Modulation of NK cell function by genetically coupled C-type lectin-like receptor/ligand pairs encoded in the human natural killer gene complex

The shared circulating diagnostic biomarkers and molecular mechanisms of systemic lupus erythematosus and inflammatory bowel disease

Background

Systemic lupus erythematosus (SLE) is a multi-organ chronic autoimmune disease. Inflammatory bowel disease (IBD) is a common chronic inflammatory disease of the gastrointestinal tract. Previous studies have shown that SLE and IBD share common pathogenic pathways and genetic susceptibility, but the specific pathogenic mechanisms remain unclear.

Methods

The datasets of SLE and IBD were downloaded from the Gene Expression Omnibus (GEO). Differentially expressed genes (DEGs) were identified using the Limma package. Weighted gene coexpression network analysis (WGCNA) was used to determine co-expression modules related to SLE and IBD. Pathway enrichment was performed using Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis for co-driver genes. Using the Least AbsoluteShrinkage and Selection Operator (Lasso) regressionand Support Vector Machine-Recursive Feature Elimination (SVM-RFE), common diagnostic markers for both diseases were further evaluated. Then, we utilizedthe CIBERSORT method to assess the abundance of immune cell infiltration. Finally,we used the single-cell analysis to obtain the location of common diagnostic markers.

Results

71 common driver genes were identified in the SLE and IBD cohorts based on the DEGs and module genes. KEGG and GO enrichment results showed that these genes were closely associated with positive regulation of programmed cell death and inflammatory responses. By using LASSO regression and SVM, five hub genes (KLRF1, GZMK, KLRB1, CD40LG, and IL-7R) were ultimately determined as common diagnostic markers for SLE and IBD. ROC curve analysis also showed good diagnostic performance. The outcomes of immune cell infiltration demonstrated that SLE and IBD shared almost identical immune infiltration patterns. Furthermore, the majority of the hub genes were commonly expressed in NK cells by single-cell analysis.

Conclusion

This study demonstrates that SLE and IBD share common diagnostic markers and pathogenic pathways. In addition, SLE and IBD show similar immune cellinfiltration microenvironments which provides newperspectives for future treatment.

ITAM-based receptors in natural killer cells

The ability of cells of the immune system to acquire features such as increased longevity and enhanced secondary responses was long thought to be restricted to cells of the adaptive immune system. Natural killer (NK) cells have challenged this notion by demonstrating that they can also gain adaptive features. This has been observed in both humans and mice during infection with cytomegalovirus (CMV). The generation of adaptive NK cells requires antigen-specific recognition of virally infected cells through stimulatory NK receptors. These receptors lack the ability to signal on their own and rather rely on adaptor molecules that contain ITAMs for driving signals. Here, we highlight our understanding of how these receptors influence the production of adaptive NK cells and propose areas in the field that merit further investigation.

The activating receptor NKp65 is selectively expressed by human ILC3 and demarcates ILC3 from mature NK cells

Innate lymphocytes comprise cytotoxic natural killer (NK) cells and tissue-resident innate lymphoid cells (ILC) that are subgrouped according to their cytokine profiles into group 1 ILC (ILC1), ILC2, and ILC3. However, cell surface receptors unambiguously defining or specifically activating such ILC subsets are scarcely known. Here, we report on the physiologic expression of the human activating C-type lectin-like receptor (CTLR) NKp65, a high-affinity receptor for the CTLR keratinocyte-associated C-type lectin (KACL). Tracking rare NKp65 transcripts in human blood, we identify ILC3 to selectively express NKp65. NKp65 expression not only demarcates "bona fide" ILC3 from likewise RORγt-expressing ILC precursors and lymphoid tissue inducer cells but also from mature NK cells which acquire the NKp65-relative NKp80 during a Notch-dependent differentiation from NKp65+ precursor cells. Hence, ILC3 and NK cells mutually exclusively and interdependently express the genetically coupled sibling receptors NKp65 and NKp80. Much alike NKp80, NKp65 promotes cytotoxicity by innate lymphocytes which may become relevant during pathophysiological reprogramming of ILC3. Altogether, we report the selective expression of the activating immunoreceptor NKp65 by ILC3 demarcating ILC3 from mature NK cells and endowing ILC3 with a dedicated immunosensor for the epidermal immune barrier.

A new chromosome-scale duck genome shows a major histocompatibility complex with several expanded multigene families

BACKGROUND

The duck (Anas platyrhynchos) is one of the principal natural hosts of influenza A virus (IAV), harbors almost all subtypes of IAVs and resists to many IAVs which cause extreme virulence in chicken and human. However, the response of duck's adaptive immune system to IAV infection is poorly characterized due to lack of a detailed gene map of the major histocompatibility complex (MHC).

RESULTS

We herein reported a chromosome-scale Beijing duck assembly by integrating Nanopore, Bionano, and Hi-C data. This new reference genome SKLA1.0 covers 40 chromosomes, improves the contig N50 of the previous duck assembly with highest contiguity (ZJU1.0) of more than a 5.79-fold, surpasses the chicken and zebra finch references in sequence contiguity and contains a complete genomic map of the MHC. Our 3D MHC genomic map demonstrated that gene family arrangement in this region was primordial; however, families such as AnplMHCI, AnplMHCIIβ, AnplDMB, NKRL (NK cell receptor-like genes) and BTN underwent gene expansion events making this area complex. These gene families are distributed in two TADs and genes sharing the same TAD may work in a co-regulated model.

CONCLUSIONS

These observations supported the hypothesis that duck's adaptive immunity had been optimized with expanded and diversified key immune genes which might help duck to combat influenza virus. This work provided a high-quality Beijing duck genome for biological research and shed light on new strategies for AIV control.

Dectin-1 multimerization and signaling depends on fungal β-glucan structure and exposure

Dectin-1A is a C-type lectin innate immunoreceptor that recognizes β-(1,3;1,6)-glucan, a structural component of Candida species cell walls. β-Glucans can adopt solution structures ranging from random coil to insoluble fiber due to tertiary (helical) and quaternary structure. Fungal β-glucans of medium and high molecular weight are highly structured, but low molecular weight glucan is much less structured. Despite similar affinity for Dectin-1, the ability of glucans to induce Dectin-1A-mediated signaling correlates with degree of structure. Glucan denaturation experiments showed that glucan structure determines agonistic potential, but not receptor binding affinity. We explored the impact of glucan structure on molecular aggregation of Dectin-1A. Stimulation with glucan signaling decreased Dectin-1A diffusion coefficient. Fluorescence measurements provided direct evidence of ligation-induced Dectin-1A aggregation, which positively correlated with increasing glucan structure content. In contrast, Dectin-1A is predominantly in a low aggregation state in resting cells. Molecular aggregates formed during interaction with highly structured, agonistic glucans did not exceed relatively small (<15 nm) clusters of a few engaged receptors. Finally, we observed increased molecular aggregation of Dectin-1A at fungal particle contact sites in a manner that positively correlated with the degree of exposed glucan on the particle surface. These results indicate that Dectin-1A senses the solution conformation of β-glucans through their varying ability to drive receptor dimer/oligomer formation and activation of membrane proximal signaling events.

Understanding NK cell biology for harnessing NK cell therapies: targeting cancer and beyond

Gene-engineered immune cell therapies have partially transformed cancer treatment, as exemplified by the use of chimeric antigen receptor (CAR)-T cells in certain hematologic malignancies. However, there are several limitations that need to be addressed to target more cancer types. Natural killer (NK) cells are a type of innate immune cells that represent a unique biology in cancer immune surveillance. In particular, NK cells obtained from heathy donors can serve as a source for genetically engineered immune cell therapies. Therefore, NK-based therapies, including NK cells, CAR-NK cells, and antibodies that induce antibody-dependent cellular cytotoxicity of NK cells, have emerged. With recent advances in genetic engineering and cell biology techniques, NK cell-based therapies have become promising approaches for a wide range of cancers, viral infections, and senescence. This review provides a brief overview of NK cell characteristics and summarizes diseases that could benefit from NK-based therapies. In addition, we discuss recent preclinical and clinical investigations on the use of adoptive NK cell transfer and agents that can modulate NK cell activity.

