Low-Density Neutrophils in Systemic Lupus Erythematosus

Elevated expression of hsa_circ_0000479 in neutrophils correlates with features of systemic lupus erythematosus

OBJECTIVE

Accumulating evidence suggests that differentially expressed circular RNAs (circRNAs) play critical roles in immune cells of systemic lupus erythematosus (SLE) patients. Hsa_circ_0000479 has been studied in the field of cancer and infection, whereas seldom studied in autoimmune diseases. The aim of this study was to investigate the role and clinical value of neutrophil hsa_circ_0000479 in SLE.

METHODS

The expression levels of hsa_circ_0000479 in both healthy individuals and SLE patients' neutrophils were detected by qPCR and compared with those in peripheral blood mononuclear cells (PBMCs) . In addition, the correlation of hsa_circ_0000479 levels in neutrophils with the clinical and immunological features of SLE patients was also analysed.

RESULTS

The expression levels of hsa_circ_0000479 in the patients with SLE were significantly higher in neutrophils than that of PBMCs, and also significantly higher than that in healthy controls (HCs). Moreover, the expression levels of hsa_circ_0000479 in neutrophils were negatively associated with absolute neutrophil count and complement 3 (C3), whereas positively correlated with anti-dsDNA and anti-nucleosome antibodies in SLE. In addition, SLE patients with higher levels of hsa_circ_0000479 demonstrated more several clinical manifestations, including Raynaud's phenomenon, alopecia and leucopenia.

CONCLUSIONS

Hsa_circ_0000479 is up-regulated in neutrophils of SLE patients, and is also associated with several important laboratory indicators and clinical manifestations, suggesting that hsa_circ_0000479 in neutrophils was one of probable factors involved in the pathogenesis of SLE with potential clinical value.

Systems Immunology Approaches to Understanding Immune Responses in Acute Infection of Yellow Fever Patients

In the 2018 yellow fever (YF) outbreak in Brazil, we generated new transcriptomic data and combined it with clinical and immunological data to decode the pathogenesis of YF. Analyzing 79 patients, we found distinct gene expression patterns between acute YF, other viral infections, and the milder YF-17D vaccine infection. We identified a critical role for low-density, immature neutrophils in severe outcomes, marked by the downregulation of genes essential for neutrophil migration and maturation, such as PADI4, CSF3R, and ICAM1, in deceased patients. Our study also revealed complex interactions among inflammation-related genes, including increased CXCL10 and IL1R2 expression and decreased IL-1b expression in the acute phase. The diminished expression of HLA class II genes indicates impaired antigen presentation. These findings highlight the delicate balance of immune responses in YF pathogenesis and lay the groundwork for future therapeutic and diagnostic advancements.

Comprehensive mapping of immune perturbations associated with secondary hemophagocytic lymphohistiocytosis

Secondary hemophagocytic lymphohistiocytosis (sHLH) is a hyperinflammatory syndrome characterized by immune disorders. It is imperative to elucidate the immunophenotypic panorama and the interactions among these cells in patients. Human peripheral blood mononuclear cells were collected from healthy donors and sHLH patients and tested using multicolor flow cytometry. We used FlowSOM to explore and visualize the immunophenotypic characteristics of sHLH. By demonstrating the phenotypes of immune cells, we discovered that sHLH patients had significantly higher levels of CD56+ monocytes, higher levels of myeloid-derived suppressor cells, low-density neutrophil-to-T cell ratio, and higher heterogeneous T cell activation than healthy donors. However, natural killer cell cytotoxicity and function were impaired. We then assessed the correlations among 30 immune cell types and evaluated metabolic analysis. Our findings demonstrated polymorphonuclear myeloid-derived suppressor cells, CD56+ monocytes, and neutrophil-to-T cell ratio were elevated abnormally in sHLH patients, which may indicate an association with immune overactivation and inflammatory response. We are expected to confirm that they are involved in the occurrence of the disease through further in-depth research.

Extracellular traps in peripheral blood mononuclear cell fraction in childhood-onset systemic lupus erythematosus

Although the role of low-density granulocytes (LDGs), neutrophils in the peripheral blood mononuclear cell (PBMC) fraction, and neutrophil extracellular traps (NETs) in assessing lupus disease severity is acknowledged, data specific to childhood-onset lupus remains scarce. This study analyzed 46 patients with childhood-onset systemic lupus erythematosus (82.6% females, mean age 14.5 ± 0.3 years), including 26 cases with normal complement levels and 20 with low complement levels, along with 20 healthy adult volunteers. Key parameters that distinguished healthy volunteers from lupus patients and differentiated between lupus patients with low and normal complement were serum interferon (IFN)-α, serum citrullinated histone 3 (CitH3), and extracellular traps (ETs) in LDGs. However, NETs (assessed by nuclear staining morphology), LDG abundance, and other parameters (such as endotoxemia, cytokines, and double-stranded (ds) DNA) did not show such differentiation. When lipopolysaccharide (LPS) was administered to LDGs in the PBMC fraction, it induced ETs in both low and normal complement groups, indicating the inducible nature of ETs. In adult healthy volunteers, activation by recombinant IFN-α or dsDNA in isolated neutrophils induced LDGs and NETs (identified using immunofluorescent staining for CitH3, myeloperoxidase, and neutrophil elastase) at 45 min and 3 h post-stimulation, respectively. Additionally, approximately half of the LDGs underwent late apoptosis at 3 h post-stimulation, as determined by flow cytometry analysis. Activation by IFN-α or dsDNA in LDGs also led to a more pronounced expression of CD66b, an adhesion molecule, compared to regular-density neutrophils, suggesting higher activity in LDGs. In conclusion, IFN-α and/or dsDNA in serum may transform regular-density neutrophils into LDGs before progressing to NETosis and apoptosis, potentially exacerbating lupus severity through cell death-induced self-antigens. Therefore, LDGs and ETs in LDGs could provide deeper insights into the pathophysiology of childhood-onset lupus.

Neutrophils-biology and diversity

Neutrophils, the most abundant white blood cells in the human circulation, play crucial roles in various diseases, including kidney disease. Traditionally viewed as short-lived pro-inflammatory phagocytes that release reactive oxygen species, cytokines and neutrophil extracellular traps, recent studies have revealed their complexity and heterogeneity, thereby challenging this perception. Neutrophils are now recognized as transcriptionally active cells capable of proliferation and reverse migration, displaying phenotypic and functional heterogeneity. They respond to a wide range of signals and deploy various cargo to influence the activity of other cells in the circulation and in tissues. They can regulate the behavior of multiple immune cell types, exhibit innate immune memory, and contribute to both acute and chronic inflammatory responses while also promoting inflammation resolution in a context-dependent manner. Here, we explore the origin and heterogeneity of neutrophils, their functional diversity, and the cues that regulate their effector functions. We also examine their emerging role in infectious and non-infectious diseases with a particular emphasis on kidney disease. Understanding the complex behavior of neutrophils during tissue injury and inflammation may provide novel insights, thereby paving the way for potential therapeutic strategies to manage acute and chronic conditions. By deciphering their multifaceted role, targeted interventions can be developed to address the intricacies of neutrophil-mediated immune responses and improve disease outcomes.

Neutrophil extracellular traps in homeostasis and disease

Neutrophil extracellular traps (NETs), crucial in immune defense mechanisms, are renowned for their propensity to expel decondensed chromatin embedded with inflammatory proteins. Our comprehension of NETs in pathogen clearance, immune regulation and disease pathogenesis, has grown significantly in recent years. NETs are not only pivotal in the context of infections but also exhibit significant involvement in sterile inflammation. Evidence suggests that excessive accumulation of NETs can result in vessel occlusion, tissue damage, and prolonged inflammatory responses, thereby contributing to the progression and exacerbation of various pathological states. Nevertheless, NETs exhibit dual functionalities in certain pathological contexts. While NETs may act as autoantigens, aggregated NET complexes can function as inflammatory mediators by degrading proinflammatory cytokines and chemokines. The delineation of molecules and signaling pathways governing NET formation aids in refining our appreciation of NETs' role in immune homeostasis, inflammation, autoimmune diseases, metabolic dysregulation, and cancer. In this comprehensive review, we delve into the multifaceted roles of NETs in both homeostasis and disease, whilst discussing their potential as therapeutic targets. Our aim is to enhance the understanding of the intricate functions of NETs across the spectrum from physiology to pathology.

