Outcome of Patients Undergoing in vitro Fertilization Embryo Transfer

Infertility is currently a growing problem observed around the world and is estimated to affect between 8 and 12% of reproductive-aged couples worldwide. Artificial reproductive techniques are the last chance for couples seeking their own child. Human leukocyte antigen (HLA)-G expression has been suggested as an immunomodulatory molecule that influences pregnancy outcome. The HLA-G gene encodes either membrane-bound or/and soluble proteins. The aim of this study was the evaluation of the role of soluble HLA-G (sHLA-G) and its gene polymorphism in successful implantation after in vitro fertilization embryo transfers (IVF-ETs) in different clinical protocols. We tested the HLA-G polymorphism in three positions: rs1632947: c.-964G>A; rs1233334: c.-725G>C/T in promoter region; rs371194629: c.^*65_^*66insATTTGTTCATGCCT in 3′ untranslated region of exon 8, in 389 patients who underwent IVF-ETs and 320 women with healthy children born after natural conception. Among the patient group, 239 women were with recurrent implantation failure and 117 women had an ongoing pregnancy or a child born after IVF-ET. We found that certain rs1632947-rs1233334-rs371194629 HLA-G haplotypes and diplotypes were associated with infertility, while others were protective. The lowest secretors of sHLA-G were G-C-ins haplotype carriers (37.21 IU/ml), while the highest -G-C-del carriers (73.80 IU/ml). Other haplotype carriers were intermediate secretors. In our study, regardless of possessed haplotype by the patient, 59.73 IU/ml sHLA-G was the threshold value with the best sensitivity (58.82%) and specificity (66.10%) to discriminate patients who achieved and maintained pregnancy from those who did not conceive or they had miscarriage (p = 0.0085; likelihood ratio, 1.74; 95% CI = 0.55–0.78). However, we do not exclude that factors other than sHLA-G may also contribute to complications in pregnancy. In addition, we found that IVF patients in cycles when frozen/thawed embryo was transferred secreted higher soluble HLA-G levels than patients with fresh embryo transferred (p = 0.021). Moreover, correlation analysis of sHLA-G concentration measured before and after embryo transfer for particular patients indicated short ovarian stimulation with gonadotropin-releasing hormone antagonist as more beneficial than long protocol with gonadotropin-releasing hormone agonist. Our study confirms a role of HLA-G polymorphism in infertility and soluble HLA-G in the early stages of pregnancy.

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.

Towards a gamete matching platform: using immunogenetics and artificial intelligence to predict recurrent miscarriage

The degree of Allele sharing of the Human Leukocyte Antigen (HLA) genes has been linked with recurrent miscarriage (RM). However, no clear genetic markers of RM have yet been identified, possibly because of the complexity of interactions between paternal and maternal genes during embryo development. We propose a methodology to analyse HLA haplotypes from couples either with histories of successful pregnancies or RM. This article describes a method of RM genetic-risk calculation. The proposed HLA representation techniques allowed us to create an algorithm (IMMATCH) to retrospectively predict RM with an AUC = 0.71 (p = 0.0035) thanks to high-resolution typing and the use of linear algebra on peptide binding affinity data. The algorithm features an adjustable threshold to increase either sensitivity or specificity, allowing a sensitivity of 86%. Combining immunogenetics with artificial intelligence could create personalised tools to better understand the genetic causes of unexplained infertility and a gamete matching platform that could increase pregnancy success rates.

Genetic association between HLA-G 14-bp polymorphism and diseases: A systematic review and meta-analysis

BACKGROUND

HLA-G is an immune checkpoint molecule. Since a differential molecule expression has been reported even for healthy individuals, many studies have focused on polymorphisms at HLA-G regulatory regions, particularly the 3' untranslated region (3'UTR). The presence/absence of a 14-bp sequence was the first polymorphism described and it is the most studied in association between HLA-G and disorders.

METHODS

In this study, we performed a systematic review and meta-analysis of all association studies published regarding the HLA-G 14-bp.