Cytotoxic CD161-CD8+ TEMRA cells contribute to the pathogenesis of systemic lupus erythematosus

BACKGROUND

Systemic lupus erythematosus (SLE) is a prototypical autoimmune disease affecting multiple organs and tissues with high cellular heterogeneity. CD8⁺ T cell activity is involved in the SLE pathogenesis. However, the cellular heterogeneity and the underlying mechanisms of CD8⁺ T cells in SLE remain to be identified.

METHODS

Single-cell RNA sequencing (scRNA-seq) of PBMCs from a SLE family pedigree (including 3 HCs and 2 SLE patients) was performed to identify the SLE-associated CD8⁺ T cell subsets. Flow cytometry analysis of a SLE cohort (including 23 HCs and 33 SLE patients), qPCR analysis of another SLE cohort (including 30 HCs and 25 SLE patients) and public scRNA-seq datasets of autoimmune diseases were employed to validate the finding. Whole-exome sequencing (WES) of this SLE family pedigree was used to investigate the genetic basis in dysregulation of CD8⁺ T cell subsets identified in this study. Co-culture experiments were performed to analyze the activity of CD8⁺ T cells.

FINDINGS

We elucidated the cellular heterogeneity of SLE and identified a new highly cytotoxic CD8⁺ T cell subset, CD161^-CD8⁺ T_EMRA cell subpopulation, which was remarkably increased in SLE patients. Meanwhile, we discovered a close correlation between mutation of DTHD1 and the abnormal accumulation of CD161^-CD8⁺ T_EMRA cells in SLE. DTHD1 interacted with MYD88 to suppress its activity in T cells and DTHD1 mutation promoted MYD88-dependent pathway and subsequently increased the proliferation and cytotoxicity of CD161^-CD8⁺ T_EMRA cells. Furthermore, the differentially expressed genes in CD161^-CD8⁺ T_EMRA cells displayed a strong out-of-sample prediction for case-control status of SLE.

INTERPRETATION

This study identified DTHD1-associated expansion of CD161^-CD8⁺ T_EMRA cell subpopulation is critical for SLE. Our study highlights genetic association and cellular heterogeneity of SLE pathogenesis and provides a mechanistical insight into the diagnosis and treatment of SLE.

FUNDINGS

Stated in the Acknowledgements section of the manuscript.

Single-Cell Transcriptomic Analysis of Primary and Metastatic Tumor Ecosystems in Esophageal Squamous Cell Carcinoma

Lymph node metastasis, the leading cause of mortality in esophageal squamous carcinoma (ESCC) with a highly complex tumor microenvironment, remains underexplored. Here, the transcriptomes of 85 263 single cells are analyzed from four ESCC patients with lymph node metastases. Strikingly, it is observed that the metastatic microenvironment undergoes the emergence or expansion of interferon induced IFIT3+ T, B cells, and immunosuppressive cells such as APOC1+ APOE+ macrophages and myofibroblasts with highly expression of immunoglobulin genes (IGKC) and extracellular matrix component and matrix metallopeptidase genes. A poor-prognostic epithelial-immune dual expression program regulating immune effector processes, whose activity is significantly enhanced in metastatic malignant epithelial cells and enriched in CD74+ CXCR4+ and major histocompatibility complex (MHC) class II genes upregulated malignant epithelia cells is discovered. Comparing with primary tumor, differential intercellular communications of metastatic ESCC microenvironment are revealed and furtherly validated via multiplexed immunofluorescence and immunohistochemistry staining, which mainly rely on the crosstalk of APOC1+ APOE+ macrophages with tumor and stromal cell. The data highlight potential molecular mechanisms that shape the lymph-node metastatic microenvironment and may inform drug discovery and the development of new strategies to target these prometastatic nontumor components for inhibiting tumor growth and overcoming metastasis to improve clinical outcomes.

Transcriptional reprogramming of natural killer cells by vaccinia virus shows both distinct and conserved features with mCMV

Natural killer (NK) cells have an established role in controlling poxvirus infection and there is a growing interest to exploit their capabilities in the context of poxvirus-based oncolytic therapy and vaccination. How NK cells respond to poxvirus-infected cells to become activated is not well established. To address this knowledge gap, we studied the NK cell response to vaccinia virus (VACV) in vivo, using a systemic infection murine model. We found broad alterations in NK cells transcriptional activity in VACV-infected mice, consistent with both direct target cell recognition and cytokine exposure. There were also alterations in the expression levels of specific NK surface receptors (NKRs), including the Ly49 family and SLAM receptors, as well as upregulation of memory-associated NK markers. Despite the latter observation, adoptive transfer of VACV-expercienced NK populations did not confer protection from infection. Comparison with the NK cell response to murine cytomegalovirus (MCMV) infection highlighted common features, but also distinct NK transcriptional programmes initiated by VACV. Finally, there was a clear overlap between the NK transcriptional response in humans vaccinated with an attenuated VACV, modified vaccinia Ankara (MVA), demonstrating conservation between the NK response in these different host species. Overall, this study provides new data about NK cell activation, function, and homeostasis during VACV infection, and may have implication for the design of VACV-based therapeutics.

Diminished function of cytotoxic T- and NK- cells in severe alcohol-associated hepatitis

Aim

Metabolic liver diseases, including alcohol- and non-alcoholic fatty liver diseases (ALD/NAFLD), are characterized by inflammation and decreased ability to prevent infections. Patients with severe alcohol-associated hepatitis (sAH) are particularly susceptible to infections while undergoing treatment with steroids. Understanding the immunological mechanisms for these responses is critical to managing the treatment of patients with metabolic liver diseases. Cytotoxic NK cells and CD8 T cells, using cytolytic granules, serve an important immunological role by killing infected cells, including monocytes. However, patients with sAH have dysfunctional NK cells, which cannot kill target cells, though the mechanism is unknown.

Method

We performed an exploratory study using single-cell RNA-seq (scRNA-seq) (n = 4) and multi-panel intracellular flow cytometry (n = 7-8 for all patient groups) on PBMCs isolated from patients with sAH and healthy controls (HC).

Results

ScRNA-seq revealed receptors in NK cells and CD8 T cells required for cytotoxic cell recognition of activated monocytes were downregulated in patients with sAH compared to healthy controls. Granulysin was the most downregulated gene in both NK cells and effector CD8 T cells. In NK cells from HC, expression of granulysin, perforin, and granzymes A and B was highly correlated; however, in sAH, these genes lost coordinate expression, indicative of dysfunctional cytolytic granule formation. Finally, the expression of cytolytic granule proteins in NK cells was decreased from sAH, indicating reduced cytolytic granules.

Conclusion

Together, these results suggest a loss of cytotoxic cell function in PBMCs from sAH that may contribute to a decreased ability to communicate with other immune cells, such as monocytes, and prevent the killing of infected cells, thus increasing the risk of infection.

Carcinogenesis resistance in the longest-lived rodent, the naked mole-rat

Certain mammalian species are resistant to cancer, and a better understanding of how this cancer resistance arises could provide valuable insights for basic cancer research. Recent technological innovations in molecular biology have allowed the study of cancer-resistant mammals, despite the fact that they are not the classical model animals, which are easily studied using genetic approaches. Naked mole-rats (NMRs; Heterocephalus glaber) are the longest-lived rodent, with a maximum lifespan of more than 37 years, and almost never show spontaneous carcinogenesis. NMRs are currently attracting much attention from aging and cancer researchers, and published studies on NMR have continued to increase over the past decade. Cancer development occurs via multiple steps and involves many biological processes. Recent research on the NMR as a model for cancer resistance suggests that they possess various unique carcinogenesis-resistance mechanisms, including efficient DNA repair pathways, cell-autonomous resistance to transformation, and dampened inflammatory response. Here, we summarize the molecular mechanisms of carcinogenesis resistance in NMR, which have been uncovered over the past two decades, and discuss future perspectives.