Comprehensive mapping of immune perturbations associated with aplastic anemia

BACKGROUND

Aplastic anemia (AA) is an immune-mediated syndrome characterized by bone marrow failure. Therefore, comprehending the cellular profile and cell interactions in affected patients is crucial.

METHODS

Human peripheral blood mononuclear cells (PBMCs) were collected from both healthy donors (HDs) and AA patients, and analyzed using multicolor flow cytometry. Utilizing the FlowSOM and t-SNE dimensionality reduction technique, we systematically explored and visualized the major immune cell alterations in AA. This analysis provided a foundation to further investigate the subtypes of cells exhibiting significant changes.

RESULTS

Compared to HDs, peripheral blood from patients with AA exhibits a marked reduction in CD56Dim natural killer (NK) cells, which also show diminished functionality. Conversely, an increase in NK-like CD56+ monocytes, which possess compromised functionality. Along with a significant reduction in myeloid-derived suppressor cells (MDSCs), which show recovery post-treatment. Additionally, MDSCs serve as effective clinical markers for distinguishing between acquired aplastic anemia (AAA) and congenital aplastic anemia (CAA). Our comprehensive analysis of correlations among distinct immune cell types revealed significant associations between NKBri cells and CD8+ T cell subsets, as well as between NKDim cells and CD4+ T cells, these results highlight the intricate interactions and correlations within the immune cell network in AA.

CONCLUSION

Our study systematically elucidates the pronounced immune dysregulation in patients with AA. The detailed mapping of the immune landscape not only provides crucial insights for basic research but also holds promise for enhancing the accuracy of diagnoses and the effectiveness of timely therapeutic interventions in clinical practice. Consequently, this could potentially reduce the high mortality rate associated with AA.

Integrative profiling of untreated primary membranous nephropathy at the single-cell transcriptome level

Background

Primary membranous nephropathy (PMN) is an autoimmune kidney disease. Despite the identification of certain autoantigens, the etiology and pathophysiology of PMN are still largely unknown.

Methods

Five patients with biopsy-proven PMN were enrolled in this study. Their blood, kidney and urine samples were collected respectively to profile cellular, molecular and immunological alterations by using single-cell RNA sequencing (scRNA-seq). Experimental verifications were also implemented in kidney tissue.

Results

In the peripheral blood mononuclear cell (PBMC) samples, portions of B cells and plasma cells were increased in PMN patients. Cell-cell communication analysis suggests that APRIL (a proliferation-inducing ligand from B cells) might be a potential molecule that regulates the activity of plasma cells. In the kidney samples, scRNA-seq analysis showed that the infiltration of T cells, as well as the myeloid cells, appears abundant compared with healthy controls, suggesting that immune cells are actively recruited to kidney. Furthermore, we observed an enhanced interaction between inflammatory cells and podocytes, which might contribute to kidney injury. Accordingly, scRNA-seq analysis of urinary samples is partially reminiscent of the kidney cell landscape, especially T cells and myeloid cells, suggesting monitoring urinary samples is a promising method to monitor PMN development. Additionally, integrative analysis across the blood, kidney and urine identified LTB, HERP1, ANXA1, IL1RN and ICAM1 as common regulators of PMN. Finally, immune repertoire in PBMC also showed an elevated diversity of clonal type, implying the existence of autoreactive T-cell receptor/B-cell receptor.

Conclusion

Our study comprehensively profiled the transcriptomic landscapes of blood, kidney and urine in patients with PMN using scRNA-seq. We depicted the alterations including cell compositions and cell-cell communication in PMN. These results offer important clues with regard to the diagnosis and pathogenesis of PMN and potential intervention of PMN progression.

Abnormal energy metabolism in the pathogenesis of systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a severe autoimmune disease with significant socioeconomic impact worldwide. Orderly energy metabolism is essential for normal immune function, and disordered energy metabolism is increasingly recognized as an important contributor to the pathogenesis of SLE. Disorders of energy metabolism are characterized by increased reactive oxygen species, ATP deficiency, and abnormal metabolic pathways. Oxygen and mitochondria are critical for the production of ATP, and both mitochondrial dysfunction and hypoxia affect the energy production processes. In addition, several signaling pathways, including mammalian target of rapamycin (mTOR)/adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK) signaling and the hypoxia-inducible factor (HIF) pathway also play important regulatory roles in energy metabolism. Furthermore, drugs with clear clinical effects on SLE, such as sirolimus, metformin, and tacrolimus, have been proven to improve the disordered energy metabolism of immune cells, suggesting the potential of targeting energy metabolism for the treatment of SLE. Moreover, several metabolic modulators under investigation are expected to have potential therapeutic effects in SLE. This review aimed to gain insights into the role and mechanism of abnormal energy metabolism in the pathogenesis of SLE, and summarizes the progression of metabolic modulator in the treatment of SLE.

Neutrophils cultured ex vivo from CD34+ stem cells are immature and genetically tractable

BACKGROUND

Neutrophils are granulocytes with essential antimicrobial effector functions and short lifespans. During infection or sterile inflammation, emergency granulopoiesis leads to release of immature neutrophils from the bone marrow, serving to boost circulating neutrophil counts. Steady state and emergency granulopoiesis are incompletely understood, partly due to a lack of genetically amenable models of neutrophil development.

METHODS

We optimised a method for ex vivo production of human neutrophils from CD34+ haematopoietic progenitors. Using flow cytometry, we phenotypically compared cultured neutrophils with native neutrophils from donors experiencing emergency granulopoiesis, and steady state neutrophils from non-challenged donors. We carry out functional and proteomic characterisation of cultured neutrophils and establish genome editing of progenitors.

RESULTS

We obtain high yields of ex vivo cultured neutrophils, which phenotypically resemble immature neutrophils released into the circulation during emergency granulopoiesis. Cultured neutrophils have similar rates of ROS production and bacterial killing but altered degranulation, cytokine release and antifungal activity compared to mature neutrophils isolated from peripheral blood. These differences are likely due to incomplete synthesis of granule proteins, as demonstrated by proteomic analysis.

CONCLUSION

Ex vivo cultured neutrophils are genetically tractable via genome editing of precursors and provide a powerful model system for investigating the properties and behaviour of immature neutrophils.

Immature neutrophils in cord blood exert increased expression of genes associated with antimicrobial function

Introduction

The immune systems of both the mother and the newborn face significant challenges during birth. Proper immune regulation after birth is essential for the survival of neonates. Numerous studies have demonstrated that the neonatal immune system is relatively immature, particularly in its adaptive arm, placing the primary responsibility for immune surveillance on innate immunity.

Methods

Given the significant role of neutrophils in protecting the neonate after birth, we conducted a study investigating the properties of neutrophils in newborn cord blood using various methodological approaches.

Results

Our findings demonstrate the presence of immature low-density neutrophils in the cord blood, which are likely responsible for the observed elevated expression of genes coding for proteins essential to antimicrobial response, including myeloperoxidase, neutrophils elastase, and defensins.

Discussion

We propose that these cells function normally and support the protection of newborns early after birth. Furthermore, our results suggest that the mode of delivery might significantly influence the programming of neutrophil function. The presented findings emphasize the importance of distinct neutrophil subpopulations in neonatal immunity and their potential impact on early postnatal health.

Phenotype and oxidative burst of low-density neutrophil subpopulations are altered in common variable immunodeficiency patients

Common variable immunodeficiency disorder (CVID) is the most common form of primary antibody immunodeficiency. Due to low antibody levels, CVID patients receive intravenous or subcutaneous immunoglobulin replacement therapy as treatment. CVID is associated with the chronic activation of granulocytes, including an increased percentage of low-density neutrophils (LDNs). In this study, we examined changes in the percentage of LDNs and the expression of their surface markers in 25 patients with CVID and 27 healthy donors (HD) after in vitro stimulation of whole blood using IVIg. An oxidative burst assay was used to assess the functionality of LDNs. CVID patients had increased both relative and absolute LDN counts with a higher proportion of mLDNs compared to iLDNs, distinguished based on the expression of CD10 and CD16. Immature LDNs in the CVID and HD groups had significantly reduced oxidative burst capacity compared to mature LDNs. Interestingly we observed reduced oxidative burst capacity, reduced expression of CD10 after stimulation of WB, and higher expression of PD-L1 in mature LDNs in CVID patients compared to HD cells. Our data indicate that that the functional characteristics of LDNs are closely linked to their developmental stage. The observed reduction in oxidative burst capacity in mLDNs in CVID patients could contribute to an increased susceptibility to recurrent bacterial infections among CVID patients.

