Neutrophils: Need for Standardized Nomenclature

The role of neutrophils in allergic disease

Neutrophils are short-lived cells of the innate immune system and represent 50-70% of the circulating leucocytes. Their primary role is antimicrobial defence which they accomplish through rapid migration to sites of inflammation followed by phagocytosis, degranulation, and the release of neutrophil extracellular traps (NETosis). While previously considered terminally differentiated cells, they have been shown to have great adaptability and to play a role in conditions ranging from cancer to autoimmunity. This review focuses on their role in allergic disease. In particular: their role as potential amplifiers of type 1 hypersensitivity reactions leading to anaphylaxis; their involvement in alternative pathways of food and drug allergy; their role in allergic rhinitis and asthma and neutrophil dysfunction in atopic dermatitis. The use of potential biomarkers and therapeutic targets is also discussed with a view to guiding future research.

Effect of neutrophils on tumor immunity and immunotherapy resistance with underlying mechanisms

Neutrophils are key mediators of the immune response and play essential roles in the development of tumors and immune evasion. Emerging studies indicate that neutrophils also play a critical role in the immunotherapy resistance in cancer. In this review, firstly, we summarize the novel classification and phenotypes of neutrophils and describe the regulatory relationships between neutrophils and tumor metabolism, flora microecology, neuroendocrine and tumor therapy from a new perspective. Secondly, we review the mechanisms by which neutrophils affect drug resistance in tumor immunotherapy from the aspects of the immune microenvironment, tumor antigens, and epigenetics. Finally, we propose several promising strategies for overcoming tumor immunotherapy resistance by targeting neutrophils and provide new research ideas in this area.

CXCR1+ neutrophil infiltration orchestrates response to third-generation EGFR-TKI in EGFR mutant non-small-cell lung cancer

Although third-generation Epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKI) is standard of care for patients with EGFR-mutant Non-small cell lung cancer (NSCLC), little is known about the predictors of response or resistance. Here, we integrated single-cell RNA (scRNA) sequencing, bulk RNA sequencing, multiplexed immunofluorescence and flow cytometry data from pretreatment and post-resistant tumor samples of EGFR-mutant NSCLC patients received third-generation EGFR-TKIs. We show that resistant samples had a markedly enriched CXCR1+ neutrophils infiltration (P < 0.01) than pretreatment samples, which were distinguished from other subtypes of neutrophils and displayed immunosupressive characteristics. Spatial analysis showed that increased CXCR1+ neutrophils predominantly infiltrated into the tumor core in resistant samples and the average distance of neutrophils to tumor cells markedly reduced from 33 to 19 μm. Deep analysis of scRNA and bulk RNA sequencing data revealed the increased interactions between CXCR1+ neutrophils and tumor cells and activated TNF-α/NF-κB signaling pathway in tumor cells of resistant samples. In vitro and in vivo experiments validated that CXCR1+ neutrophils resulted in resistance to third-generation EGFR-TKI via activating TNF-α/NF-κB signaling pathway in tumor cells. Importantly, patients with low pretreatment CXCR1+ neutrophil infiltration abundance had a dramatically longer progression-free survival (11.8 vs. 7.5 months; P = 0.019) and overall survival (33.0 vs. 23.5 months; P = 0.029) than those with high infiltration abundance. Collectively, these findings suggest that CXCR1+ neutrophils infiltration was associated with the efficacy of third-generation EGFR-TKI in patients with EGFR-mutant NSCLC.

Low-Density Neutrophil Levels Are Correlated with Sporotrichosis Severity: Insights into Subcutaneous Fungal Infection