Mouse Ocilrp2/Clec2i negatively regulates LPS-mediated IL-6 production by blocking Dap12-Syk interaction in macrophage

C-type lectin Ocilrp2/Clec2i is widely expressed in dendritic cells, lymphokine-activated killer cells and activated T cells. Previous studies have shown that Ocilrp2 is an important regulator in the activation of T cells and NK cells. However, the role of Ocilrp2 in the inflammatory responses by activated macrophages is currently unknown. This study investigated the expression of inflammatory cytokines in LPS-induced macrophages from primary peritoneal macrophages silenced by specific siRNA target Ocilrp2. Ocilrp2 was significantly downregulated in macrophages via NF-κB and pathways upon LPS stimuli or VSV infection. Silencing Ocilrp2 resulted in the increased expression of IL-6 in LPS-stimulated peritoneal macrophages and mice. Moreover, IL-6 expression was reduced in LPS-induced Ocilrp2 over-expressing iBMDM cells. Furthermore, we found that Ocilrp2-related Syk activation is responsible for expressing inflammatory cytokines in LPS-stimulated macrophages. Silencing Ocilrp2 significantly promotes the binding of Syk to Dap12. Altogether, we identified the Ocilrp2 as a critical role in the TLR4 signaling pathway and inflammatory macrophages’ immune regulation, and added mechanistic insights into the crosstalk between TLR and Syk signaling.

Structure of the human NK cell NKR-P1:LLT1 receptor:ligand complex reveals clustering in the immune synapse

Signaling by the human C-type lectin-like receptor, natural killer (NK) cell inhibitory receptor NKR-P1, has a critical role in many immune-related diseases and cancer. C-type lectin-like receptors have weak affinities to their ligands; therefore, setting up a comprehensive model of NKR-P1-LLT1 interactions that considers the natural state of the receptor on the cell surface is necessary to understand its functions. Here we report the crystal structures of the NKR-P1 and NKR-P1:LLT1 complexes, which provides evidence that NKR-P1 forms homodimers in an unexpected arrangement to enable LLT1 binding in two modes, bridging two LLT1 molecules. These interaction clusters are suggestive of an inhibitory immune synapse. By observing the formation of these clusters in solution using SEC-SAXS analysis, by dSTORM super-resolution microscopy on the cell surface, and by following their role in receptor signaling with freshly isolated NK cells, we show that only the ligation of both LLT1 binding interfaces leads to effective NKR-P1 inhibitory signaling. In summary, our findings collectively support a model of NKR-P1:LLT1 clustering, which allows the interacting proteins to overcome weak ligand-receptor affinity and to trigger signal transduction upon cellular contact in the immune synapse.

NKR-P1 is an inhibitory receptor on the surface of natural killer cells, and its engagement with the ligand LLT1 on activated monocytes and B cells triggers NK cell self-tolerance and other immunological processes. Here authors set up a comprehensive, structure-based model of NKR-P1-LLT1 interaction that involves NKR-P1 homodimer formation and subsequent bridging of two LLT1 molecules.

Natural killer cells in antiviral immunity

Natural killer (NK) cells play an important role in innate immune responses to viral infections. Here, we review recent insights into the role of NK cells in viral infections, with particular emphasis on human studies. We first discuss NK cells in the context of acute viral infections, with flavivirus and influenza virus infections as examples. Questions related to activation of NK cells, homing to infected tissues and the role of tissue-resident NK cells in acute viral infections are also addressed. Next, we discuss NK cells in the context of chronic viral infections with hepatitis C virus and HIV-1. Also covered is the role of adaptive-like NK cell expansions as well as the appearance of CD56- NK cells in the course of chronic infection. Specific emphasis is then placed in viral infections in patients with primary immunodeficiencies affecting NK cells. Not least, studies in this area have revealed an important role for NK cells in controlling several herpesvirus infections. Finally, we address new data with respect to the activation of NK cells and NK cell function in humans infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) giving rise to coronavirus disease 2019 (COVID-19).

Immune Response to Viruses

Viruses are essentially, obligate intracellular parasites. They require a host to replicate their genetic material, spread to other cells, and eventually to other hosts. For humans, most viral infections are not considered lethal, regardless if at the cellular level, the virus can obliterate individual cells. Constant genomic mutations, (which can alter the antigenic content of viruses such as influenza or coronaviruses), zoonosis or immunosuppression/immunocompromisation, is when viruses achieve higher host mortality. Frequent examples of the severe consequenses of viral infection can be seen in children and the elderly. In most instances, the immune system will take a multifaceted approach in defending the host against viruses. Depending on the virus, the individual, and the point of entry, the immune system will initiate a robust response which involves multiple components. In this chapter, we expand on the total immune system, breaking it down to the two principal types: Innate and Adaptive Immunity, their different roles in viral recognition and clearance. Finally, how different viruses activate and evade different arms of the immune system.

Natural killer cells in liver transplantation: Can we harness the power of the immune checkpoint to promote tolerance?

The roles that natural killer (NK) cells play in liver disease and transplantation remain ill‐defined. Reports on the matter are often contradictory, and the mechanisms elucidated are complex and dependent on the context of the model tested. Moreover, NK cell attributes, such as receptor protein expression and function differ among species, make study of primate or rodent transplant models challenging. Recent insights into NK function and NK‐mediated therapy in the context of cancer therapy may prove applicable to transplantation. Of specific interest are immune checkpoint molecules and the mechanisms by which they modulate NK cells in the tumor micro‐environment. In this review, we summarize NK cell populations in the peripheral blood and liver, and we explore the data regarding the expression and function of immune checkpoint molecules on NK cells. We also hypothesize about the roles they could play in liver transplantation and discuss how they might be harnessed therapeutically in transplant sciences.

Approaches to Enhance Natural Killer Cell-Based Immunotherapy for Pediatric Solid Tumors

Treatment of metastatic pediatric solid tumors remain a significant challenge, particularly in relapsed and refractory settings. Standard treatment has included surgical resection, radiation, chemotherapy, and, in the case of neuroblastoma, immunotherapy. Despite such intensive therapy, cancer recurrence is common, and most tumors become refractory to prior therapy, leaving patients with few conventional treatment options. Natural killer (NK) cells are non-major histocompatibility complex (MHC)-restricted lymphocytes that boast several complex killing mechanisms but at an added advantage of not causing graft-versus-host disease, making use of allogeneic NK cells a potential therapeutic option. On top of their killing capacity, NK cells also produce several cytokines and growth factors that act as key regulators of the adaptive immune system, positioning themselves as ideal effector cells for stimulating heavily pretreated immune systems. Despite this promise, clinical efficacy of adoptive NK cell therapy to date has been inconsistent, prompting a detailed understanding of the biological pathways within NK cells that can be leveraged to develop "next generation" NK cell therapies. Here, we review advances in current approaches to optimizing the NK cell antitumor response including combination with other immunotherapies, cytokines, checkpoint inhibition, and engineering NK cells with chimeric antigen receptors (CARs) for the treatment of pediatric solid tumors.

Circulating NKG2A-NKG2D+ CD56dimCD16+ Natural Killer (NK) Cells as Mediators of Functional Immunosurveillance in Kidney Transplant Recipients

Background

Recently, in patients with long-term functioning allografts, we showed that high NKG2D+ NK cell numbers in the peripheral blood were associated with a higher glomerular filtration rate, whereas high NKG2A+ NK cells were associated with a lower glomerular filtration rate. Both NK cell determinants react with ligands (MIC A/B, HLA-E) expressed on stressed cells, such as virus-infected cells, tumor cells, or cells activated during graft rejection. In the present study, we attempted to characterize these 2 NK cell subsets further.

Material/Methods

Using flow cytometry, NK cell subsets were analyzed in whole-blood samples of 35 stable kidney transplant recipients (serum creatinine mean±SD: 1.44±0.45 mg/dl). Blood was obtained 95–3786 days after transplant (mean±SD: 1168±1011 days after transplant).

Results

High proportions of NKG2A–NKG2D+ NK cells were strongly associated with high numbers of CD56dimCD16+ (p=0.001) NK cells co-expressing CD107 (P=0.001) and granzyme B (P=0.045), suggesting that NKG2A–NKG2D+ NK cells are predominantly cytotoxic. In contrast, high numbers of NKG2A+NKG2D− NK cells were strongly associated with low numbers of CD56dimCD16+ NK cells expressing CD107 (P=0.026), CD25 (p=0.008), TGF-βR (P=0.028), and TGF-β (P=0.005), suggesting that patients with high proportions of NKG2A+NKG2D− NK cells have low proportions of NK cell subsets with cytotoxic phenotype.