Platelet TLR7 is essential for the formation of platelet-neutrophil complexes and low-density neutrophils in lupus nephritis

OBJECTIVES

Platelets and low-density neutrophils (LDNs) are major players in the immunopathogenesis of SLE. Despite evidence showing the importance of platelet-neutrophil complexes (PNCs) in inflammation, little is known about the relationship between LDNs and platelets in SLE. We sought to characterize the role of LDNs and Toll-like receptor 7 (TLR7) in clinical disease.

METHODS

Flow cytometry was used to immunophenotype LDNs from SLE patients and controls. The association of LDNs with organ damage was investigated in a cohort of 290 SLE patients. TLR7 mRNA expression was assessed in LDNs and high-density neutrophils (HDNs) using publicly available mRNA sequencing datasets and our own cohort using RT-PCR. The role of TLR7 in platelet binding was evaluated in platelet-HDN mixing studies using TLR7-deficient mice and Klinefelter syndrome patients.

RESULTS

SLE patients with active disease have more LDNs, which are heterogeneous and more immature in patients with evidence of kidney dysfunction. LDNs are platelet bound, in contrast to HDNs. LDNs settle in the peripheral blood mononuclear cell (PBMC) layer due to the increased buoyancy and neutrophil degranulation from platelet binding. Mixing studies demonstrated that this PNC formation was dependent on platelet-TLR7 and that the association results in increased NETosis. The neutrophil:platelet ratio is a useful clinical correlate for LDNs, and a higher NPR is associated with past and current flares of LN.

CONCLUSIONS

LDNs sediment in the upper PBMC fraction due to PNC formation, which is dependent on the expression of TLR7 in platelets. Collectively, our results reveal a novel TLR7-dependent crosstalk between platelets and neutrophils that may be an important therapeutic opportunity for LN.

The Role of Neutrophil in COVID-19: Positive or Negative

BACKGROUND

Neutrophils are the first line of defense against pathogens. They are divided into multiple subpopulations during development and kill pathogens through various mechanisms. Neutrophils are considered one of the markers of severe COVID-19.

SUMMARY

In-depth research has revealed that neutrophil subpopulations have multiple complex functions. Different subsets of neutrophils play an important role in the progression of COVID-19.

KEY MESSAGES

In this review, we provide a detailed overview of the developmental processes of neutrophils at different stages and their recruitment and activation after SARS-CoV-2 infection, aiming to elucidate the changes in neutrophil subpopulations, characteristics, and functions after infection and provide a reference for mechanistic research on neutrophil subpopulations in the context of SARS-CoV-2 infection. In addition, we have also summarized research progress on potential targeted drugs for neutrophil immunotherapy, hoping to provide information that aids the development of therapeutic drugs for the clinical treatment of critically ill COVID-19 patients.

The activation of SIRT1 by resveratrol reduces breast cancer metastasis to lung through inhibiting neutrophil extracellular traps

Neutrophil extracellular traps (NETs) play a crucial role in breast cancer metastasis. However, the therapeutic target of NETs in breast cancer metastasis is still unknown. Using a natural metabolite library and single-cell sequencing data analysis, we identified resveratrol (RES), a polyphenolic natural phytoalexin, and agonist of silent information regulator-1 (SIRT1) that suppressed NETs formation after cathepsin C (CTSC) treatment. In vivo, RES significantly hindered breast cancer metastasis in a murine orthotopic 4T1 breast cancer model. Serum levels of myeloperoxidase-DNA and neutrophil elastase-DNA in mouse breast cancer model were significantly lower after RES treatment. Correspondingly, the tumour infiltrated CD8+T cells in the lungs increased after the treatment. Mechanistically, RES targets SIRT1 in neutrophils and significantly inhibits the citrullination of histones H3, which is essential for chromatin decondensation and NETs formation. Furthermore, we identified that the NETs were suppressed by RES in bone marrow neutrophils after CTSC treatment, while specific deficiency of SIRT1 in neutrophils promoted NETs formation and breast cancer to lung metastasis. Thus, our results revealed that RES could be potentially identified as a viable therapeutic drug to prevent neutrophil cell death and breast cancer metastasis.

Neutrophil heterogeneity and aging: implications for COVID-19 and wound healing

Neutrophils play a critical role in the immune response to infection and tissue injury. However, recent studies have shown that neutrophils are a heterogeneous population with distinct subtypes that differ in their functional properties. Moreover, aging can alter neutrophil function and exacerbate immune dysregulation. In this review, we discuss the concept of neutrophil heterogeneity and how it may be affected by aging. We then examine the implications of neutrophil heterogeneity and aging for COVID-19 pathogenesis and wound healing. Specifically, we summarize the evidence for neutrophil involvement in COVID-19 and the potential mechanisms underlying neutrophil recruitment and activation in this disease. We also review the literature on the role of neutrophils in the wound healing process and how aging and neutrophil heterogeneity may impact wound healing outcomes. Finally, we discuss the potential for neutrophil-targeted therapies to improve clinical outcomes in COVID-19 and wound healing.

Single-cell transcriptomics reveals peripheral immune responses in non-segmental vitiligo

Background

Vitiligo is a common autoimmune depigmented dermatology due to destruction of melanocytes. Much evidence suggests that vitiligo is associated with systemic immune activation. Previous studies have focused on immune cell infiltration in and around lesion areas, but few studies have investigated the cell types and function of circulating immune cells in peripheral blood. Here, single cell RNA-sequencing (scRNA-seq) was used to investigate the mechanisms of peripheral immune responses in vitiligo patients.

Methods

Peripheral blood was collected from five patients with progressive non-segmental vitiligo and three healthy controls. Peripheral blood mononuclear cells (PBMCs) were obtained by Ficoll-Paque density gradient centrifugation, and scRNA-seq was performed on isolated cell populations to obtain single cell transcriptomes and characterize important genes and intracellular signaling pathways. The key findings were validated with qPCR and flow cytometry assays.

Results

We identified 10 major cell types by scRNA-seq. Among these cell types, neutrophils were specifically observed in our scRNA-seq data from PBMCs. Peripheral blood effector CD8+ T cells from vitiligo patients did not show significant differences at the transcriptome level compared with healthy controls, whereas regulatory T cells showed pro-inflammatory TH1-like properties. Innate immune cells, including natural killer cells and dendritic cells, showed increased antigen processing and presentation as well as upregulated interferon responses. B cells, monocytes, and neutrophils all showed activation. B cells, especially memory B cells, had upregulated expression of genes related to humoral immunity. Monocytes showed production of proinflammatory cytokines and chemokines. Neutrophils showed strong chemokine ligand-receptor (L-R) pair (CXCR8-CXCR2) autocrine signaling pathway.

Conclusion

This study revealed the genetic profile and signaling pathway characteristics of peripheral blood immune cells in vitiligo patients, providing new insights into its pathogenesis, which may facilitate identification of potential therapeutic targets.

Mitophagy-related genes could facilitate the development of septic shock during immune infiltration

Septic shock often occurs following critically low blood pressure in patients with sepsis, and is accompanied by a high death rate. Although mitophagy is associated with infection and immune responses, its role in septic shock remains unknown. This study screened effective mitophagy-related genes (MRGs) for medical practice and depicted immune infiltration situations in patients with septic shock. Gene expression profiles of GSE131761 from the Gene Expression Omnibus database were compiled for differential analysis, weighted gene co-expression network analysis, and immune infiltration analysis, while other GSE series were used as validation datasets. A series of validation methods were used to verify the robustness of hub genes, while a nomogram and prognosis model were established for medical practice. Six genes were screened via combinations of differentially expressed genes, weighted gene co-expression network analysis, and MRGs. From this, 3 hub genes (MAP1LC3B, ULK1, and CDC37) were chosen for subsequent analysis based on different validation methods. Gene set enrichment analysis showed that leukocyte trans-endothelial migration and the p53 signaling pathway were abnormally activated during septic shock. Immune infiltration analysis indicated that the imbalance of neutrophils and CD4 naive T cells was significantly correlated with septic shock progression. A nomogram was generated based on MAP1LC3B, ULK1, and CDC37, as well as age. The stability of our model was confirmed using a calibration plot. Importantly, patients with septic shock with the 3 highly expressed hub genes displayed worse prognosis than did patients without septic shock. MAP1LC3B, ULK1, and CDC37 are considered hub MRGs in the development of septic shock and could represent promising diagnostic and prognostic biomarkers in blood tissue. The validated hub genes and immune infiltration pattern expand our knowledge on MRG functional mechanisms, which provides guidance and direction for the development of septic shock diagnostic and therapeutic markers.