RESULTS

We verified association between 14-bp alleles and diseases in the following situations: (1) presence of 14-bp (insertion) conferred susceptibility to preeclampsia (child alleles evaluated) and systemic lupus erythematosus (OR = 1.42; 95%CI = 1.04-1.93; p = 0.026 and OR = 1.13; 95%CI = 1.01-1.27, p = 0.028); (2) 14-bp absence (deletion) was associated with increased risk to breast cancer (OR = 1.23; 95%CI = 1.06-1.43; p = 0.006) and human Cytomegalovirus infection (OR = 2.06; 95%CI = 1.60-2.64; p < 0.0001); and (3) a risk association was observed between the group of reproductive disorders and the 14-bp insertion (OR = 1.12; 95%CI = 1.01-1.24; p = 0.034).

CONCLUSIONS

Considering that others 14-bp associations were inconclusive and that other variation sites observed at HLA-G 3'UTR exhibit a proven role on post-transcriptional regulation of HLA-G expression, the complete 3'UTR segment should be analyzed in terms of disease susceptibility, instead of a single polymorphism.

Soluble HLA-G Expression Inversely Correlates With Fetal Microchimerism Levels in Peripheral Blood From Women With Scleroderma

Women with scleroderma (SSc) maintain significantly higher quantities of persisting fetal microchimerism (FMc) from complete or incomplete pregnancies in their peripheral blood compared to healthy women. The non-classical class-I human leukocyte antigen (HLA) molecule HLA-G plays a pivotal role for the implantation and maintenance of pregnancy and has often been investigated in offspring from women with pregnancy complications. However data show that maternal HLA-G polymorphisms as well as maternal soluble HLA-G (sHLA-G) expression could influence pregnancy outcome. Here, we aimed to investigate the underlying role of maternal sHLA-G expression and HLA-G polymorphisms on the persistence of FMc. We measured sHLA-G levels by enzyme linked immunosorbent assay in plasma samples from 88 healthy women and 74 women with SSc. Male Mc was quantified by DYS14 real-time PCR in blood samples from 58 women who had previously given birth to at least one male child. Furthermore, eight HLA-G 5'URR/3'UTR polymorphisms, previously described as influencing HLA-G expression, were performed on DNA samples from 96 healthy women and 106 women with SSc. Peripheral sHLA-G was at lower concentration in plasma from SSc (76.2 ± 48.3 IU/mL) compared to healthy women (117.5 ± 60.1 IU/mL, p < 0.0001), independently of clinical subtypes, autoantibody profiles, disease duration, or treatments. Moreover, sHLA-G levels were inversely correlated to FMc quantities (Spearman correlation, p < 0.01). Finally, women with SSc had lower sHLA-G independently of the eight HLA-G 5'URR/3'UTR polymorphisms, although they were statistically more often homozygous than heterozygous for HLA-G polymorphism genotypes -716 (G/T), -201 (G/A), 14 bp (ins/del), and +3,142 (G/A) than healthy women. In conclusion, women with SSc display less sHLA-G expression independently of the eight HLA-G polymorphisms tested. This decreased production correlates with higher quantities of persisting FMc commonly observed in blood from SSc women. These results shed some lights on the contribution of the maternal HLA-G protein to long-term persistent fetal Mc and initiate new perspectives in this field.

Evaluation of HLA-G 14-bp ins/del and +3142G>C polymorphisms with susceptibility to recurrent spontaneous abortion

OBJECTIVE

HLA-G is critically important for successful implantation during pregnancy. Increasing evidence supposed that HLA-G plays a key role in tolerance of the semi-allogeneic graft in pregnancy by inhibiting the cytotoxic functions of T and NK cells. The present study aimed to evaluate the impact of HLA-G rs1063320 (+3142G>C) and 14-bp insertion (ins)/deletion (del) polymorphisms on recurrent spontaneous abortion (RSA).

MATERIALS AND METHODS

Genomic DNA from 93 RSA patients and 93 normal fertile women was isolated using the salting out method. Genotyping of HLA-G +3142G>C and 14-bp ins/del variants was done by polymerase chain reaction restriction fragment length polymorphism (PCR-RFP) and PCR method, respectively.