Conclusions

A high proportion of NKG2A+NKG2D− NK cells is associated with decreased counts of NKG2A–NKG2D+ CD56dimCD16+ cytotoxic NK cells in the circulation. This may result in impaired immunosurveillance. We would like to hypothesize that NKG2A–NKG2D+ CD56dimCD16+ cytotoxic NK cells eliminate MIC A/B-expressing stressed cells which possess a potential to harm the transplant. Further studies will have to evaluate whether the proportion of NKG2A–NKG2D+ CD56dimCD16+ cytotoxic NK cells is a useful biomarker for the prediction of an uncomplicated postoperative course in kidney transplant recipients.

Protective Vaccination Reshapes Hepatic Response to Blood-Stage Malaria of Genes Preferentially Expressed by NK Cells

The role of natural killer (NK) cells in the liver as first-line post infectionem (p.i.) effectors against blood-stage malaria and their responsiveness to protective vaccination is poorly understood. Here, we investigate the effect of vaccination on NK cell-associated genes induced in the liver by blood-stage malaria of Plasmodium chabaudi. Female Balb/c mice were vaccinated at weeks 3 and 1 before being infected with 10⁶P. chabaudi-parasitized erythrocytes. Genes preferentially expressed by NK cells were investigated in livers of vaccination-protected and non-protected mice on days 0, 1, 4, 8, and 11 p.i. using microarrays, qRT-PCR, and chromosome landscape analysis. Blood-stage malaria induces expression of specific genes in the liver at different phases of infection, i.e., Itga1 in expanding liver-resident NK (lrNK) cells, Itga2 in immigrating conventional NK (cNK) cells; Eomes and Tbx21 encoding transcription factors; Ncr1, Tnfsf10, Prf1, Gzma, Gzmb, Gzmc, Gzmm, and Gzmk encoding cytolytic effectors; natural killer gene complex (NKC)-localized genes encoding the NK cell receptors KLRG1, KLRK1, KLRAs1, 2, 5, 7, KLRD1, KLRC1, KLRC3, as well as the three receptors KLRB1A, KLRB1C, KLRB1F and their potential ligands CLEC2D and CLEC2I. Vaccination enhances this malaria-induced expression of genes, but impairs Gzmm expression, accelerates decline of Tnfsf10 and Clec2d expression, whereas it accelerates increased expression of Clec2i, taking a very similar time course as that of genes encoding plasma membrane proteins of erythroblasts, whose malaria-induced extramedullary generation in the liver is known to be accelerated by vaccination. Collectively, vaccination reshapes the response of the liver NK cell compartment to blood-stage malaria. Particularly, the malaria-induced expansion of lrNK cells peaking on day 4 p.i. is highly significantly (p < 0.0001) reduced by enhanced immigration of peripheral cNK cells, and KLRB1F:CLEC2I interactions between NK cells and erythroid cells facilitate extramedullary erythroblastosis in the liver, thus critically contributing to vaccination-induced survival of otherwise lethal blood-stage malaria of P. chabaudi.

NKp30 - A prospective target for new cancer immunotherapy strategies

Natural killer (NK) cells are an important arm of the innate immune system. They constitutively express the NKp30 receptor. NKp30-mediated responses are triggered by the binding of specific ligands e.g. tumour cell-derived B7-H6 and involve the secretion of cytotoxic mediators including TNF-α, IFN-γ, perforins and granzymes. The latter two constitute a target cell-directed response that is critical in the process of immunosurveillance. The structure of NKp30 is presented, focusing on the ligand-binding site, on the ligand-induced structural changes and on the experimental data available correlating structure and binding affinity. The translation of NKp30 structural changes to disease progression is also reviewed. NKp30 role in immunotherapy has been explored in chimeric antigen receptor T-cell (CAR-T) therapy. However, antibodies or small ligands targeting NKp30 have not yet been developed. The data reviewed herein unveil the key structural aspects that must be considered for drug design in order to develop novel immunotherapy approaches.

MDA-9/Syntenin (SDCBP): Novel gene and therapeutic target for cancer metastasis

The primary cause of cancer-related death from solid tumors is metastasis. While unraveling the mechanisms of this complicated process continues, our ability to effectively target and treat it to decrease patient morbidity and mortality remains disappointing. Early detection of metastatic lesions and approaches to treat metastases (both pharmacological and genetic) are of prime importance to obstruct this process clinically. Metastasis is complex involving both genetic and epigenetic changes in the constantly evolving tumor cell. Moreover, many discrete steps have been identified in metastatic spread, including invasion, intravasation, angiogenesis, attachment at a distant site (secondary seeding), extravasation and micrometastasis and tumor dormancy development. Here, we provide an overview of the metastatic process and highlight a unique pro-metastatic gene, melanoma differentiation associated gene-9/Syntenin (MDA-9/Syntenin) also called syndecan binding protein (SDCBP), which is a major contributor to the majority of independent metastatic events. MDA-9 expression is elevated in a wide range of carcinomas and other cancers, including melanoma, glioblastoma multiforme and neuroblastoma, suggesting that it may provide an appropriate target to intervene in metastasis. Pre-clinical studies confirm that inhibiting MDA-9 either genetically or pharmacologically profoundly suppresses metastasis. An additional benefit to blocking MDA-9 in metastatic cells is sensitization of these cells to a second therapeutic agent, which converts anti-invasion effects to tumor cytocidal effects. Continued mechanistic and therapeutic insights hold promise to advance development of truly effective therapies for metastasis in the future.

Integrated, multicohort analysis reveals unified signature of systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a complex autoimmune disease that follows an unpredictable disease course and affects multiple organs and tissues. We performed an integrated, multicohort analysis of 7,471 transcriptomic profiles from 40 independent studies to identify robust gene expression changes associated with SLE. We identified a 93-gene signature (SLE MetaSignature) that is differentially expressed in the blood of patients with SLE compared with healthy volunteers; distinguishes SLE from other autoimmune, inflammatory, and infectious diseases; and persists across diverse tissues and cell types. The SLE MetaSignature correlated significantly with disease activity and other clinical measures of inflammation. We prospectively validated the SLE MetaSignature in an independent cohort of pediatric patients with SLE using a microfluidic quantitative PCR (qPCR) array. We found that 14 of the 93 genes in the SLE MetaSignature were independent of IFN-induced and neutrophil-related transcriptional profiles that have previously been associated with SLE. Pathway analysis revealed dysregulation associated with nucleic acid biosynthesis and immunometabolism in SLE. We further refined a neutropoiesis signature and identified underappreciated transcripts related to immune cells and oxidative stress. In our multicohort, transcriptomic analysis has uncovered underappreciated genes and pathways associated with SLE pathogenesis, with the potential to advance clinical diagnosis, biomarker development, and targeted therapeutics for SLE.

Recalling the Biological Significance of Immune Checkpoints on NK Cells: A Chance to Overcome LAG3, PD1, and CTLA4 Inhibitory Pathways by Adoptive NK Cell Transfer?

Immune checkpoint receptors (IC) positively or negatively regulate the activation of the host immune response, preventing unwanted reactions against self-healthy tissues. In recent years the term IC has been mainly used for the inhibitory ICs, which are critical to control Natural Killer (NK) and Cytotoxic CD8⁺ T cells due to its high cytotoxic potential. Due to the different nature of the signals that regulate T and NK cell activation, specific ICs have been described that mainly regulate either NK cell or T cell activity. Thus, strategies to modulate NK cell activity are raising as promising tools to treat tumors that do not respond to T cell-based immunotherapies. NK cell activation is mainly regulated by ICs and receptors from the KIR, NKG2 and NCRs families and the contribution of T cell-related ICs is less clear. Recently, NK cells have emerged as contributors to the effect of inhibitors of T cell-related ICs like CTLA4, LAG3 or the PD1/PD-L1 axes in cancer patients, suggesting that these ICs also regulate the activity of NK cells under pathological conditions. Strikingly, in contrast to NK cells from cancer patients, the level of expression of these ICs is low on most subsets of freshly isolated and in vitro activated NK cells from healthy patients, suggesting that they do not control NK cell tolerance and thus, do not act as conventional ICs under non-pathological conditions. The low level of expression of T cell-related ICs in “healthy” NK cells suggest that they should not be restricted to the detrimental effects of these inhibitory mechanisms in the cancer microenvironment. After a brief introduction of the regulatory mechanisms that control NK cell anti-tumoral activity and the conventional ICs controlling NK cell tolerance, we will critically discuss the potential role of T cell-related ICs in the control of NK cell activity under both physiological and pathological (cancer) conditions. This discussion will allow to comprehensively describe the chances and potential limitations of using allogeneic NK cells isolated from a healthy environment to overcome immune subversion by T cell-related ICs and to improve the efficacy of IC inhibitors (ICIs) in a safer way.