Proteomic analyses reveal cystatin c is a promising biomarker for evaluation of systemic lupus erythematosus

BACKGROUND

Systemic lupus erythematosus (SLE) is an autoimmune disease with multiple organ involvement, especially the kidneys. However, the underlying mechanism remains unclear, and accurate biomarkers are still lacking. This study aimed to identify biomarkers to assess organ damage and disease activity in patients with SLE using quantitative proteomics.

METHODS

Proteomic analysis was performed using mass spectrometry in 15 patients with SLE and 15 age-matched healthy controls. Proteomic profiles were compared in four main subtypes: SLE with proteinuria (SLE-PN), SLE without proteinuria (SLE-non-PN), SLE with anti-dsDNA positivity (SLE-DP), and SLE with anti-dsDNA negativity (SLE-non-DP). Gene ontology biological process analysis revealed differentially expressed protein networks. Cystatin C (CysC) levels were measured in 200 patients with SLE using an immunoturbidimetric assay. Clinical and laboratory data were collected to assess their correlation with serum CysC levels.

RESULTS

Proteomic analysis showed that upregulated proteins in both the SLE-PN and SLE-DP groups were mainly mapped to neutrophil activation networks. Moreover, CysC from neutrophil activation networks was upregulated in both the SLE-PN and SLE-DP groups. The associations of serum CysC level with proteinuria, anti-dsDNA positivity, lower complement C3 levels, and SLE disease activity index score in patients with SLE were further validated in a large independent cohort.

CONCLUSIONS

Neutrophil activation is more prominent in SLE with proteinuria and anti-dsDNA positivity, and CysC is a promising marker for monitoring organ damage and disease activity in SLE.

Neutrophil subsets in noncancer liver diseases: Cellular crosstalk and therapeutic targets

Neutrophils are the most abundant circulating granulocytes, linking innate and adaptive immunity. Neutrophils can regulate inflammatory and immune responses through degranulation, reactive oxygen species generation, the production of cytokines and chemokines, and NETosis. Emerging evidence has indicated that neutrophils contribute to the pathogenesis of various noncancer liver diseases, including nonalcoholic fatty liver disease, alcohol-associated liver disease, hepatic ischemia-reperfusion injury, and liver fibrosis. Cellular interactions among neutrophils, other immune cells, and nonimmune cells constitute a complex network that regulates the immune microenvironment of the liver. This review summarizes novel neutrophil subtypes, including CD177+ neutrophils and low-density neutrophils. Moreover, we provide an overview of the cellular cros stalk of neutrophils in noncancer liver diseases, aiming to shed new light on mechanistic studies of novel neutrophil subtypes. In addition, we discuss the potential of neutrophils as therapeutic targets in noncancer liver diseases, including inhibitors targeting NETosis, granule proteins, and chemokines.

Th17/Treg balance is regulated by myeloid-derived suppressor cells in experimental autoimmune myocarditis

OBJECTIVE

Autoimmune myocarditis is caused by both innate and adaptive immune responses. Many studies have found that myeloid-derived suppressor cells (MDSCs) suppress T-cell responses and reduce immune tolerance, while MDSCs may serve as a key player in inflammatory responses and pathogenesis in variety of autoimmune diseases. However, research into the role of MDSCs in experimental autoimmune myocarditis (EAM) remains lacking.

METHODS AND RESULTS

We discovered that the expansion of MDSCs in EAM was closely related to the severity of myocardial inflammation. At an early stage of EAM, both adoptive transfer (AT) and selective depletion of MDSCs could inhibit the expression of IL-17 in CD4+ cells and downregulate the Th17/Treg ratio, alleviating excessive inflammation of EAM myocarditis. In another experiment, in addition, MDSCs transferred after selective depletion could increase IL-17 and Foxp3 expressions in CD4+ cells, as well as the Th17/Treg ratio, contributing to the aggravation of myocardial inflammation. MDSCs promoted the Th17 cell induction under Th17-polarizing conditions in vitro but suppressed Treg expansion.

CONCLUSION

These findings suggest that MDSCs play a plastic role in sustaining mild inflammation in EAM by shifting Th17/Treg balance.

Pathogenic cellular and molecular mediators in lupus nephritis

Kidney involvement in patients with systemic lupus erythematosus - lupus nephritis (LN) - is one of the most important and common clinical manifestations of this disease and occurs in 40-60% of patients. Current treatment regimens achieve a complete kidney response in only a minority of affected individuals, and 10-15% of patients with LN develop kidney failure, with its attendant morbidity and considerable prognostic implications. Moreover, the medications most often used to treat LN - corticosteroids in combination with immunosuppressive or cytotoxic drugs - are associated with substantial side effects. Advances in proteomics, flow cytometry and RNA sequencing have led to important new insights into immune cells, molecules and mechanistic pathways that are instrumental in the pathogenesis of LN. These insights, together with a renewed focus on the study of human LN kidney tissue, suggest new therapeutic targets that are already being tested in lupus animal models and early-phase clinical trials and, as such, are hoped to eventually lead to meaningful improvements in the care of patients with systemic lupus erythematosus-associated kidney disease.

Neutrophil interactions with T cells, platelets, endothelial cells, and of course tumor cells

Neutrophils sense microbes and host inflammatory mediators, and traffic to sites of infection where they direct a broad armamentarium of antimicrobial products against pathogens. Neutrophils are also activated by damage-associated molecular patterns (DAMPs), which are products of cellular injury that stimulate the innate immune system through pathways that are similar to those activated by microbes. Neutrophils and platelets become activated by injury, and cluster and cross-signal to each other with the cumulative effect of driving antimicrobial defense and hemostasis. In addition, neutrophil extracellular traps are extracellular chromatin and granular constituents that are generated in response to microbial and damage motifs and are pro-thrombotic and injurious. Although neutrophils can worsen tissue injury, neutrophils may also have a role in facilitating wound repair following injury. A central theme of this review relates to how critical functions of neutrophils that evolved to respond to infection and damage modulate the tumor microenvironment (TME) in ways that can promote or limit tumor progression. Neutrophils are reprogrammed by the TME, and, in turn, can cross-signal to tumor cells and reshape the immune landscape of tumors. Importantly, promising new therapeutic strategies have been developed to target neutrophil recruitment and function to make cancer immunotherapy more effective.

Neutrophils are gatekeepers of mucosal immunity

Mucosal tissues are constantly exposed to the outside environment. They receive signals from the commensal microbiome and tissue-specific triggers including alimentary and airborne elements and are tasked to maintain balance in the absence of inflammation and infection. Here, we present neutrophils as sentinel cells in mucosal immunity. We discuss the roles of neutrophils in mucosal homeostasis and overview clinical susceptibilities in patients with neutrophil defects. Finally, we present concepts related to specification of neutrophil responses within specific mucosal tissue microenvironments.

Downregulation of miR-137 Facilitates CD4+ T Cell Pyroptosis in Systemic Lupus Erythematosus via Stimulating AMPK Pathway

Objective

From the pathogenic mechanism point of view, systemic lupus erythematosus (SLE) features prominently in T lymphocyte apoptosis. Yet the regulatory mechanism underlying SLE cell apoptosis remains to be explored. This research intends to clarify the role played by miR-137 in SLE and the underlying mechanisms.

Methods

Twenty SLE patients (SLE group) and twenty healthy controls (control group) were selected, from whom peripheral blood CD4+ T cells were isolated via magnetic-activated cell sorting. Reverse transcription-polymerase chain reaction (RT-PCR) quantified miR-137 and AMP-activated protein kinase (AMPK) in CD4+ T cells. Further, transfection of miR-137 mimics and inhibitors into CD4+ T cells was carried out to alter miR levels. Levels of pyroptosis, apoptosis, and inflammatory- and pyroptosis-related proteins were determined through PI staining, flow cytometry, and Western blotting, respectively. A luciferase reporter gene assay identified the targeting relation between miR-137 and AMPK.

Results

SLE patients showed downregulated miR-137 and upregulated AMPK in CD4+ T cells than controls. miR-137 upregulation by miR-137 mimic transfection inhibited Jurkat cell pyroptosis and apoptosis at both mRNA and protein levels and suppressed NOD-like receptor thermal protein domain-associated protein 3 (NLRP3) inflammasome activity and pyroptosis-related protein gasdermin D (GSDMD), while miR-137 inhibitor transfection contributed to completely opposite effects. miR-137 directly targeted AMPK, as indicated by the luciferase reporter gene assay. Furthermore, miR-137 inhibitor intervention induced healthy CD4+ T cell pyroptosis and apoptosis via mediating AMPK, whereas miR-137 mimic transfection into CD4+ T cells of SLE patients leads to opposite results.