RESULTS

The HLA-G +3142G>C polymorphism increased the risk of RSA in codominant (OR = 2.39, 95%CI = 1.27-4.49, p = 0.010, GC vs GG; OR = 3.28, 95%CI = 1.16-9.72, p = 0.040, CC vs GG) and dominant (OR = 2.52, 95%CI = 1.37-4.64, p = 0.004, GC + CC vs GG) tested inheritance models. HLA-G rs1063320 C allele was associated with increased risk of RSA (OR = 1.84, 95%CI = 1.20-2.83, p = 0.007). The del/del genotype as well as del allele of 14-bp ins/del variant increased that risk of RSA (OR = 3.02, 95%CI = 1.23-7.41, p = 0.025 and OR = 1.65, 95%CI = 1.09-2.50, p = 0.022, respectively).

CONCLUSION

In summary, our results showed that HLA-G gene polymorphisms significantly increased the risk of RSA in a sample of the Iranian population.

The impact of HLA-G, LILRB1 and LILRB2 gene polymorphisms on susceptibility to and severity of endometriosis

Endometriosis is a disease in which endometriotic tissue occurs outside the uterus. Its pathogenesis is still unknown. The most widespread hypothesis claims that ectopic endometrium appears as a result of retrograde menstruation and its insufficient elimination by immunocytes. Some reports have shown expression of non-classical HLA-G molecules on ectopic endometrium. HLA-G is recognized by KIR2DL4, LILRB1 and LILRB2 receptors on natural killer (NK) and other cells. These receptors are polymorphic, which may affect their activity. In this study we investigated whether HLA-G, KIR2DL4, LILRB1 and LILRB2 polymorphisms may influence susceptibility to endometriosis and disease progression. We used polymerase chain reaction (PCR), PCR-restriction fragment length polymorphism (PCR-RFLP) and allelic discrimination methods with TaqMan SNP Genotyping Assays for typing of 276 patients with endometriosis and 314 healthy fertile women. The HLA-G rs1632947:GG genotype was associated with protection against the disease and its severe stages; HLA-G rs1233334:CT protected against progression; LILRB1 rs41308748:AA and LILRB2 rs383369:AG predisposed to the disease and its progression. No effect of KIR2DL4 polymorphism was observed. These results support the role of polymorphisms of HLA-G and its receptors LILRB1 and LILRB2 in susceptibility to endometriosis and its progression.

The methylenetetrahydrofolate reductase c.c.677 C>T and c.c.1298 A>C polymorphisms in reproductive failures: Experience from an RSA and RIF study on a Polish population

Almost 1600 individuals from the Polish population were recruited to this study. Among them 319 were fertile couples, 289 were recurrent spontaneous abortion (RSA) couples, and 131 were in the group of recurrent implantation failure (RIF) following in vitro fertilization. The aim of this study was to evaluate the MTHFR c.c.677 C>T and c.c.1298 A>C polymorphisms’ association with RSA and RIF. We used PCR-RFLP with HinfI (677 C>T) and MboII (1298 A>C) digestion. We observed a protective effect of the female AC genotype (OR = 0.64, p = 0.01) and the C allele (AC+CC genotypes; OR = 0.65, p = 0.009) against RSA. Moreover, 1298 AA/677 CT women were more frequent in RSA (31.14%) and RIF (25.20%) groups in comparison to fertile women (22.88%), although this difference was significant only in the case of RSA (p = 0.022, OR = 1.52). Male combined genotype analysis revealed no association with reproductive failure of their partners. Nevertheless, the female/male combination AA/AC of the 1298 polymorphism was more frequent in RSA couples (p = 0.049, OR = 1.49). However, the significant results became insignificant after Bonferroni correction. In addition, analysis of haplotypes showed significantly higher frequency of the C/C haplotype (1298 C/677 C) in the female control group than in the female RSA group (p = 0.03, OR = 0.77). Moreover, the association between elevated homocysteine (Hcy) level in plasma of RSA and RIF women and MTHFR polymorphisms was investigated but did not reveal significant differences. In conclusion, for clinical practice, it is better to check the homocysteine level in plasma and, if the Hcy level is increased, to recommend patients to take folic acid supplements rather than undergo screening of MTHFR for 1298 A>C and 677 C>T polymorphisms.