Low-density neutrophils (LDNs) constitute a distinct subset of neutrophils among peripheral blood mononuclear cells. They are key mediators in systemic infections, amplifying inflammatory responses and potentially influencing disease severity and chronicity. However, their roles in subcutaneous fungal infections have not been previously investigated. In this study, we observed increased neutrophil counts in the blood and tissues of sporotrichosis patients through automated blood analysis, histology, and immunohistochemistry. Additionally, we found elevated granulocyte colony-stimulating factor (G-CSF) levels by enzyme-linked immunosorbent assays. Flow cytometry analysis revealed a significant increase in CD16+CD66b+ LDNs compared with healthy controls. In vitro stimulation with Sporothrix globosa induced LDN generation. We observed positive correlations of LDN frequency with levels of C-reactive protein and myeloperoxidase. Conversely, G-CSF levels were negatively correlated with LDN frequency. LDNs exhibited a combined mature/immature phenotype. Notably, transcriptomic analysis showed downregulation of anti-inflammatory signaling pathways in LDNs; functional assays also demonstrated reduced phagocytosis, reactive oxygen species production, and neutrophil extracellular trap formation after stimulation with Sporothrix globosa. Degranulation did not exhibit significant changes, suggesting that LDNs constitute an impaired subpopulation. Our findings in the context of subcutaneous fungal infections indicate that LDN levels are significantly elevated in sporotrichosis and positively correlated with disease severity.

CTC-neutrophil interaction: A key driver and therapeutic target of cancer metastasis

Circulating tumor cells (CTCs) are cancer cells that detach from the primary tumor and enter the bloodstream, where they can seed new metastatic lesions in distant organs. CTCs are often associated with white blood cells (WBCs), especially neutrophils, the most abundant and versatile immune cells in the blood. Neutrophils can interact with CTCs through various mechanisms, such as cell-cell adhesion, cytokine secretion, protease release, and neutrophil extracellular traps (NETs) formation. These interactions can promote the survival, proliferation, invasion, and extravasation of CTCs, as well as modulate the pre-metastatic niche and the tumor microenvironment. Therefore, inhibiting CTC-neutrophils interaction could be a potential strategy to reduce tumor metastasis and improve the prognosis of cancer patients. In this review, we summarize the current literature on CTC-neutrophils interaction' role in tumor metastasis and discuss the possible therapeutic approaches to target this interaction.

Improving efficacy of TNBC immunotherapy: based on analysis and subtyping of immune microenvironment

Triple-negative breast cancer (TNBC) is a highly aggressive type of breast cancer that encompasses several distinct subtypes. Recent advances in immunotherapy offer a promising future for the treatment of these highly heterogeneous and readily metastatic tumors. Despite advancements, the efficacy of immunotherapy remains limited as shown by unimproved efficacy of PD-L1 biomarker and limited patient benefit. To enhance the effectiveness of TNBC immunotherapy, we conducted investigation on the microenvironment, and corresponding therapeutic interventions of TNBC and recommended further investigation into the identification of additional biomarkers that can facilitate the subtyping of TNBC for more targeted therapeutic approaches. TNBC is a highly aggressive subtype with dismal long-term survival due to the lack of opportunities for traditional endocrine and targeted therapies. Recent advances in immunotherapy have shown promise, but response rates can be limited due to the heterogeneous tumor microenvironments and developed therapy resistance, especially in metastatic cases. In this review, we will investigate the tumor microenvironment of TNBC and corresponding therapeutic interventions. We will summarize current subtyping strategies and available biomarkers for TNBC immunotherapy, with a particular emphasis on the need for further research to identify additional prognostic markers and refine tailored therapies for specific TNBC subtypes. These efforts aim to improve treatment sensitivity and ultimately enhance survival outcomes for advanced-stage TNBC patients.

The cGAS-STING Pathway Is Essential in Acute Ischemia-Induced Neutropoiesis and Neutrophil Priming in the Bone Marrow