Flow cytometric identification and cell-line establishment of macrophages in naked mole-rats

Naked mole rats (NMRs) have extraordinarily long lifespans and anti-tumorigenic capability. Recent studies of humans and mice have shown that many age-related diseases, including cancer, are strongly correlated with immunity, and macrophages play particularly important roles in immune regulation. Therefore, NMR macrophages may contribute to their unique phenotypes. However, studies of the roles of macrophages are limited by material restrictions and the lack of an established experimental strategy. In this study, we developed a flow cytometric strategy to identify NMR macrophages. The NMR macrophages were extractable using an off-the-shelf anti-CD11b antibody, M1/70, and forward/side scatter data obtained by flow cytometry. NMR macrophages proliferated in response to human/mouse recombinant M-CSF and engulfed Escherichia coli particles. Interestingly, the majority of NMR macrophages exhibited co-staining with an anti-NK1.1 antibody, PK136. NK1.1 antigen crosslinking with PK136 results in mouse NK cell stimulation; similarly, NMR macrophages proliferated in response to NK1.1 antibody treatment. Furthermore, we successfully established an NMR macrophage cell line, NPM1, by transduction of Simian virus 40 early region that proliferated indefinitely without cytokines and retained its phagocytotic capacity. The NPM1 would contribute to further studies on the immunity of NMRs.

Production of recombinant soluble dimeric C-type lectin-like receptors of rat natural killer cells

Working at the border between innate and adaptive immunity, natural killer (NK) cells play a key role in the immune system by protecting healthy cells and by eliminating malignantly transformed, stressed or virally infected cells. NK cell recognition of a target cell is mediated by a receptor “zipper” consisting of various activating and inhibitory receptors, including C-type lectin-like receptors. Among this major group of receptors, two of the largest rodent receptor families are the NKR-P1 and the Clr receptor families. Although these families have been shown to encode receptor-ligand pairs involved in MHC-independent self-nonself discrimination and are a target for immune evasion by tumour cells and viruses, structural mechanisms of their mutual recognition remain less well characterized. Therefore, we developed a non-viral eukaryotic expression system based on transient transfection of suspension-adapted human embryonic kidney 293 cells to produce soluble native disulphide dimers of NK cell C-type lectin-like receptor ectodomains. The expression system was optimized using green fluorescent protein and secreted alkaline phosphatase, easily quantifiable markers of recombinant protein production. We describe an application of this approach to the recombinant protein production and characterization of native rat NKR-P1B and Clr-11 proteins suitable for further structural and functional studies.

NK Cells as Potential Targets for Immunotherapy in Endometriosis

Endometriosis is a common gynecological disease defined by the presence of endometrial-like tissue outside the uterus, most frequently on the pelvic viscera and ovaries, which is associated with pelvic pains and infertility. It is an inflammatory disorder with some features of autoimmunity. It is accepted that ectopic endometriotic tissue originates from endometrial cells exfoliated during menstruation and disseminating into the peritoneum by retrograde menstrual blood flow. It is assumed that the survival of endometriotic cells in the peritoneal cavity may be partially due to their abrogated elimination by natural killer (NK) cells. The decrease of NK cell cytotoxic activity in endometriosis is associated with an increased expression of some inhibitory NK cell receptors. It may be also related to the expression of human leukocyte antigen G (HLA-G), a ligand for inhibitory leukocyte immunoglobulin-like receptor subfamily B member 1 (LILRB1) receptors. The downregulated cytotoxic activity of NK cells may be due to inhibitory cytokines present in the peritoneal milieu of patients with endometriosis. The role of NK cell receptors and their ligands in endometriosis is also confirmed by genetic association studies. Thus, endometriosis may be a subject of immunotherapy by blocking NK cell negative control checkpoints including inhibitory NK cell receptors. Immunotherapies with genetically modified NK cells also cannot be excluded.

Morphometric image analysis of placental C-type lectin domain family 2, member D (CLEC2D) immuno-expression in HIV associated pre-eclampsia

OBJECTIVE

C-type lectin domain family 2, member D (CLEC2D) is implicated in the immune response. Pre-eclampsia and HIV infection have opposing immune responses. In view of the high prevalence of HIV infection and pre-eclampsia in South Africa, this study assessed the placental immuno-expression of CLEC2D in HIV associated pre-eclampsia.

METHOD

Placental tissue was obtained from 60 pregnancies which were categorized according to pregnancy type (pre-eclamptic or normotensive) and HIV status (positive or negative). Immunohistochemistry and morphometric image analysis were used to evaluate placental CLEC2D immuno-expression.

RESULTS

CLEC2D expression was significantly decreased in the conducting villi of pre-eclamptic vs normotensive placentae (p = 0.0418) but was increased in the exchange villi, albeit non-significant (p = 0.4948). HIV positive status intensified placental CLEC2D immuno-expression in conducting (p = 0.0312) and exchange (p = 0.0025) villi. CLEC2D expression was significantly different in exchange vs conducting villi (p < 0.0001) and across study groups (p = 0.0003). Normotensive; HIV negative placentae (control) had a non-significant difference in CLEC2D expression across villi types, however significant difference was noted within the remaining groups: normotensive; HIV positive (p < 0.05), pre-eclamptic; HIV positive (p < 0.01 and pre-eclamptic; HIV negative (p < 0.001).

CONCLUSION

The contrasting expression of CLEC2D in HIV infection and pre-eclampsia is demonstrative of the immunosuppressive and pro-inflammatory roles of the respective pathologies. However, this implication may be confounded by highly active anti-retroviral treatment (HAART).

Histidine-rich glycoprotein augments natural killer cell function by modulating PD-1 expression via CLEC-1B

Augmentation of natural killer (NK) cell cytotoxicity is one of the greatest challenges for cancer immunotherapy. Although histidine-rich glycoprotein (HRG), a 75-kDa glycoprotein with various immunomodulatory activities, reportedly elicits antitumor immunity, its effect on NK cell cytotoxicity is unclear. We assessed NK cell cytotoxicity against K562 cells. We also measured concentrations of cytokines and granzyme B in the cell supernatant. The proportion of CD56bright NK cells and NK cell surface PD-1 expression was assessed with flow cytometry. The neutralizing effects of anti-C-type lectin-like receptor (CLEC) 1B against HRG were also measured. NK cell morphological changes were analyzed via confocal microscopy. HRG significantly increased NK cell cytotoxicity against K562 cell lines. HRG also increased the release of granzyme B and the proportion of CD56bright NK cells. Further, HRG was able to decrease NK cell surface PD-1 expression. The effects of HRG on NK cells were reversed with anti-CLEC-1B antibodies. Additionally, we confirmed NK cell nuclear morphology and F-actin distribution, which are involved in the regulation of cytotoxic granule secretion. Because both PD-1 and CLEC-1B are associated with prognosis during malignancy, HRG incorporates these molecules to exert the antitumor immunity role. These facts indicate the potential of HRG to be a new target for cancer immunotherapy.

The killer cell lectin-like receptor B1 (KLRB1) 503T>C polymorphism (rs1135816) and acute rejection after liver transplantation

The killer cell lectin-like receptor B1 (KLRB1) gene encodes for CD161 expressed by different subsets of leukocytes involved in the development of acute liver transplant rejection. The single nucleotide polymorphism (SNP) 503T>C (rs1135816) in the KLRB1 gene represents a missense mutation modifying functional properties of CD161. The aim of our study is to determine whether the SNP 503T>C is associated with acute liver transplant rejection. We genotyped the SNP for 163 liver recipients without acute rejection, 125 recipients with a single acute rejection, and 53 recipients with multiple acute rejections. The genotype frequencies within the groups did not show any significant difference. Our data suggest that the SNP 503T>C has no impact on the susceptibility of acute liver transplant rejection.