Conclusion

Upregulating miR-137 inhibits CD4+ T cell pyroptosis in SLE patients by modulating the AMPK pathway, suggesting the potential diagnostic and therapeutic role of miR-137 in SLE.

High throughput sequencing revealed enhanced cell cycle signaling in SLE patients

The multi-system involvement and high heterogeneity of systemic lupus erythematosus (SLE) pose great challenges to its diagnosis and treatment. The purpose of the current study is to identify genes and pathways involved in the pathogenesis of SLE. High throughput sequencing was performed on the PBMCs from SLE patients. We conducted differential gene analysis, gene ontology (GO) analysis, kyoto encyclopedia of genes and genomes (KEGG) analysis, and quantitative real-time PCR (qRT-PCR) verification. Protein-protein interaction (PPI) analysis, alternative splicing analysis, and disease correlation analysis were conducted on some key pathogenic genes as well. Furthermore, si-CDC6 was used for transfection and cell proliferation was monitored using a cell counting kit-8 (CCK-8) assay. We identified 2495 differential genes (1494 upregulated and 1001 downregulated) in SLE patients compared with healthy controls. The significantly upregulated genes were enriched in the biological process-related GO terms of the cell cycle, response to stress, and chromosome organization. KEGG enrichment analysis revealed 7 significantly upregulated pathways including SLE, alcoholism, viral carcinogenesis, cell cycle, proteasome, malaria, and transcriptional misregulation in cancer. We successfully verified some differential genes on the SLE pathway and the cell cycle pathway. CDC6, a key gene in the cell cycle pathway, had remarkably higher MXE alternative splicing events in SLE patients than that in controls, which may explain its significant upregulation in SLE patients. We found that CDC6 participates in the pathogenesis of many proliferation-related diseases and its levels are positively correlated with the severity of SLE. Knockdown of CDC6 suppressed the proliferation of Hela cells and PBMCs from SLE patients in vitro. We identified SLE-related genes and their alternative splicing events. The cell cycle pathway and the cell cycle-related biological processes are over-activated in SLE patients. We revealed a higher incidence of MXE events of CDC6, which may lead to its high expression in SLE patients. Upregulated cell cycle signaling and CDC6 may be related to the hyperproliferation and pathogenesis of SLE.

Immunoregulatory functions of mature CD10+ and immature CD10- neutrophils in sepsis patients

Introduction

Neutrophil plays a more and more important role in sepsis with paralysis of immunoregulation. Till now, there was no biomarker to identify and isolate the mature and immature neutrophils in sepsis patients. CD10 shows on mature neutrophils at the latest stages of its differentiation. Our study aimed to investigate whether CD10 was a valid biomarker for distinguishing immature and mature neutrophil subgroups under septic conditions and their immunoregulatory effects on lymphocytes.

Methods

Totally 80 healthy volunteers and 107 sepsis patients were recruited in this study. Fluorescence-conjugated anti-CD66b, and anti-CD10 monoclonal antibodies followed by incubation with specific anti-fluorochrome microbeads was used to isolate different subgroups of neutrophils. T cell apoptotic assays and T cell proliferation assays followed by flow cytometry analysis were used to evaluate the immunoregulatory effect of each subgroup of neutrophils.

Results

(1) The cytological morphology of CD10⁺ neutrophils was mature and that of CD10^- neutrophils was immature in sepsis patients. (2) Mature CD10⁺ neutrophils inhibited the proliferation of T cell and immature CD10^- neutrophils promoted the T cell proliferation.

Conclusion

(1) CD10 was a good biomarker to distinguish mature from immature neutrophils in sepsis patients. (2) Mature CD10⁺ and immature CD10^- neutrophils displayed opposite immunoregulatory effects on T cells in sepsis patients.

Dysregulated low-density granulocyte contributes to early spontaneous abortion

Spontaneous abortion (SA) is a common adverse pregnancy event with unclarified pathogenesis and limited therapeutic efficiency. Although most SA cases with the euploid embryo(s) are associated with immunological factors, the contribution of low-density granulocyte (LDG) in SA pathogenesis is rarely reported. This study aimed to investigate the serial characteristics and possible contribution of LDG and their subpopulations in early pregnancy, especially in early SA. Unpregnant (UP), normally pregnant (NP), and SA women were recruited, and the peripheral blood and endometrium/decidua were collected for LDG isolation and histological observation. The percentage, phenotype, and subpopulations of LDG were analyzed via flow cytometric analysis, and the ability of Nets formation was assessed by immunofluorescent and immunohistochemical assays. As a result, 43 participants were enrolled, including 10 UP, 15 NP, and 18 SA women. Compared with the UP group, the LDG percentage in peripheral blood mononuclear cells (PBMCs) and decidual immune cells (DICs) increased in the NP group, while the loss of this increase was observed in the SA group. Meanwhile, CD16^int/- cell percentage in peripheral blood LDG (PB-LDG) increased in the NP and SA groups, and insufficient activation of CD16^hi PB-LDG characterized by reduced CD11b expression was discovered in the SA group. Moreover, the LDG percentage in DICs was higher than that in PBMCs, and the decidual LDG (D-LDG) showed a surface marker expression profile that is easier to be activated in the pregnant cohort (NP + SA women). Finally, increased decidual Nets formation was observed in the SA group compared with the NP group, and more Nets formation was detected in D-LDG of NP and SA women following PMA stimulation. Overall, LDG participates in the maintenance of early pregnancy, while dysregulated LDG is responsible for early SA, providing novel potential targets for further exploration of SA pathogenesis and therapeutics.

Loss-of-function variants in SAT1 cause X-linked childhood-onset systemic lupus erythematosus

OBJECTIVES

Families that contain multiple siblings affected with childhood onset of systemic lupus erythematosus (SLE) likely have strong genetic predispositions. We performed whole exome sequencing (WES) to identify familial rare risk variants and to assess their effects in lupus.

METHODS

Sanger sequencing validated the two ultra-rare, predicted pathogenic risk variants discovered by WES and identified additional variants in 562 additional patients with SLE. Effects of a splice site variant and a frameshift variant were assessed using a Minigene assay and CRISPR/Cas9-mediated knock-in (KI) mice, respectively.

RESULTS

The two familial ultra-rare, predicted loss-of-function (LOF) SAT1 variants exhibited X-linked recessive Mendelian inheritance in two unrelated African-American families. Each LOF variant was transmitted from the heterozygous unaffected mother to her two sons with childhood-onset SLE. The p.Asp40Tyr variant affected a splice donor site causing deleterious transcripts. The young hemizygous male and homozygous female Sat1 p.Glu92Leufs*6 KI mice spontaneously developed splenomegaly, enlarged glomeruli with leucocyte infiltration, proteinuria and elevated expression of type I interferon-inducible genes. SAT1 is highly expressed in neutrophils and encodes spermidine/spermine-N1-acetyltransferase 1 (SSAT1), a rate-limiting enzyme in polyamine catabolism. Young male KI mice exhibited neutrophil defects and decreased proportions of Foxp3 +CD4+ T-cell subsets. Circulating neutrophil counts and proportions of Foxp3 +CD4+ T cells correlated with decreased plasma levels of spermine in treatment-naive, incipient SLE patients.

CONCLUSIONS

We identified two novel SAT1 LOF variants, showed the ability of the frameshift variant to confer murine lupus, highlighted the pathogenic role of dysregulated polyamine catabolism and identified SAT1 LOF variants as new monogenic causes for SLE.

Clinical improvement of sepsis by extracorporeal centrifugal leukocyte apheresis in a porcine model

BACKGROUND

Extracorporeal blood purification therapies targeting removal of the downstream products of the inflammatory cascade in sepsis have failed to improve mortality. As an upstream process of the inflammatory cascade, activated white blood cells should be a potential therapeutic target for sepsis, and the effect of removing such cells by extracorporeal centrifugal leukocytapheresis (LCAP) is worth considering.

METHODS

Fourteen peritonitis-induced septic pigs were randomly assigned to receive a sham operation (control group, n = 7) or one session of LCAP at 12 h after sepsis induction (treatment group, n = 7). Samples from peripheral blood at various time-points and from LCAP collection were tested. All pigs were euthanized at 48 h, and lung, kidney, liver and spleen tissues were obtained for histopathological examination.