Acute myocardial ischemia triggers a rapid mobilization of neutrophils from the bone marrow to peripheral blood, facilitating their infiltration into the infarcted myocardium. These cells are critical for inducing inflammation and contributing to myocardial repair. While neutrophils in infarcted tissue are better characterized, our understanding of whether and how ischemia regulates neutrophil production, differentiation, and functionality in the bone marrow remains limited. This study investigates these processes and the influence of the cGAS-STING pathway in the context of myocardial infarction. The cGAS-STING pathway detects aberrant DNA within cells, activates STING, and initiates downstream signaling cascades involving NFKB and IRF3. We analyzed neutrophils from bone marrow, peripheral blood, and infarct tissues using MI models generated from wild-type, Cgas -/- , and Sting -/- mice. These models are essential for studying neutropoiesis (neutrophil production and differentiation), as it involves multiple cell types. RNA sequencing analysis revealed that ischemia not only increased neutrophil production but also promoted cytokine signaling, phagocytosis, chemotaxis, and degranulation in the bone marrow before their release into the peripheral blood. Inhibition of the cGAS-STING pathway decreased neutrophil production after MI and down-regulated the same pathways activated by ischemia. Neutrophils lacking cGAS or STING were less mature, exhibited reduced activation, and decreased degranulation. Deletion of cGAS and STING decreased the expression of a large group of IFN-stimulated genes and IFIT1+ neutrophils from peripheral blood and the infarct tissue, suggesting that cGAS-STING plays an essential role in neutrophils with the IFN-stimulated gene signature. Importantly, transcriptomic analysis of Cgas -/- and Sting -/- neutrophils from bone marrow and MI tissues showed downregulation of similar pathways, indicating that the functionality developed in the bone marrow was maintained despite infarct-induced stimulation. These findings highlight the importance of neutropoiesis in dictating neutrophil function in target tissues, underscoring the critical role of the cGAS-STING pathway in neutrophil-mediated myocardial repair post-ischemia.

Emergence of dysfunctional neutrophils with a defect in arginase-1 release in severe COVID-19

Neutrophilia occurs in patients infected with SARS-CoV-2 (COVID-19) and is predictive of poor outcomes. Here, we link heterogenous neutrophil populations to disease severity in COVID-19. We identified neutrophils with features of cellular aging and immunosuppressive capacity in mild COVID-19 and features of neutrophil immaturity and activation in severe disease. The low-density neutrophil (LDN) number in circulating blood correlated with COVID-19 severity. Many of the divergent neutrophil phenotypes in COVID-19 were overrepresented in the LDN fraction and were less detectable in normal-density neutrophils. Functionally, neutrophils from patients with severe COVID-19 displayed defects in neutrophil extracellular trap formation and reactive oxygen species production. Soluble factors secreted by neutrophils from these patients inhibited T cell proliferation. Neutrophils from patients with severe COVID-19 had increased expression of arginase-1 protein, a feature that was retained in convalescent patients. Despite this increase in intracellular expression, there was a reduction in arginase-1 release by neutrophils into serum and culture supernatants. Furthermore, neutrophil-mediated T cell suppression was independent of arginase-1. Our results indicate the presence of dysfunctional, activated, and immature neutrophils in severe COVID-19.

Ex vivo study on the human blood neutrophil circadian features and effects of alpha1-antitrypsin and lipopolysaccharide

AIMS

Neutrophils perform various functions in a circadian-dependent manner; therefore, we investigated here whether the effect of alpha1-antitrypsin (AAT), used as augmentation therapy, is dependent on the neutrophil circadian clock. AAT is a vital regulator of neutrophil functions, and its qualitative and/or quantitative defects have significant implications for the development of respiratory diseases.

METHODS

Whole blood from 12 healthy women age years, mean (SD) 29.92 (5.48) was collected twice daily, 8 h apart, and incubated for 30 min at 37 °C alone or with additions of 2 mg/ml AAT (Respreeza) and/or 5 μg/ml lipopolysaccharide (LPS) from Escherichia coli. Neutrophils were then isolated to examine gene expression, migration and phagocytosis.

RESULTS

The expression of CD14, CD16, CXCR2 and SELL (encoding CD62L) genes was significantly higher while CDKN1A lower in the afternoon than in the morning neutrophils from untreated blood. Neutrophils isolated in the afternoon had higher migratory and phagocytic activity. Morning neutrophils isolated from AAT-pretreated blood showed higher expression of CXCR2 and SELL than those from untreated morning blood. Pretreatment of blood with AAT enhanced migratory properties of morning but not afternoon neutrophils. Of all genes analysed, only CXCL8 expression was strongly upregulated in morning and afternoon neutrophils isolated from LPS-pretreated blood, whereas CXCR2 expression was downregulated in afternoon neutrophils. The addition of AAT did not reverse the effects of LPS.

SIGNIFICANCE

The circadian clock of myeloid cells may affect the effectiveness of various therapies, including AAT therapy used to treat patients with AAT deficiency, and needs further investigation.