Effect of Age on NK Cell Compartment in Chronic Myeloid Leukemia Patients Treated With Tyrosine Kinase Inhibitors

Natural killer (NK) cells are a very important component of the innate immune response involved in the lysis of virus infected and tumor cells. Aging has a profound impact in the frequency, phenotype and function of NK cells. Chronic Myeloid Leukemia (CML) is caused by the BCR-ABL gene formation encoding aberrant oncoprotein tyrosine kinase. Treatment with tyrosine kinase inhibitors (TKIs) induces durable deep molecular response. The response to treatment and life expectancy is lower in older patients with chronic phase of CML than in younger patients. In this work we analyse NK cells from TKI-treated CML patients and healthy controls stratified according to age. We have analyzed the expression of NK receptors, activation markers, NK cell differentiation in CD56^bright and CD56^dim NK cell subsets and the expression of CD107a and IFN-γ in NK cells stimulated with K562. Whereas significant differences on the phenotype and function of NK cells were found between middle-aged (35–65 years old) and elderly (older than 65) healthy individuals, NK cells from TKI-treated CML patients do not show significant differences related with age in most parameters studied, indicating that age is not a limitation of the NK cell recovery after treatment with TKI. Our results also revealed differences in the expression of NK receptors, activation markers and functional assays in NK cells from TKI-treated CML patients compared with age-matched healthy controls. These results highlight the relevance of NK cells in TKI-treated patients and the need of an extensive analysis of the effect of aging on NK cell phenotype and function in these patients in order to define new NK-cell based strategies directed to control CML progression and achieve long-term disease remission after TKI cessation.

NK1.1 Expression Defines a Population of CD4+ Effector T Cells Displaying Th1 and Tfh Cell Properties That Support Early Antibody Production During Plasmodium yoelii Infection

Early plasmablast induction is a hallmark of Plasmodium infection and is thought to contribute to the control of acute parasite burden. Although long understood to be a T-cell dependent phenomenon, regulation of early plasmablast differentiation, however, is poorly understood. Here, we identify a population of CD4⁺ T cells that express the innate NK cell marker NK1.1 as an important source of T cell help for early plasmablast and parasite-specific Ab production. Interestingly, NK1.1⁺ CD4⁺ T cells arise from conventional, naive NK1.1⁻ CD4⁺ T cells, and their generation is independent of CD1d but critically reliant on MHC-II. CD4⁺ T cells that express NK1.1 early after activation produce IFN-γ and IL-21, and express the follicular helper T (Tfh) cell markers ICOS, PD-1 and CXCR5 more frequently than NK1.1⁻ CD4⁺ T cells. Further analysis of this population revealed that NK1.1⁺ Tfh-like cells were more regularly complexed with plasmablasts than NK1.1⁻ Tfh-like cells. Ultimately, depletion of NK1.1⁺ cells impaired class-switched parasite-specific antibody production during early Plasmodium yoelii infection. Together, these data suggest that expression of NK1.1 defines a population of rapidly expanding effector CD4⁺ T cells that specifically promote plasmablast induction during Plasmodium infection and represent a subset of T cells whose modulation could promote effective vaccine design.

Cellular Mechanisms Controlling Surfacing of AICL Glycoproteins, Cognate Ligands of the Activating NK Receptor NKp80

AICL glycoproteins are cognate activation-induced ligands of the C-type lectin-like receptor NKp80, which is expressed on virtually all mature human NK cells, and NKp80-AICL interaction stimulates NK cell effector functions such as cytotoxicity and cytokine secretion. Notably, AICL and NKp80 are encoded by adjacent genes in the NK gene complex and are coexpressed by human NK cells. Whereas AICL is intracellularly retained in resting NK cells, exposure of NK cells to proinflammatory cytokines results in AICL surfacing and susceptibility to NKp80-mediated NK fratricide. In this study, we characterize molecular determinants of AICL glycoproteins that cause intracellular retention, thereby controlling AICL surface expression. Cys⁸⁷ residing within the C-type lectin-like domain not only ensures stable homodimerization of AICL glycoproteins by disulfide bonding, but Cys⁸⁷ is also required for efficient cell surface expression of AICL homodimers and essential for AICL-NKp80 interaction. In contrast, cytoplasmic lysines act as negative regulators targeting AICL for proteasomal degradation. One atypical and three conventional N-linked glycosylation sites in the AICL C-type lectin-like domain critically impact maturation and surfacing of AICL, which is strictly dependent on glycosylation of at least one conventional glycosylation site. However, although the extent of conventional N-linked glycosylation positively correlates with AICL surface expression, the atypical glycosylation site impairs AICL surfacing. Stringent control of AICL surface expression by glycosylation is reflected by the pronounced interaction of AICL with calnexin and the impaired AICL expression in calnexin-deficient cells. Collectively, our data demonstrate that AICL expression and surfacing are tightly controlled by several independent cellular posttranslational mechanisms.

HemITAM: A single tyrosine motif that packs a punch

Innate immune cells sense danger through a plethora of germline-encoded receptors that recognize pathogen-associated molecular patterns (PAMPs) or cellular molecules that are exposed only by stressed, infected, malignant, or dead cells. Many of these danger-sensing receptors belong to the C-type lectin-like superfamily (CLSF) and therefore are called C-type lectin-like receptors (CTLRs). Certain activating CTLRs, namely, CLEC-2, Dectin-1, DNGR-1, NKp80, and NKp65, which are encoded by genes that are clustered together in a subregion of the mammalian natural killer gene complex (NKC), use a single copy tyrosine signaling module termed the hemi-immunoreceptor tyrosine-based activation motif (hemITAM). These hemITAM-bearing CTLRs are present on myeloid cells and innate lymphocytes and stimulate various functions, such as phagocytosis, cytokine production, and cytotoxicity. Proximal signaling mechanisms involve the tyrosine phosphorylation of the hemITAM and the subsequent activation of the kinase Syk. Signaling and Syk recruitment by the hemITAM appear to be tuned by variable amino acids within or near the hemITAM, which give rise to differences in downstream signaling events and diverging functional outcomes among hemITAM-bearing receptors.

High-level expression and purification of soluble form of human natural killer cell receptor NKR-P1 in HEK293S GnTI- cells

Human natural killer receptor protein 1 (NKR-P1, CD161, gene klrb1) is a C-type lectin-like receptor of natural killer (NK) cells responsible for recognition of its cognate protein ligand lectin-like transcript 1 (LLT1). NKR-P1 is the single human orthologue of the prototypical rodent NKR-P1 receptors. Naturally, human NKR-P1 is expressed on the surface of NK cells, where it serves as inhibitory receptor; and on T and NKT cells functioning as co-stimulatory receptor promoting secretion of IFNγ. Most notably, it is expressed on Th17 and Tc17 lymphocytes where presumably promotes targeting into LLT1 expressing immunologically privileged niches. We tested effect of different protein tags (SUMO, TRX, GST, MsyB) on expression of soluble NKR-P1 in E. coli. Then we optimized the expression construct of soluble NKR-P1 by preparing a library of expression constructs in pOPING vector containing the extracellular lectin-like domain with different length of the putative N-terminal stalk region and tested its expression in Sf9 and HEK293 cells. Finally, a high-level expression of soluble NKR-P1 was achieved by stable expression in suspension-adapted HEK293S GnTI^- cells utilizing pOPINGTTneo expression vector. Purified soluble NKR-P1 is homogeneous, deglycosylatable, crystallizable and monomeric in solution, as shown by size-exclusion chromatography, multi-angle light scattering and analytical ultracentrifugation.