Antiphospholipid syndrome and recurrent miscarriage: A systematic review and meta-analysis

Antiphospholipid syndrome (APS) is an autoimmune condition that is associated with thrombosis and morbidity in pregnancy. The exact mechanisms by which these associations occur appear to be heterogeneous and are not yet well understood. The aim of this study was to identify and analyze publications in recent years to better understand the diagnosis and its contribution to monitoring APS among women with recurrent miscarriage (RM). This systematic review and meta-analysis was conducted using the PubMed and Web of Knowledge databases, with articles published between 2010 and 2014, according to the PRISMA statement. Of the 85 identified studies, nine were selected. Most of the studies reported an association between recurrent miscarriage and specific antiphospholipid antibodies, as anticardiolipin antibodies (aCL), lupus anticoagulant (LA), anti-β2-glycoprotein I antibodies (aβ2GPI) and antiphosphatidylserine (aPS), which showed a relationship with RM. The main result of the meta-analysis revealed association between antiphospholipid antibodies (aPLs) and/or APS compared to the patients with RM (OR: 0.279; 95% CI: 0.212-0.366) and APS cases compared to the patients with RM (OR: 0.083; 95% CI: 0.036-0.189). High heterogeneity among these studies (I²=100.0%, p <0.001) was observed. In addition, there was no significant publication bias across studies according to Begg's test (p=0.230), although Egger's test (p=0.037) suggests significant publication bias. The funnel plot was slightly asymmetrical. Systematic review and meta-analysis demonstrated a positive association between antiphospholipid antibodies and/or antiphospholipid syndrome in patients with recurrent miscarriage.

KIR, LILRB and their Ligands' Genes as Potential Biomarkers in Recurrent Implantation Failure

Reproductive failure in humans is a very important social and economic problem, because nowadays women decide to conceive later in life and delay motherhood. Unfortunately, with increasing age they have less chance for natural fertilization and maintenance of pregnancy. Many of them need assisted reproductive technology. Approximately 10% of women after in vitro fertilization-embryo transfers experience recurrent implantation failure (RIF). Multiple factors may contribute to RIF, including oocyte and sperm quality, parental chromosomal anomalies, genetic or metabolic abnormalities of the embryo, poor uterine receptivity, immunological disturbances in the implantation site, and some gynecologic pathologies such as endometriosis, uterine fibroids, hydrosalpinx and endometrial polyps. Moreover, the procedure of in vitro fertilization itself could adversely influence the implantation. Nowadays, many studies are focused on the role of natural killer (NK) cells in normal and pathologic pregnancy because NK cells constitute the dominant cell population in the endometrium and they come in close contact with the allogeneic extravillous trophoblast cells in early pregnancy decidua. The majority of these cells are of CD56^bright phenotype. These cells can express killer immunoglobulin-like receptors (KIRs), which, upon recognition of HLA class I molecules (HLA-C and HLA-G) on trophoblasts, may either stimulate or inhibit NK cells to produce soluble factors, and display low cytotoxicity necessary for maintenance of the allogeneic embryo and fetus in the next steps of pregnancy. Moreover, some members of the leukocyte immunoglobulin-like receptor (LILR) family, also named ILT (immunoglobulin-like transcript), are present in the human placenta. LILRB1 (ILT2) was described mainly on stromal cells, while LILRB2 (ILT4), in addition to stromal cells, was also found around vessels in the smooth muscle layer. In this review we focus on the possible role of polymorphism of KIR, LILRB and their ligands (HLA-C, HLA-G) in susceptibility to recurrent implantation failure, which could serve as diagnostic biomarkers of this disease.