Pathogenesis and interaction of neutrophils and extracellular vesicles in noncancer liver diseases

Liver disease ranks as the eleventh leading cause of mortality, leading to approximately 2 million deaths annually worldwide. Neutrophils are a type of immune cell that are abundant in peripheral blood and play a vital role in innate immunity by quickly reaching the site of liver injury. They exert their influence on liver diseases through autocrine, paracrine, and immunomodulatory mechanisms. Extracellular vesicles, phospholipid bilayer vesicles, transport a variety of substances, such as proteins, nucleic acids, lipids, and pathogenic factors, for intercellular communication. They regulate cell communication and perform their functions by delivering biological information. Current research has revealed the involvement of the interaction between neutrophils and extracellular vesicles in the pathogenesis of liver disease. Moreover, more research has focused on targeting neutrophils as a therapeutic strategy to attenuate disease progression. Therefore, this article summarizes the roles of neutrophils, extracellular vesicles, and their interactions in noncancerous liver diseases.

Follicular Immune Landscaping Reveals a Distinct Profile of FOXP3hiCD4hi T Cells in Treated Compared to Untreated HIV

Follicular helper CD4hi T cells (TFH) are a major cellular pool for the maintenance of the HIV reservoir. Therefore, the delineation of the follicular (F)/germinal center (GC) immune landscape will significantly advance our understanding of HIV pathogenesis. We have applied multiplex confocal imaging, in combination with the relevant computational tools, to investigate F/GC in situ immune dynamics in viremic (vir-HIV), antiretroviral-treated (cART HIV) People Living With HIV (PLWH) and compare them to reactive, non-infected controls. Lymph nodes (LNs) from viremic and cART PLWH could be further grouped based on their TFH cell densities in high-TFH and low-TFH subgroups. These subgroups were also characterized by different in situ distributions of PD1hi TFH cells. Furthermore, a significant accumulation of follicular FOXP3hiCD4hi T cells, which were characterized by a low scattering in situ distribution profile and strongly correlated with the cell density of CD8hi T cells, was found in the cART-HIV low-TFH group. An inverse correlation between plasma viral load and LN GrzBhiCD8hi T and CD16hiCD15lo cells was found. Our data reveal the complex GC immune landscaping in HIV infection and suggest that follicular FOXP3hiCD4hi T cells could be negative regulators of TFH cell prevalence in cART-HIV.

Single-cell atlas of peripheral blood by CyTOF revealed peripheral blood immune cells metabolic alterations and neutrophil changes in intracranial aneurysm rupture

Previous studies have found that the peripheral immune environment is closely related to the occurrence and development of intracranial aneurysms. However, it remains unclear how the metabolism of peripheral blood mononuclear cells (PBMCs) and the composition of polymorphonuclear leukocytes (PMNs) changes in the process of intracranial aneurysm rupture. This study utilized cytometry by time of flight technology to conduct single-cell profiling analysis of PBMCs and PMNs from 72 patients with IAs. By comparing the expression differences of key metabolic enzymes in PBMCs between patients with ruptured intracranial aneurysms (RIAs) and unruptured intracranial aneurysms, we found that most PBMCs subsets from RIA group showed upregulation of rate-limiting enzymes related to the glycolytic pathway. By comparing the composition of PMNs, it was found that the proinflammatory CD101+HLA DR+ subsets were increased in the RIA group, accompanied by a decrease in the anti-inflammatory polymorphonuclear myeloid-derived suppressor cells. In conclusion, this study showed the changes in the peripheral immune profile of RIAs, which is helpful for our understanding of the mechanisms underlying peripheral changes and provides a direction for future related research.