A constant companion: immune recognition and response to cytomegalovirus with aging and implications for immune fitness

Approximately 50% of individuals aged 6-49 years in the United States are infected with cytomegalovirus (CMV), with seroprevalence increasing with age, reaching 85-90% by 75-80 years according to Bate et al. (Clin Infect Dis 50 (11): 1439-1447, 2010) and Pawelec et al. (Curr Opin Immunol 24:507-511, 2012). Following primary infection, CMV establishes lifelong latency with periodic reactivation. Immunocompetent hosts experience largely asymptomatic infection, but CMV can cause serious illness in immunocompromised populations, such as transplant patients and the elderly. Control of CMV requires constant immune surveillance, and recent discoveries suggest this demand alters general features of the immune system in infected individuals. Here, we review recent advances in the understanding of the immune response to CMV and the role of CMV in immune aging and fitness, while highlighting the importance of potential confounding factors that influence CMV studies. Understanding how CMV contributes to shaping "baseline" immunity has important implications for a host's ability to mount effective responses to diverse infections and vaccination.

Regulation of NK Cell Activation and Effector Functions by the IL-12 Family of Cytokines: The Case of IL-27

Natural killer (NK) cells are characterized by their ability to detect and induce apoptosis of susceptible target cells and by secretion of immunoregulatory cytokines such as IFN-γ. Activation of these effector functions is triggered upon recognition of tumor and pathogen (mostly virus)-infected cells and because of a bidirectional cross talk that NK cells establish with other cells of myeloid origin such as dendritic cells (DC) and macrophages. A common characteristic of these myeloid cells is their ability to secrete different members of the IL-12 family of cytokines such as IL-12, IL-23, and IL-27 and cytokines such as IL-15 and IL-18. Although the effect of IL-12, IL-15, and IL-18 has been characterized, the effect of IL-23 and IL-27 on NK cells (especially human) remains ill-defined. Particularly, IL-27 is a cytokine with dual functions as it has been described as pro- and as anti-inflammatory in different experimental settings. Recent evidence indicates that this cytokine indeed promotes human NK cell activation, IFN-γ secretion, NKp46-dependent NK cell-mediated cytotoxicity, and antibody (Ab)-dependent NK cell-mediated cytotoxicity (ADCC) against monoclonal Ab-coated tumor cells. Remarkably, IL-27 also primes NK cells for IL-18 responsiveness, enhancing these functional responses. Consequently, IL-27 acts as a pro-inflammatory cytokine that, in concert with other DC-derived cytokines, hierarchically contributes to NK cells activation and effector functions, which likely contributes to foster the adaptive immune response in different physiopathological conditions.

The Activating C-type Lectin-like Receptor NKp65 Signals through a Hemi-immunoreceptor Tyrosine-based Activation Motif (hemITAM) and Spleen Tyrosine Kinase (Syk)

NKp65 is an activating human C-type lectin-like receptor (CTLR) triggering cellular cytotoxicity and cytokine secretion upon high-affinity interaction with the cognate CTLR keratinocyte-associated C-type lectin (KACL) selectively expressed by human keratinocytes. Previously, we demonstrated that NKp65-mediated cellular cytotoxicity depends on tyrosine 7, located in a cytoplasmic sequence motif of NKp65 resembling a hemi-immunoreceptor tyrosine-based activation motif (hemITAM). HemITAMs have been reported for a few activating myeloid-specific CTLRs, including Dectin-1 and CLEC-2, and consist of a single tyrosine signaling unit preceded by a triacidic motif. Upon receptor engagement, the hemITAM undergoes phosphotyrosinylation and specifically recruits spleen tyrosine kinase (Syk), initiating cellular activation. In this study, we addressed the functionality of the putative hemITAM of NKp65. We show that NKp65 forms homodimers and is phosphorylated at the hemITAM-embedded tyrosine 7 upon engagement by antibodies or KACL homodimers. HemITAM phosphotyrosinylation initiates a signaling pathway involving and depending on Syk, leading to cellular activation and natural killer (NK) cell degranulation. However, although NKp65 utilizes Syk for NK cell activation, a physical association of Syk with the NKp65 hemITAM could not be detected, unlike shown previously for the hemITAM of myeloid CTLR. Failure of NKp65 to recruit Syk is not due to an alteration of the triacidic motif, which rather affects the efficiency of hemITAM phosphotyrosinylation. In summary, NKp65 utilizes a hemITAM-like motif for cellular activation that requires Syk, although Syk appears not to be recruited to NKp65.

Monocyte/Macrophage: NK Cell Cooperation-Old Tools for New Functions

Monocyte/macrophage and natural killer (NK) cells are partners from a phylogenetic standpoint of innate immune system development and its evolutionary progressive interaction with adaptive immunity. The equally conservative ways of development and differentiation of both invertebrate hemocytes and vertebrate macrophages are reviewed. Evolutionary conserved molecules occurring in macrophage receptors and effectors have been inherited by vertebrates after their common ancestor with invertebrates. Cytolytic functions of mammalian NK cells, which are rooted in immune cells of invertebrates, although certain NK cell receptors (NKRs) are mammalian new events, are characterized. Broad heterogeneity of macrophage and NK cell phenotypes that depends on surrounding microenvironment conditions and expression profiles of specific receptors and activation mechanisms of both cell types are discussed. The particular tissue specificity of macrophages and NK cells, as well as their plasticity and mechanisms of their polarization to different functional subtypes have been underlined. The chapter summarized studies revealing the specific molecular mechanisms and regulation of NK cells and macrophages that enable their highly specific cross-cooperation. Attention is given to the evolving role of human monocyte/macrophage and NK cell interaction in pathogenesis of hypersensitivity reaction-based disorders, including autoimmunity, as well as in cancer surveillance and progression.

Clr-a: A Novel Immune-Related C-Type Lectin-like Molecule Exclusively Expressed by Mouse Gut Epithelium

The mouse gut epithelium represents a constitutively challenged environment keeping intestinal commensal microbiota at bay and defending against invading enteric pathogens. The complex immunoregulatory network of the epithelial barrier surveillance also involves NK gene complex (NKC)-encoded C-type lectin-like molecules such as NKG2D and Nkrp1 receptors. To our knowledge, in this study, we report the first characterization of the orphan C-type lectin-like molecule Clr-a encoded by the Clec2e gene in the mouse NKC. Screening of a panel of mouse tissues revealed that Clec2e transcripts are restricted to the gastrointestinal tract. Using Clr-a-specific mAb, we characterize Clr-a as a disulfide-linked homodimeric cell surface glycoprotein. Of note, a substantial fraction of Clr-a molecules are retained intracellularly, and analyses of Clr-a/Clr-f hybrids attribute intracellular retention to both the stalk region and parts of the cytoplasmic domain. Combining quantitative PCR analyses with immunofluorescence studies revealed exclusive expression of Clr-a by intestinal epithelial cells and crypt cells throughout the gut. Challenge with polyinosinic-polycytidylic acid results in a rapid and strong downregulation of intestinal Clr-a expression in contrast to the upregulation of Clr-f, a close relative of Clr-a, that also is specifically expressed by the intestinal epithelium and acts as a ligand of the inhibitory Nkrp1g receptor. Collectively, we characterize expression of the mouse NKC-encoded glycoprotein Clr-a as strictly associated with mouse intestinal epithelium. Downregulation upon polyinosinic-polycytidylic acid challenge and expression by crypt cells clearly distinguish Clr-a from the likewise intestinal epithelium-restricted Clr-f, pointing to a nonredundant function of these highly related C-type lectin-like molecules in the context of intestinal immunosurveillance.

