Pregnancy trained decidual NK cells protect pregnancies from harmful Fusobacterium nucleatum infection.

Natural killer cells (NKs) found during pregnancy at the maternal-fetal interface named decidual (d)NKs, show signs of education following first pregnancy, resulting in better placentation and fetus-growth, hence termed pregnancy trained dNKs (PTdNKs). Here we show that PTdNKs provide increased protection of the fetus from Fusobacterium nucleatum (FN) infection. We demonstrate that PTdNKs secrete elevated amounts of the bacteriocidal protein granulysin (GNLY) upon incubation with FN compared to dNKs derived from first pregnancies, which leads to increased killing of FN. Furthermore, we showed mechanistically that the GNLY secretion is mediated through the interaction of the FN's Fap2 protein with Gal-GalNAc present on PTdNKs. Finally, we show in vivo, using GNLY-tg mice that enhanced protection of the fetuses from FN infection is observed, as compared to wild type and that this enhance protection is NK cell dependent. Altogether, we show a new function for PTdNKs as protectors of the fetus from bacterial infection.

Learning from experience: cellular and molecular bases for improved outcome in subsequent pregnancies.

The frequencies of preeclampsia, fetal growth restriction, fetal demise, and low birthweight are lower in subsequent pregnancies. Enhanced maternal cardiovascular adaptation, shorter first and second stages of labor, and more robust lactation also have been observed in subsequent as compared with first pregnancies. We sought to investigate the cellular and molecular bases for better outcomes in subsequent pregnancies. Based on the knowledge that specialized immune cells at the maternal-fetal interface, decidual natural killer cells, promote development of the placental bed and conversion of the spiral arteries by secreting a myriad of angiogenic and growth factors, we asked whether decidual natural killer cells differ in subsequent as compared with first pregnancies. This idea stemmed from recent studies suggesting that natural killer cells, although part of the innate immune system, possess some features of adaptive immunity, including a certain type of immune cell memory, termed trained immunity. We found that decidual natural killer cells from parous women "remember pregnancy" and differ from decidual natural killer cells of primigravidae. Compared with the decidual natural killer cells of first pregnancy, these cells, that we termed pregnancy-trained decidual natural killer cells, express greater levels of the natural killer receptors NKG2C and leukocyte immunoglobulin-like receptor B1, which interact with ligands expressed on invasive trophoblasts. Furthermore, they secrete greater levels of several growth factors, including vascular endothelial growth factor α as well as interferon-γ, augmenting remodeling of the placental bed. We propose that this pregnancy-trained memory dwells in the epigenome, where memory of stimuli is known to persist even when the stimulus is no longer present. This epigenetic memory apparently resides in endometrial natural killer cells between pregnancies. We suggest that this trained memory, which we coined pregnancy-trained decidual natural killer cells, may be the missing link in the immune basis for enhanced subsequent pregnancy. Epigenetic memory (chromatin modification) also may afford a global explanation for additional findings of enhanced maternal cardiovascular adaptation, shorter first and second stages of labor, and more robust lactation. Understanding the molecular and cellular bases of improved outcomes of subsequent pregnancy may lead to the development of treatment modalities designed for women at high risk for pregnancy disorders originating at the maternal-fetal interface.

High percentages and activity of synovial fluid NK cells present in patients with advanced stage active Rheumatoid Arthritis.

Rheumatoid Arthritis (RA) causes chronic inflammation of joints. The cytokines TNFα and IFNγ are central players in RA, however their source has not been fully elucidated. Natural Killer (NK) cells are best known for their role in elimination of viral-infected and transformed cells, and they secrete pro-inflammatory cytokines. NK cells are present in the synovial fluids (SFs) of RA patients and are considered to be important in bone destruction. However, the phenotype and function of NK cells in the SFs of patients with erosive deformative RA (DRA) versus non-deformative RA (NDRA) is poorly characterized. Here we characterize the NK cell populations present in the blood and SFs of DRA and NDRA patients. We demonstrate that a distinct population of activated synovial fluid NK (sfNK) cells constitutes a large proportion of immune cells found in the SFs of DRA patients. We discovered that although sfNK cells in both DRA and NDRA patients have similar phenotypes, they function differently. The DRA sfNK secrete more TNFα and IFNγ upon exposure to IL-2 and IL-15. Consequently, we suggest that sfNK cells may be a marker for more severely destructive RA disease.

IFNG-AS1 Enhances Interferon Gamma Production in Human Natural Killer Cells.