A subpopulation of human bone marrow erythroid cells displays a myeloid gene expression signature similar to that of classic monocytes

Erythroid cells, serving as progenitors and precursors to erythrocytes responsible for oxygen transport, were shown to exhibit an immunosuppressive and immunoregulatory phenotype. Previous investigations from our research group have revealed an antimicrobial gene expression profile within murine bone marrow erythroid cells which suggested a role for erythroid cells in innate immunity. In the present study, we focused on elucidating the characteristics of human bone marrow erythroid cells through comprehensive analyses, including NanoString gene expression profiling utilizing the Immune Response V2 panel, a BioPlex examination of chemokine and TGF-beta family proteins secretion, and analysis of publicly available single-cell RNA-seq data. Our findings demonstrate that an erythroid cell subpopulation manifests a myeloid-like gene expression signature comprised of antibacterial immunity and neutrophil chemotaxis genes which suggests an involvement of human erythroid cells in the innate immunity. Furthermore, we found that human erythroid cells secreted CCL22, CCL24, CXCL5, CXCL8, and MIF chemokines. The ability of human erythroid cells to express these chemokines might facilitate the restriction of immune cells in the bone marrow under normal conditions or contribute to the ability of erythroid cells to induce local immunosuppression by recruiting immune cells in their immediate vicinity in case of extramedullary hematopoiesis.

Maturing neutrophils of lower density associate with thrombocytopenia in Puumala orthohantavirus-caused hemorrhagic fever with renal syndrome

Puumala orthohantavirus-caused hemorrhagic fever with renal syndrome (PUUV-HFRS) is characterized by strong neutrophil activation. Neutrophils are the most abundant immune cell type in the circulation and are specially equipped to rapidly respond to infections. They are more heterogenous than previously appreciated, with specific neutrophil subsets recently implicated in inflammation and immunosuppression. Furthermore, neutrophils can be divided based on their density to either low-density granulocytes (LDGs) or "normal density" polymorphonuclear cell (PMN) fractions. In the current study we aimed to identify and characterize the different neutrophil subsets in the circulation of PUUV-HFRS patients. PMNs exhibited an activation of antiviral pathways, while circulating LDGs were increased in frequency following acute PUUV-HFRS. Furthermore, cell surface marker expression analysis revealed that PUUV-associated LDGs are primarily immature and most likely reflect an increased neutrophil production from the bone marrow. Interestingly, both the frequency of LDGs and the presence of a "left shift" in blood associated with the extent of thrombocytopenia, one of the hallmarks of severe HFRS, suggesting that maturing neutrophils could play a role in disease pathogenesis. These results imply that elevated circulating LDGs might be a general finding in acute viral infections. However, in contrast to the COVID-19 associated LDGs described previously, the secretome of PUUV LDGs did not show significant immunosuppressive ability, which suggests inherent biological differences in the LDG responses that can be dependent on the causative virus or differing infection kinetics.

A review concerning the breast cancer-related tumour microenvironment

Breast cancer (BC) is currently the most common malignant tumour in women and one of the leading causes of their death around the world. New and increasingly personalised diagnostic and therapeutic tools have been introduced over the last few decades, along with significant advances regarding the study and knowledge related to BC. The tumour microenvironment (TME) refers to the tumour cell-associated cellular and molecular environment which can influence conditions affecting tumour development and progression. The TME is composed of immune cells, stromal cells, extracellular matrix (ECM) and signalling molecules secreted by these different cell types. Ever deeper understanding of TME composition changes during tumour development and progression will enable new and more innovative therapeutic strategies to become developed for targeting tumours during specific stages of its evolution. This review summarises the role of BC-related TME components and their influence on tumour progression and the development of resistance to therapy. In addition, an account on the modifications in BC-related TME components associated with therapy is given, and the completed or ongoing clinical trials related to this topic are presented.

Effect of exercise-induced Neutrophil maturation on skeletal muscle repair in vitro

Neutrophils as first line defender initiate a cascade of healing process immediately after muscle injury. At muscle injury site, neutrophils remove damaged muscle fibers and recruit other immune cells and these functions show in mature neutrophils. In the previous study, physical exercise can mediate neutrophils' functional changes such as phagocytosis and chemotaxis, though there is no research on how exercise-induced neutrophils contribute the muscle regeneration. In this present study, we investigated the maturation of neutrophils after 4 weeks of mouse treadmill exercise and assessed wound healing assay to evaluate whether treatment with exercise-activated neutrophils is effective for skeletal muscle repair in vitro. In the exercise group, significantly higher mRNA levels of maturation markers compared to the sedentary group and exercise-activated neutrophils improved wound healing of mouse muscle cells. To confirm at the human cell level, based on the well-known fact that exercise increases circulating cortisol levels, neutrophil-like cells were treated with dexamethasone (dHL60 + dex) as exercise mimetics. dHL60 + dex had significantly higher mRNA levels of neutrophil maturation marker and improved wound healing of human skeletal muscle cells compared to the control. These findings suggest that exercise affects neutrophil maturation and that exercise-induced neutrophils contribute to skeletal muscle repair in vitro.