Effect of CMV and Aging on the Differential Expression of CD300a, CD161, T-bet, and Eomes on NK Cell Subsets

Natural killer (NK) cells are innate lymphoid cells involved in the defense against virus-infected cells and tumor cells. NK cell phenotype and function is affected with age and cytomegalovirus (CMV) latent infection. Aging affects the frequency and phenotype of NK cells, and CMV infection also contributes to these alterations. Thus, a reduction of CD56^bright NK cell subpopulation associated with age and an expansion of memory-like NK cells CD56^dimCD57⁺NKG2C⁺ probably related to CMV seropositivity have been described. NK cells express T-bet and Eomes transcription factors that are necessary for the development of NK cells. Here, we analyze the effect of age and CMV seropositivity on the expression of CD300a and CD161 inhibitory receptors, and T-bet and Eomes transcription factors in NK cell subsets defined by the expression of CD56 and CD57. CD300a is expressed by the majority of NK cells. CD56^bright NK cells express higher levels of CD300a than CD56^dim NK cells. An increase in the expression of CD300a was associated with age, whereas a decreased expression of CD161 in CD56^dim NK cells was associated with CMV seropositivity. In CD56^dim NK cells, an increased percentage of CD57⁺CD300a⁺ and a reduction in the percentage of CD161⁺CD300a⁺ cells were found to be associated with CMV seropositivity. Regarding T-bet and Eomes transcription factors, CMV seropositivity was associated with a decrease of T-bet^hi in CD56^dimCD57⁺ NK cells from young individuals, whereas Eomes expression was increased with CMV seropositivity in both CD56^bright and CD56^dimCD57^+/− (from middle age and young individuals, respectively) and was decreased with aging in all NK subsets from the three group of age. In conclusion, CMV infection and age induce significant changes in the expression of CD300a and CD161 in NK cell subsets defined by the expression of CD56 and CD57. T-bet and Eomes are differentially expressed on NK cell subsets, and their expression is affected by CMV latent infection and aging.

Dual effects of testosterone in Behcet's disease: implications for a role in disease pathogenesis

Behcet's disease (BD) exhibits more severe disease course and higher mortality among male patients. However, underlying mechanisms of gender differences in clinical manifestations and disease severity are unclear. The aim of this study was to determine whether testosterone (T) has any role on BD pathogenesis. We studied peripheral blood mononuclear cells (PBMC) and neutrophils of BD patients and controls. Functional assay of neutrophils, cytokine measurements of culture supernatants and gene expressions on both cells were analyzed before and after T incubation. Neutrophils were significantly activated after incubation with T in only BD patients. Incubation with T caused significantly elevated interleukin (IL)-12 and IL-2 in BD. Gene expression of IL-10 was significantly downregulated after incubation with T in BD, especially in male patients. The same difference was observed in IL-10 levels in culture supernatant after T. Baseline TLR4 expression was significantly higher in BD patients compared to healthy donors (HC). Toll-like receptor (TLR) 4 expression on PBMC was significantly elevated in female BD patients. ERAP1 expressions of all patients and controls were decreased under the T effect but it differed significantly between BD vs HC. Baseline IL23R expression was higher in BD males compared with females but the difference disappeared after T. When BD patients were analyzed separately, baseline C-C motif chemokine receptor1 (CCR1), STAT4, TLR4 and KLRC4 expressions were lower in males. Despite immunosuppressive behavior in healthy subjects, T causes neutrophil hyperactivation and TH1 type immune alterations in BD patients. Our results suggest that T may have a role in BD pathogenesis by altering the expression level of IL-10, TLR4, ERAP1, CCR1.

Transcriptome Profiling Reveals Disruption of Innate Immunity in Chronic Heavy Ethanol Consuming Female Rhesus Macaques

It is well established that heavy ethanol consumption interferes with the immune system and inflammatory processes, resulting in increased risk for infectious and chronic diseases. However, these processes have yet to be systematically studied in a dose and sex-dependent manner. In this study, we investigated the impact of chronic heavy ethanol consumption on gene expression using RNA-seq in peripheral blood mononuclear cells isolated from female rhesus macaques with daily consumption of 4% ethanol available 22hr/day for 12 months resulting in average ethanol consumption of 4.3 g/kg/day (considered heavy drinking). Differential gene expression analysis was performed using edgeR and gene enrichment analysis using MetaCore™. We identified 1106 differentially expressed genes, meeting the criterion of ≥ two-fold change and p-value ≤ 0.05 in expression (445 up- and 661 down-regulated). Pathway analysis of the 879 genes with characterized identifiers showed that the most enriched gene ontology processes were "response to wounding", "blood coagulation", "immune system process", and "regulation of signaling". Changes in gene expression were seen despite the lack of differences in the frequency of any major immune cell subtype between ethanol and controls, suggesting that heavy ethanol consumption modulates gene expression at the cellular level rather than altering the distribution of peripheral blood mononuclear cells. Collectively, these observations provide mechanisms to explain the higher incidence of infection, delay in wound healing, and increase in cardiovascular disease seen in subjects with Alcohol use disorder.

NKp80 Defines a Critical Step during Human Natural Killer Cell Development

Human natural killer (NK) cells develop in secondary lymphoid tissues (SLTs) through distinct stages. We identified two SLT lineage (Lin)(-)CD34(-)CD117(+/-)CD94(+)CD16(-) "stage 4" subsets according to expression of the C-type lectin-like surface-activating receptor, NKp80: NKp80(-) (stage "4a") and NKp80(+) (stage "4b"). Whereas stage 4b cells expressed more of the transcription factors T-BET and EOMES, produced interferon-gamma, and were cytotoxic, stage 4a cells expressed more of the transcription factors RORγt and AHR and produced interleukin-22, similar to SLT Lin(-)CD34(-)CD117(+)CD94(-)CD16(-) "stage 3" cells, whose phenotype overlaps with that of group 3 innate lymphoid cells (ILC3s). Co-culture with dendritic cells or transplantation into immunodeficient mice produced mature NK cells from stage 3 and stage 4a populations. These data identify NKp80 as a marker of NK cell maturity in SLTs and support a model of human NK cell development through a stage 4a intermediate with ILC3-associated features.

Selective Amplification of the Genome Surrounding Key Placental Genes in Trophoblast Giant Cells

While most cells maintain a diploid state, polyploid cells exist in many organisms and are particularly prevalent within the mammalian placenta [1], where they can generate more than 900 copies of the genome [2]. Polyploidy is thought to be an efficient method of increasing the content of the genome by avoiding the costly and slow process of cytokinesis [1, 3, 4]. Polyploidy can also affect gene regulation by amplifying a subset of genomic regions required for specific cellular function [1, 3, 4]. This mechanism is found in the fruit fly Drosophila melanogaster, where polyploid ovarian follicle cells amplify genomic regions containing chorion genes, which facilitate secretion of eggshell proteins [5]. Here, we report that genomic amplification also occurs in mammals at selective regions of the genome in parietal trophoblast giant cells (p-TGCs) of the mouse placenta. Using whole-genome sequencing (WGS) and digital droplet PCR (ddPCR) of mouse p-TGCs, we identified five amplified regions, each containing a gene family known to be involved in mammalian placentation: the prolactins (two clusters), serpins, cathepsins, and the natural killer (NK)/C-type lectin (CLEC) complex [6-12]. We report here the first description of amplification at selective genomic regions in mammals and present evidence that this is an important mode of genome regulation in placental TGCs.

The c.503T>C Polymorphism in the Human KLRB1 Gene Alters Ligand Binding and Inhibitory Potential of CD161 Molecules

Studying genetic diversity of immunologically relevant molecules can improve our knowledge on their functional spectrum in normal immune responses and may also uncover a possible role of different variants in diseases. We characterized the c.503T>C polymorphism in the human KLRB1 gene (Killer cell lectin-like receptor, subfamily B, member 1) coding for the cell surface receptor CD161. CD161 is expressed by subsets of CD4⁺ and CD8⁺ T cells and the great majority of CD56⁺ natural killer (NK) cells, acting as inhibitory receptor in the latter population. Genotyping a cohort of 118 healthy individuals revealed 40% TT homozygotes, 46% TC heterozygotes, and 14% carriers of CC. There was no difference in the frequency of CD161 expressing CD4⁺ and CD8⁺ T cells between the different genotypes. However, the frequency of CD161⁺ NK cells was significantly decreased in CC carriers as compared to TT homozygotes. c.503T>C causes an amino acid exchange (p.Ile168Thr) in an extracellular loop of the CD161 receptor, which is regarded to be involved in binding of its ligand Lectin-like transcript 1 (LLT1). Binding studies using soluble LLT1-Fc on 293 transfectants over-expressing CD161 receptors from TT or CC carriers suggested diminished binding to the CC variant. Furthermore, triggering of CD161 either by LLT1 or anti-CD161 antibodies inhibited NK cell activation less effectively in cells from CC individuals than cells from TT carriers. These data suggest that the c.503T>C polymorphism is associated with structural alterations of the CD161 receptor. The regulation of NK cell homeostasis and activation apparently differs between carriers of the CC and TT variant of CD161.