Long, non-coding RNAs (lncRNAs) are involved in the regulation of many cellular processes. The lncRNA IFNG-AS1 was found to strongly influence the responses to several pathogens in mice by increasing interferon gamma (IFNγ) secretion. Studies have looked at IFNG-AS1 in T cells, yet IFNG-AS1 function in natural killer cells (NKs), an important source of IFNγ, remains unknown. Here, we show a previously undescribed sequence of IFNG-AS1 and report that it may be more abundant in cells than previously thought. Using primary human NKs and an NK line with IFNG-AS1 overexpression, we show that IFNG-AS1 is quickly induced upon NK cell activation, and that IFNG-AS1 overexpression leads to increased IFNγ secretion. Taken together, our work expands IFNG-AS1's activity to the innate arm of the type I immune response, helping to explain its notable effect in animal models of disease.

Trained Memory of Human Uterine NK Cells Enhances Their Function in Subsequent Pregnancies.

Natural killer cells (NKs) are abundant in the human decidua, regulating trophoblast invasion and angiogenesis. Several diseases of poor placental development are associated with first pregnancies, so we thus looked to characterize differences in decidual NKs (dNKs) in first versus repeated pregnancies. We discovered a population found in repeated pregnancies, which has a unique transcriptome and epigenetic signature, and is characterized by high expression of the receptors NKG2C and LILRB1. We named these cells Pregnancy Trained decidual NK cells (PTdNKs). PTdNKs have open chromatin around the enhancers of IFNG and VEGFA. Activation of PTdNKs led to increased production and secretion of IFN-γ and VEGFα, with the latter supporting vascular sprouting and tumor growth. The precursors of PTdNKs seem to be found in the endometrium. Because repeated pregnancies are associated with improved placentation, we propose that PTdNKs, which are present primarily in repeated pregnancies, might be involved in proper placentation.

NK Cell Recognition of Candida glabrata through Binding of NKp46 and NCR1 to Fungal Ligands Epa1, Epa6, and Epa7.

Natural killer (NK) cells form an important arm of the innate immune system and function to combat a wide range of invading pathogens, ranging from viruses to bacteria. However, the means by which NK cells accomplish recognition of pathogens with a limited repertoire of receptors remain largely unknown. In the current study, we describe the recognition of an emerging fungal pathogen, Candida glabrata, by the human NK cytotoxic receptor NKp46 and its mouse ortholog, NCR1. Using NCR1 knockout mice, we observed that this receptor-mediated recognition was crucial for controlling C. glabrata infection in vitro and in vivo. Finally, we delineated the fungal ligands to be the C. glabrata adhesins Epa1, Epa6, and Epa7 and demonstrated that clearance of systemic C. glabrata infections in vivo depends on their recognition by NCR1. As NKp46 and NCR1 have been previously shown to bind viral adhesion receptors, we speculate that NKp46/NCR1 may be a novel type of pattern recognition receptor.

Paternal HLA-C and Maternal Killer-Cell Immunoglobulin-Like Receptor Genotypes in the Development of Autism.

Killer-cell immunoglobulin-like receptors (KIRs) are a family of cell surface proteins found on natural killer cells, which are components of the innate immune system. KIRs recognize MHC class I proteins, mainly HLA-C and are further divided into two groups: short-tailed 2/3DS activating receptors and long-tailed 2/3DL inhibitory receptors. Based on the Barker Hypothesis, the origins of illness can be traced back to embryonic development in the uterus, and since KIR:HLA interaction figures prominently in the maternal-fetal interface, we investigated whether specific KIR:HLA combinations may be found in autism spectrum disorders (ASD) children compared with their healthy parents. This study enrolled 49 ASD children from different Israeli families, and their healthy parents. Among the parents, a higher frequency of HLA-C2 allotypes was found in the fathers, while its corresponding ligand 2DS1 was found in higher percentage in the maternal group. However, such skewing in KIR:HLA frequencies did not appear in the ASD children. Additionally, analysis of "overall activation" indicated higher activation in maternal than in paternal cohorts.

PILRα binds an unknown receptor expressed primarily on CD56bright and decidual-NK cells and activates NK cell functions.

Natural Killer (NK) cells are innate immune lymphocytes specializing in recognition and killing of tumors and pathogens, using an array of activating and inhibitory receptors. NK inhibition is mediated by a large repertoire of inhibitory receptors, whereas a limited number of activating NK cell receptors execute NK cell activation. The ligands recognized by the activating receptors are stress-induced, pathogen derived, tumor specific and even self ligands. However, the full spectrum of NK cell receptors and ligands that control NK cell activity remains uncharacterized. Here we demonstrate that Paired Ig-Like type 2 Receptor Alpha (PILRα), binds a distinct human NK cell sub-population present in the peripheral blood and also in the decidua. We further demonstrate that the interaction of NK cells with PILRα expressing targets lead to elevated IFNγ secretion and cytotoxicity. In conclusion, we present here a novel NK activating ligand which binds and activates an unknown NK receptor expressed on a unique NK cell subset.

The oxytocin-CD38-vitamin A axis in pregnant women involves both hypothalamic and placental regulation.