Neutrophils in sickle cell disease: Exploring their potential role as a therapeutic target

Factors influencing the activation of neutrophils in SCD and the potential neutrophil-mediated ameliorating effects of therapies in SCD.

Targeting Neutrophil Extracellular Trap Formation: Exploring Promising Pharmacological Strategies for the Treatment of Preeclampsia

Neutrophils, which constitute the most abundant leukocytes in human blood, emerge as crucial players in the induction of endothelial cell death and the modulation of endothelial cell responses under both physiological and pathological conditions. The hallmark of preeclampsia is endothelial dysfunction induced by systemic inflammation, in which neutrophils, particularly through the formation of neutrophil extracellular traps (NETs), play a pivotal role in the development and perpetuation of endothelial dysfunction and the hypertensive state. Considering the potential of numerous pharmaceutical agents to attenuate NET formation (NETosis) in preeclampsia, a comprehensive assessment of the extensively studied candidates becomes imperative. This review aims to identify mechanisms associated with the induction and negative regulation of NETs in the context of preeclampsia. We discuss potential drugs to modulate NETosis, such as NF-κβ inhibitors, vitamin D, and aspirin, and their association with mutagenicity and genotoxicity. Strong evidence supports the notion that molecules involved in the activation of NETs could serve as promising targets for the treatment of preeclampsia.

Function and regulation of GPR84 in human neutrophils

Human neutrophils are components of the innate immune system and are the most abundant white blood cells in the circulation. They are professional phagocytes and express several G protein-coupled receptors (GPCRs), which are essential for proper neutrophil functions. So far, the two formyl peptide receptors, FPR1 and FPR2, have been the most extensively studied group of neutrophil GPCRs, but recently, a new group, the free fatty acid (FFA) receptors, has attracted growing attention. Neutrophils express two FFA receptors, GPR84 and FFA2, which sense medium- and short-chain fatty acids respectively, and display similar activation profiles. The exact pathophysiological role of GPR84 is not yet fully understood, but it is generally regarded as a pro-inflammatory receptor that mediates neutrophil activation. In this review, we summarize current knowledge of how GPR84 affects human neutrophil functions and discuss the regulatory mechanisms that control these responses, focusing on the similarities and differences in comparison to the two FPRs and FFA2. LINKED ARTICLES: This article is part of a themed issue GPR84 Pharmacology. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v181.10/issuetoc.

The post-septic peripheral myeloid compartment reveals unexpected diversity in myeloid-derived suppressor cells

Introduction

Sepsis engenders distinct host immunologic changes that include the expansion of myeloid-derived suppressor cells (MDSCs). These cells play a physiologic role in tempering acute inflammatory responses but can persist in patients who develop chronic critical illness.

Methods

Cellular Indexing of Transcriptomes and Epitopes by Sequencing and transcriptomic analysis are used to describe MDSC subpopulations based on differential gene expression, RNA velocities, and biologic process clustering.

Results

We identify a unique lineage and differentiation pathway for MDSCs after sepsis and describe a novel MDSC subpopulation. Additionally, we report that the heterogeneous response of the myeloid compartment of blood to sepsis is dependent on clinical outcome.

Discussion

The origins and lineage of these MDSC subpopulations were previously assumed to be discrete and unidirectional; however, these cells exhibit a dynamic phenotype with considerable plasticity.

Differences between human male and female neutrophils in mRNA, translation efficiency, protein, and phosphoprotein profiles

Background

Human males and females show differences in the incidence of neutrophil-associated diseases such as systemic lupus erythematosus, rheumatoid arthritis, and reactive arthritis, and differences in neutrophil physiological responses such as a faster response to the chemorepellent SLIGKV. Little is known about the basis of sex-based differences in human neutrophils.