RESULTS

Two pigs died in accidents before the induction of sepsis, and 12 pigs were finally included for the statistical analysis. A significant clinical improvement was present in the treatment group relative to the control group in terms of the mean arterial blood pressure (MAP), oxygen tension (PaO2), lactic acid level, oxygenation index (PaO2/FiO2), and carbon dioxide tension (PaCO2, P < 0.05). Flow cytometry tests showed that a mixture of B cells, dendritic cells, T helper cells, cytotoxic T cells, monocytes and neutrophils were removed from the circulation by LCAP, resulting in sepsis-induced change trends in the control cells; these change trends were all flattened in the treatment group, although nonsignificantly.

CONCLUSIONS

LCAP may exert a wide-spectrum and bidirectional immunomodulatory effect on sepsis, accompanied by improvements in hemodynamics and oxygenation status.

Single-cell transcriptome profiling reveals heterogeneous neutrophils with prognostic values in sepsis

Neutrophils constitute the largest proportion of nucleated peripheral blood cells, and neutrophils have substantial heterogeneity. We profiled nearly 300,000 human peripheral blood cells in this study using single-cell RNA sequencing. A large proportion (>50%) of these cells were annotated as neutrophils. Neutrophils were further clustered into four subtypes, including Neu1, Neu2, Neu3, and Neu4. Neu1 is characterized by high expression of MMP9, HP, and RGL4. Neu1 was associated with septic shock and significantly correlated with the sequential organ failure assessment (SOFA) score. A gene expression module in Neu1 named Neu1_C (characterized by expression of NFKBIA, CXCL8, G0S2, and FTH1) was highly predictive of septic shock with an area under the curve of 0.81. The results were extensively validated in external bulk datasets by using single-cell deconvolution methods. In summary, our study establishes a general framework for studying neutrophil-related mechanisms, prognostic biomarkers, and potential therapeutic targets for septic shock.

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Neutrophils were clustered into four subtypes, including Neu1, Neu2, Neu3, and Neu4

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Neu1 was associated with septic shock

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Neu1 was correlated with the sequential organ failure assessment (SOFA) score

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A gene expression module in Neu1 named Neu1_C was highly predictive of septic shock

Insights into the role of neutrophils in neuropsychiatric systemic lupus erythematosus: Current understanding and future directions

Central nervous system (CNS) involvement of systemic lupus erythematosus (SLE), termed neuropsychiatric SLE (NPSLE), is a major and debilitating manifestation of the disease. While patients with SLE mostly complain of common neuropsychological symptoms such headache and mild mood disorders that may not even be technically attributed to SLE, many SLE patients present with life-threatening NPSLE syndromes such as cerebrovascular disease, seizures and psychosis that are equally challenging in terms of early diagnosis and therapy. While we are just beginning to unravel some mysteries behind the immunologic basis of NPSLE, advancements in the mechanistic understanding of the complex pathogenic processes of NPSLE have been emerging through recent murine and human studies. The pathogenic pathways implicated in NPSLE are multifarious and various immune effectors such as cell-mediated inflammation, autoantibodies and cytokines including type I interferons have been found to act in concert with the disruption of the blood-brain barrier (BBB) and other neurovascular interfaces. Beyond antimicrobial functions, neutrophils are emerging as decision-shapers during innate and adaptive immune responses. Activated neutrophils have been recognized to be involved in ischemic and infective processes in the CNS by releasing neutrophil extracellular traps (NETs), matrix metalloproteinase-9 and proinflammatory cytokines. In the context of NPSLE, these mechanisms contribute to BBB disruption, neuroinflammation and externalization of modified proteins on NETs that serve as autoantigens. Neutrophils that sediment within the peripheral blood mononuclear cell fraction after density centrifugation of blood are generally defined as low-density neutrophils (LDNs) or low-density granulocytes. LDNs are a proinflammatory subset of neutrophils that are increased with SLE disease activity and are primed to undergo NETosis and release cytokines such as interferon-α and tumor necrosis factor. This review discusses the immunopathogenesis of NPSLE with a focus on neutrophils as a core mediator of the disease and potential target for translational research in NPSLE.

Predicted Immune-Related Genes and Subtypes in Systemic Lupus Erythematosus Based on Immune Infiltration Analysis

Objective

The present investigation is aimed at identifying key immune-related genes linked with SLE and their roles using integrative analysis of publically available gene expression datasets.

Methods

Four gene expression datasets pertaining to SLE, 2 from whole blood and 2 experimental PMBC, were sourced from GEO. Shared differentially expressed genes (DEG) were determined as SLE-related genes. Immune cell infiltration analysis was performed using CIBERSORT, and case samples were subjected to k-means cluster analysis using high-abundance immune cells. Key immune-related SLE genes were identified using correlation analysis with high-abundance immune cells and subjected to functional enrichment analysis for enriched Gene Ontology Biological Processes and KEGG pathways. A PPI network of genes interacting with the key immune-related SLE genes was constructed. LASSO regression analysis was performed to identify the most significant key immune-related SLE genes, and correlation with clinicopathological features was examined.

Results

309 SLE-related genes were identified and found functionally enriched in several pathways related to regulation of viral defenses and T cell functions. k-means cluster analysis identified 2 sample clusters which significantly differed in monocytes, dendritic cell resting, and neutrophil abundance. 65 immune-related SLE genes were identified, functionally enriched in immune response-related signaling, antigen receptor-mediated signaling, and T cell receptor signaling, along with Th17, Th1, and Th2 cell differentiation, IL-17, NF-kappa B, and VEGF signaling pathways. LASSO regression identified 9 key immune-related genes: DUSP7, DYSF, KCNA3, P2RY10, S100A12, SLC38A1, TLR2, TSR2, and TXN. Imputed neutrophil percentage was consistent with their expression pattern, whereas anti-Ro showed the inverse pattern as gene expression.

Conclusions

Comprehensive bioinformatics analyses revealed 9 key immune-related genes and their associated functions highly pertinent to SLE pathogenesis, subtypes, and identified valuable candidates for experimental research.

Screening Biomarkers for Systemic Lupus Erythematosus Based on Machine Learning and Exploring Their Expression Correlations With the Ratios of Various Immune Cells

Background

Systemic lupus erythematosus (SLE) is an autoimmune illness caused by a malfunctioning immunomodulatory system. China has the second highest prevalence of SLE in the world, from 0.03% to 0.07%. SLE is diagnosed using a combination of immunological markers, clinical symptoms, and even invasive biopsy. As a result, genetic diagnostic biomarkers for SLE diagnosis are desperately needed.

Method

From the Gene Expression Omnibus (GEO) database, we downloaded three array data sets of SLE patients' and healthy people's peripheral blood mononuclear cells (PBMC) (GSE65391, GSE121239 and GSE61635) as the discovery metadata (n_SLE = 1315, n_normal = 122), and pooled four data sets (GSE4588, GSE50772, GSE99967, and GSE24706) as the validate data set (n_SLE = 146, n_normal = 76). We screened the differentially expressed genes (DEGs) between the SLE and control samples, and employed the least absolute shrinkage and selection operator (LASSO) regression, and support vector machine recursive feature elimination (SVM-RFE) analyze to discover possible diagnostic biomarkers. The candidate markers' diagnostic efficacy was assessed using the receiver operating characteristic (ROC) curve. The reverse transcription quantitative polymerase chain reaction (RT-qPCR) was utilized to confirm the expression of the putative biomarkers using our own Chinese cohort (n_SLE = 13, n_normal = 10). Finally, the proportion of 22 immune cells in SLE patients was determined using the CIBERSORT algorithm, and the correlations between the biomarkers' expression and immune cell ratios were also investigated.

Results

We obtained a total of 284 DEGs and uncovered that they were largely involved in several immune relevant pathways, such as type І interferon signaling pathway, defense response to virus, and inflammatory response. Following that, six candidate diagnostic biomarkers for SLE were selected, namely ABCB1, EIF2AK2, HERC6, ID3, IFI27, and PLSCR1, whose expression levels were validated by the discovery and validation cohort data sets. As a signature, the area under curve (AUC) values of these six genes reached to 0.96 and 0.913, respectively, in the discovery and validation data sets. After that, we checked to see if the expression of ABCB1, IFI27, and PLSCR1 in our own Chinese cohort matched that of the discovery and validation sets. Subsequently, we revealed the potentially disturbed immune cell types in SLE patients using the CIBERSORT analysis, and uncovered the most relevant immune cells with the expression of ABCB1, IFI27, and PLSCR1.