OBJECTIVE: Oxytocin, a hypothalamic hormone secreted upon release of ectoenzyme CD38, plays a vital role in interpersonal bonding behaviors. Reduced plasma oxytocin characterizes autistic individuals. CD38 levels, which were found to be low in LBCs derived from autistic patients, is upregulated upon the addition of a vitamin A derivative. During pregnancy, oxytocin is also secreted by placenta. Recent controversial studies have suggested an increased risk for autism when oxytocin is used during induction and augmentation of labor. We aimed to examine the tripartite relationship between oxytocin, CD38 and vitamin A in pregnant women and their newborns. METHODS: Thirty-one healthy expectant mothers were enlisted for this study. Levels of oxytocin, CD38 and ATRA were measured in both maternal peripheral and newborn cord blood, and the tripartite relationship between these parameters examined. Estrogen and progesterone levels of the mothers were also recorded. Several clinical measures were also noted. RESULTS: Mean maternal oxytocin and vitamin A levels were approximately 8- and 4-fold higher, respectively, than neonatal levels. CD38 expression, however, was 9 times higher in neonates than in the maternal group. Positive correlation was found between maternal and cord blood for both oxytocin and CD38. CONCLUSIONS: This establishment of normative values for oxytocin, CD38 and vitamin A in healthy pregnant women and newborns may serve as a reference in the investigation of developing pathologies of disorders such as autism.

Binding of the Fap2 protein of Fusobacterium nucleatum to human inhibitory receptor TIGIT protects tumors from immune cell attack.

Bacteria, such as Fusobacterium nucleatum, are present in the tumor microenvironment. However, the immunological consequences of intra-tumoral bacteria remain unclear. Here, we have shown that natural killer (NK) cell killing of various tumors is inhibited in the presence of various F. nucleatum strains. Our data support that this F. nucleatum-mediated inhibition is mediated by human, but not by mouse TIGIT, an inhibitory receptor present on all human NK cells and on various T cells. Using a library of F. nucleatum mutants, we found that the Fap2 protein of F. nucleatum directly interacted with TIGIT, leading to the inhibition of NK cell cytotoxicity. We have further demonstrated that tumor-infiltrating lymphocytes expressed TIGIT and that T cell activities were also inhibited by F. nucleatum via Fap2. Our results identify a bacterium-dependent, tumor-immune evasion mechanism in which tumors exploit the Fap2 protein of F. nucleatum to inhibit immune cell activity via TIGIT.

Minor fetal sonographic findings in autism spectrum disorder.

UNLABELLED: Autism spectrum disorder (ASD) is more prevalent in the population than ever before. It is debatable whether this is a real increase in incidence, a change in the diagnostic criteria, or both. The diagnosis is usually made by age 3 years; therefore, obstetricians and fetal-maternal specialists generally display limited awareness of the disorder. Unlike fetuses with chromosomal diseases, which have distinctive physical anomalies, some fetuses that eventually will develop ASD have minor physical anomalies. This is even truer in pregnant women who already have a child with ASD. Those fetuses have a 20 times higher risk of developing ASD than the general population. The more frequent minor physical changes that may be potentially detected by ultrasound are as follows: changes in head circumference (that become more noticeable after 6 months of age), the ratio between the second and the fourth digits, left handedness, and palatal changes. TARGET AUDIENCE: Obstetricians, Maternal - Fetal Medicine specialists, Pediatricians, Sonographers LEARNING OBJECTIVES: After completing this CME activity, physicians should better able to classify the increasing prevalence of this disorder, and to assess the minor physical changes in fetuses that some may be seen on ultrasound during pregnancy.

KIF1A missense mutations in SPG30, an autosomal recessive spastic paraplegia: distinct phenotypes according to the nature of the mutations.

The hereditary spastic paraplegias (HSPs) are a clinically and genetically heterogeneous group of neurodegenerative diseases characterised by progressive spasticity in the lower limbs. The nosology of autosomal recessive forms is complex as most mapped loci have been identified in only one or a few families and account for only a small percentage of patients. We used next-generation sequencing focused on the SPG30 chromosomal region on chromosome 2q37.3 in two patients from the original linked family. In addition, wide genome scan and candidate gene analysis were performed in a second family of Palestinian origin. We identified a single homozygous mutation, p.R350G, that was found to cosegregate with the disease in the SPG30 kindred and was absent in 970 control chromosomes while affecting a strongly conserved amino acid at the end of the motor domain of KIF1A. Homozygosity and linkage mapping followed by mutation screening of KIF1A allowed us to identify a second mutation, p.A255V, in the second family. Comparison of the clinical features with the nature of the mutations of all reported KIF1A families, including those reported recently with hereditary sensory and autonomic neuropathy, suggests phenotype-genotype correlations that may help to understand the mechanisms involved in motor neuron degeneration. We have shown that mutations in the KIF1A gene are responsible for SPG30 in two autosomal recessive HSP families. In published families, the nature of the KIF1A mutations seems to be of good predictor of the underlying phenotype and vice versa.