Conclusion

Our study identified ABCB1, IFI27, and PLSCR1 as potential diagnostic genes for Chinese SLE patients, and uncovered their most relevant immune cells. The findings in this paper provide possible biomarkers for diagnosing Chinese SLE patients.

Proteomic Analyses Reveal Higher Levels of Neutrophil Activation in Men Than in Women With Systemic Lupus Erythematosus

Objective

Systemic Lupus Erythematosus (SLE) is a systemic autoimmune disease that displays a significant gender difference in terms of incidence and severity. However, the underlying mechanisms accounting for sexual dimorphism remain unclear. The aim of this work was to reveal the heterogeneity in the pathogenesis of SLE between male and female patients.

Methods

PBMC were collected from 15 patients with SLE (7 males, 8 females) and 15 age-matched healthy controls (7 males, 8 females) for proteomic analysis. The proteins of interest were validated in independent samples (6 male SLE, 6 female SLE). Biomarkers for neutrophil activation (calprotectin), neutrophil extracellular traps (cell-free DNA and elastase), and reactive oxygen species (glutathione) were measured, using enzyme-linked immunosorbent assay, in plasma obtained from 52 individuals.

Results

Enrichment analysis of proteomic data revealed that type I interferon signaling and neutrophil activation networks mapped to both male and female SLE, while male SLE has a higher level of neutrophil activation compared with female SLE. Western blot validated that PGAM1, BST2, and SERPINB10 involved in neutrophil activation are more abundant in male SLE than in female SLE. Moreover, biomarkers of neutrophil activation and reactive oxygen species were increased in male SLE compared with female SLE.

Conclusion

Type I interferon activation is a common signature in both male and female SLE, while neutrophil activation is more prominent in male SLE compared with female SLE. Our findings define gender heterogeneity in the pathogenesis of SLE and may facilitate the development of gender-specific treatments.

Neutrophil subsets and their differential roles in viral respiratory diseases

Neutrophils play significant roles in immune homeostasis and as neutralizers of microbial infections. Recent evidence further suggests heterogeneity of neutrophil developmental and activation states that exert specialized effector functions during inflammatory disease conditions. Neutrophils can play multiple roles during viral infections, secreting inflammatory mediators and cytokines that contribute significantly to host defense and pathogenicity. However, their roles in viral immunity are not well understood. In this review, we present an overview of neutrophil heterogeneity and its impact on the course and severity of viral respiratory infectious diseases. We focus on the evidence demonstrating the crucial roles neutrophils play in the immune response toward respiratory infections, using influenza as a model. We further extend the understanding of neutrophil function with the studies pertaining to COVID-19 disease and its neutrophil-associated pathologies. Finally, we discuss the relevance of these results for future therapeutic options through targeting and regulating neutrophil-specific responses.

Differential Functional Responses of Neutrophil Subsets in Severe COVID-19 Patients

Neutrophils play a significant role in determining disease severity following SARS-CoV-2 infection. Gene and protein expression defines several neutrophil clusters in COVID-19, including the emergence of low density neutrophils (LDN) that are associated with severe disease. The functional capabilities of these neutrophil clusters and correlation with gene and protein expression are unknown. To define host defense and immunosuppressive functions of normal density neutrophils (NDN) and LDN from COVID-19 patients, we recruited 64 patients with severe COVID-19 and 26 healthy donors (HD). Phagocytosis, respiratory burst activity, degranulation, neutrophil extracellular trap (NET) formation, and T-cell suppression in those neutrophil subsets were measured. NDN from severe/critical COVID-19 patients showed evidence of priming with enhanced phagocytosis, respiratory burst activity, and degranulation of secretory vesicles and gelatinase and specific granules, while NET formation was similar to HD NDN. COVID LDN response was impaired except for enhanced NET formation. A subset of COVID LDN with intermediate CD16 expression (CD16^Int LDN) promoted T cell proliferation to a level similar to HD NDN, while COVID NDN and the CD16^Hi LDN failed to stimulate T-cell activation. All 3 COVID-19 neutrophil populations suppressed stimulation of IFN-γ production, compared to HD NDN. We conclude that NDN and LDN from COVID-19 patients possess complementary functional capabilities that may act cooperatively to determine disease severity. We predict that global neutrophil responses that induce COVID-19 ARDS will vary depending on the proportion of neutrophil subsets.

Neutrophil to lymphocyte ratio and platelet to lymphocyte ratio reflect disease activity and flares in patients with systemic lupus erythematosus - A prospective study

OBJECTIVES

To determine the association between neutrophil to lymphocyte ratio (NLR) and platelet to lymphocyte ratio (PLR) with disease activity and flares in an inception cohort of patients with systemic lupus erythematosus (SLE) using a prospective study design.

METHODS

Consecutive adult patients (age≥21) who fulfilled the 1997 American College of Rheumatology (ACR) or the 2012 Systemic Lupus International Collaboration Clinic Classification (SLICC) Criteria for SLE were followed every 3 months, with SLE disease activity assessed by using SLEDAI-2K, and disease flares defined and captured by the SELENA-SLEDAI Flare Index (SFI). NLR and PLR were computed from the automated machine-counted blood count differentials. Linear mixed model and generalized estimating equation model were constructed to analyze the associations between NLR/PLR and SLEDAI-2K and disease flares, with multivariate adjustments.

RESULTS

Of 290 patients recruited, the median (IQR) duration of follow-up and baseline SLEDAI-2K were 4.7 (3.2-6.1) years and 2 (0.5-3.5), respectively. On multivariable analyses, NLR was shown to be positively and significantly associated with SLEDAI-2K (estimate of coefficient (β)=0.05, P<0.01) and severe disease flares (odds ratio [OR] 1.05, P<0.05), but not with overall disease flares [OR 1.02, non-significant]. While PLR was shown to be positively associated with SLEDAI-2K [β=0.09, P<0.05], no statistically significant association between PLR and overall or severe disease flares was found [OR 1.00 and OR 1.06 respectively, non-significant].

CONCLUSION

Derived readily from automated blood count differentials, the NLR potentially serves as a surrogate prospective marker of disease activity and severe disease flares in SLE patients.

Association between serum low-density neutrophils and acute-onset and recurrent Guillain-Barré syndrome

BACKGROUND AND AIM

Guillain-Barré syndrome (GBS) is one of the most common causes of acute flaccid paralysis. A timely assessment of this disease condition and its treatments are of vital importance to patients diagnosed with GBS. The purpose of this study is to investigate the variation trend of neutrophils along with disease courses and assess the prognostic value of serum low-density neutrophils (LDNs) in the acute-onset and recurrence of GBS.

METHODS

A total of 176 GBS patients were recruited. Patients were evaluated with Medical Research Council (MRC) sum score and the Hughes Functional Grading Scale score upon admission. Peripheral blood samples were collected for routine testing. Flow cytometry analysis was performed to identify LDNs. All patients were followed up to collect disease condition data.

RESULTS

The total neutrophil ratios and counts were significantly higher in patients with acute-onset GBS compared to healthy controls (HCs). These counts/ratios decreased during remission and re-elevated in recurrent GBS patients. However, no correlation was observed between the total neutrophil counts/ratios and the MRC sum score. The LDNs collected from different GBS courses were identified using flow cytometry. The counts and ratios were significantly higher in acute-onset GBS and recurrent GBS compared to HCs and patients in remission. The LDN counts/ratios displayed a negative correlation with the MRC sum scores in acute-onset GBS and recurrent GBS.

CONCLUSION

Our findings suggest that LDN counts/ratios are positively correlated with the acute-onset and recurrence of GBS and its severity. Therefore, LDNs might serve as an accessible prognostic indicator for disease progression monitoring.

A meta-analysis of clinical manifestations in asian systemic lupus erythematous: The effects of ancestry, ethnicity and gender

OBJECTIVES

Systemic lupus erythematosus (SLE) in Asians is a unique patient group that has been thought to present with more severe organ involvement in comparison to their non-Asian counterparts. We set out to perform a meta-analysis to compare clinical manifestations between ancestries, with a focus on Southeast Asian ethnicities and gender.

MATERIALS AND METHODS

A cross-sectional study was performed in conjunction with a meta-analysis to identify differences in prevalences of SLE clinical manifestations. Searches were conducted on Medline for articles comparing between: (i) Asian and non-Asian ancestry; (ii) Southeast Asian ethnicities (Chinese, Malay and Indian); and (iii) male and female Asians. Using random effects model, effect sizes as odd ratios were pooled with DerSimonian and Laird's model.

RESULTS

A total of 13 articles were identified and pooled together with our study for this meta-analysis. Comparing among patients of Asian with Non-Asian/European ancestries, no significance difference was found in severe organ manifestations such as renal and neurological involvement [odds ratio (OR): 1.398, p= 0.320 and OR: 1.224, p= 0.526 respectively]. There was significantly greater proportion of Asian SLE patients with thrombocytopenia compared to non-Asian SLE. Chinese SLE patients were less likely to have oral ulcers compared to Indian SLE patients. Lastly, Asian male SLE patients had greater incidence of renal involvement and thrombocytopenia compared to Asian female SLE patients.

CONCLUSIONS

Severe SLE manifestations such as renal and neurological involvement were not significantly more frequent in Asian SLE compared to non-Asian/European SLE in this analysis.

Immunosuppression Affects Neutrophil Functions: Does Calcineurin-NFAT Signaling Matter?

Neutrophils are innate immune cells with important roles in antimicrobial defense. However, impaired or dysregulated neutrophil function can result in host tissue damage, loss of homeostasis, hyperinflammation or pathological immunosuppression. A central link between neutrophil activation and immune outcomes is emerging to be the calcineurin-nuclear factor of activated T cells (NFAT) signaling pathway, which is activated by neutrophil detection of a microbial threat via pattern recognition receptors and results in inflammatory cytokine production. This potent pro-inflammatory pathway is also the target of several immunosuppressive drugs used for the treatment of autoimmune disorders, during solid organ and hematopoietic cell transplantations, and as a part of anti-cancer therapy: but what effects these drugs have on neutrophil function, and their broader consequences for immune homeostasis and microbial defense are not yet known. Here, we bring together the emerging literature describing pathology- and drug- induced neutrophil impairment, with particular focus on their effects on calcineurin-NFAT signaling in the innate immune compartment.

Tumor-Derived Factors Differentially Affect the Recruitment and Plasticity of Neutrophils

Neutrophils play a key role in cancer biology. In contrast to circulating normal-density neutrophils (NDN), the amount of low-density neutrophils (LDN) significantly increases with tumor progression. The correlation between these neutrophil subpopulations and intratumoral neutrophils (TANs) is still under debate. Using 4T1 (breast) and AB12 (mesothelioma) tumor models, we aimed to elucidate the source of TANs and to assess the mechanisms driving neutrophils' plasticity in cancer. Both NDN and LDN were found to migrate in response to CXCL1 and CXCL2 exposure, and co-infiltrate the tumor site ex vivo and in vivo, although LDN migration into the tumor was higher than NDN. Tumor-derived factors and chemokines, particularly CXCL1, were found to drive neutrophil phenotypical plasticity, inducing NDN to transition towards a low-density state (LD-NDN). LD-NDN appeared to differ from NDN by displaying a phenotypical profile similar to LDN in terms of nuclear morphology, surface receptor markers, decreased phagocytic abilities, and increased ROS production. Interestingly, all three subpopulations displayed comparable cytotoxic abilities towards tumor cells. Our data suggest that TANs originate from both LDN and NDN, and that a portion of LDN derives from NDN undergoing phenotypical changes. NDN plasticity resulted in a change in surface marker expression and functional activity, gaining characteristics of LDN.

Neutrophil extracellular traps and neutrophil-derived mediators as possible biomarkers in bronchial asthma

Neutrophils (PMNs) contain and release a powerful arsenal of mediators, including several granular enzymes, reactive oxygen species (ROS) and neutrophil extracellular traps (NETs). Although airway neutrophilia is associated with severity, poor response to glucocorticoids and exacerbations, the pathophysiological role of neutrophils in asthma remains poorly understood. Twenty-four patients with asthma and 22 healthy controls (HCs) were prospectively recruited. Highly purified peripheral blood neutrophils (> 99%) were evaluated for ROS production and activation status upon stimulation with lipopolysaccharide (LPS), N-formylmethionyl-leucyl-phenylalanine (fMLP) and phorbol 12-myristate 13-acetate (PMA). Plasma levels of myeloperoxidase (MPO), CXCL8, matrix metalloproteinase-9 (MMP-9), granulocyte–monocyte colony-stimulating factor (GM-CSF) and vascular endothelial growth factor (VEGF-A) were measured by ELISA. Plasma concentrations of citrullinated histone H3 (CitH3) and circulating free DNA (dsDNA) were evaluated as NET biomarkers. Activated PMNs from asthmatics displayed reduced ROS production and activation status compared to HCs. Plasma levels of MPO, MMP-9 and CXCL8 were increased in asthmatics compared to HCs. CitH3 and dsDNA plasma levels were increased in asthmatics compared to controls and the CitH3 concentrations were inversely correlated to the % decrease in FEV₁/FVC in asthmatics. These findings indicate that neutrophils and their mediators could have an active role in asthma pathophysiology.

Low-Density Neutrophils in Healthy Individuals Display a Mature Primed Phenotype

Neutrophils are the most abundant leukocytes in human peripheral blood, comprising about 70% of all leukocytes. They are regarded as the first line of defense of the innate immune system, but neutrophils have also the ability of regulating the adaptive immune response. Recently, However, multiple phenotypes and functional states of neutrophils have been reported, particularly in inflammation, autoimmunity, and cancer. One possible subtype of neutrophils, the so-called low-density neutrophils (LDN) is found among mononuclear cells (MNC), monocytes and lymphocytes, after separating the leukocytes from blood by density gradient centrifugation. LDN increase in numbers during several pathological conditions. However, LDN present in healthy conditions have not been investigated further. Therefore, in order to confirm the presence of LDN in blood of healthy individuals and to explore some of their cellular functions, neutrophils and MNC were isolated by density gradient centrifugation. Purified neutrophils were further characterized by multicolor flow cytometry (FACS) and then, using the same FACS parameters cells in the MNC fraction were analyzed. Within the MNC, LDN were consistently found. These LDN had a normal mature neutrophil morphology and displayed a CD10+, CD11b+, CD14low, CD15high, CD16bhigh, CD62L+, CD66b+, and CXCR4+ phenotype. These LDN had an enhanced reactive oxygen species (ROS) production and increased phagocytic capacity and were able to produce neutrophil extracellular traps (NET) similarly to neutrophils. These data confirm the presence of a small number of LDN is blood of healthy individuals and suggest that these LDN represent mature cells with a primed phenotype.

Neutrophil-to-Lymphocyte Ratio Predicts Development of Immune-Related Adverse Events and Outcomes from Immune Checkpoint Blockade: A Case-Control Study

The utility of neutrophil-to-lymphocyte ratio (NLR) and platelet-to-lymphocyte ratio (PLR) utility in predicting immune-related adverse events (irAEs) and survival have not been well studied in the context of treatment with immune checkpoint inhibitors (ICIs). We performed a case-control study of cancer patients who received at least one dose of ICI in a tertiary hospital. We examined NLR and PLR in irAE cases and controls. Logistic and Cox regression models were used to identify independent risk factors for irAEs, progression-free survival (PFS), and overall survival (OS). The study included 91 patients with irAEs and 56 controls. Multiple logistic regression showed that NLR < 3 at baseline was associated with higher occurrence of irAEs. Multivariate Cox regression showed that development of irAEs and reduction in NLR from baseline to week 6 were associated with longer PFS. Higher NLR values at baseline and/or week 6 were independently associated with shorter OS. A reduction in NLR from baseline to week 6 was associated with longer OS. In this study of cancer patients treated with ICIs, NLR has a bidirectional relationship with adverse outcomes. Lower NLR was associated with increased occurrence of irAEs while higher NLR values were associated with worse clinical outcomes.

Studying Neutrophil Function in vitro: Cell Models and Environmental Factors

Neutrophils are the most abundant immune cell type in the blood and constitute the first line of defense against invading pathogens. Despite their important role in many diseases, they are challenging to study due to their short life span and the inability to cryopreserve or expand them in vitro. Thus, research into neutrophils has to rely on cells freshly isolated from peripheral blood of human donors, introducing donor-dependent variation in the experimental data. To counteract these problems, researchers tried to develop adequate cell models, such as cell lines. For those functional studies that cannot rely on cell models, a standardization of protocols regarding neutrophil purification and culturing could be a solution. In this review, we provide an overview of the most commonly used models for neutrophil function (HL-60, PLB-985, NB4, Kasumi-1 and induced pluripotent stem cells). In addition, we describe the effects of glucose concentration, pH, oxygen tension and temperature on neutrophil function.