Methods

Starting with human neutrophils from healthy donors, we used RNA-seq to examine total mRNA profiles, mRNAs not associated with ribosomes and thus not being translated, mRNAs in monosomes, and mRNAs in polysomes and thus heavily translated. We used mass spectrometry systems to identify proteins and phosphoproteins.

Results

There were sex-based differences in the translation of 24 mRNAs. There were 132 proteins with higher levels in male neutrophils; these tended to be associated with RNA regulation, ribosome, and phosphoinositide signaling pathways, whereas 30 proteins with higher levels in female neutrophils were associated with metabolic processes, proteosomes, and phosphatase regulatory proteins. Male neutrophils had increased phosphorylation of 32 proteins. After exposure to SLIGKV, male neutrophils showed a faster response in terms of protein phosphorylation compared to female neutrophils.

Conclusions

Male neutrophils have higher levels of proteins and higher phosphorylation of proteins associated with RNA processing and signaling pathways, while female neutrophils have higher levels of proteins associated with metabolism and proteolytic pathways. This suggests that male neutrophils might be more ready to adapt to a new environment, and female neutrophils might be more effective at responding to pathogens. This may contribute to the observed sex-based differences in neutrophil behavior and neutrophil-associated disease incidence and severity.

Metabolic alterations of peripheral blood immune cells and heterogeneity of neutrophil in intracranial aneurysms patients

BACKGROUND

Intracranial aneurysms (IAs) represent a severe cerebrovascular disease that can potentially lead to subarachnoid haemorrhage. Previous studies have demonstrated the involvement of peripheral immune cells in the formation and progression of IAs. Nevertheless, the impact of metabolic alterations in peripheral immune cells and changes in neutrophil heterogeneity on the occurrence and progression of IAs remains uncertain.

METHODS

Single-cell Cytometry by Time-of-Flight (CyTOF) technology was employed to profile the single-cell atlas of peripheral blood mononuclear cells (PBMCs) and polymorphonuclear cells (PMNs) in 72 patients with IAs. In a matched cohort, metabolic shifts in PBMC subsets of IA patients were investigated by contrasting the expression levels of key metabolic enzymes with their respective counterparts in the healthy control group. Simultaneously, compositional differences in peripheral blood PMNs subsets between the two groups were analysed to explore the impact of altered heterogeneity in neutrophils on the initiation and progression of IAs. Furthermore, integrating immune features based on CyTOF analysis and clinical characteristics, we constructed an aneurysm occurrence model and an aneurysm growth model using the random forest method in conjunction with LASSO regression.

RESULTS

Different subsets exhibited distinct metabolic characteristics. Overall, PBMCs from patients elevated CD98 expression and increased proliferation. Conversely, CD36 was up-regulated in T cells, B cells and monocytes from the controls but down-regulated in NK and NKT cells. The comparison also revealed differences in the metabolism and function of specific subsets between the two groups. In terms of PMNs, the neutrophil landscape within patients group revealed a pronounced shift towards heightened complexity. Various neutrophil subsets from the IA group generally exhibited lower expression levels of anti-inflammatory functional molecules (IL-4 and IL-10). By integrating clinical and immune features, the constructed aneurysm occurrence model could precisely identify patients with IAs with high prediction accuracy (AUC = 0.987). Furthermore, the aneurysm growth model also exhibited superiority over ELAPSS scores in predicting aneurysm growth (lower prediction errors and out-of-bag errors).

CONCLUSION

These findings enhanced our understanding of peripheral immune cell participation in aneurysm formation and growth from the perspectives of immune metabolism and neutrophil heterogeneity. Moreover, the predictive model based on CyTOF features holds the potential to aid in diagnosing and monitoring the progression of human IAs.

Low-Density Neutrophils Contribute to Subclinical Inflammation in Patients with Type 2 Diabetes

Type 2 diabetes (T2D) is characterized by low-grade inflammation. Low-density neutrophils (LDNs) represent normally less than 2% of total neutrophils but increase in multiple pathologies, releasing inflammatory cytokines and neutrophil extracellular traps (NETs). We assessed the count and role of high-density neutrophils (HDNs), LDNs, and NET-related activities in patients with T2D. HDNs and LDNs were purified by fluorescence-activated cell sorting (FACS) and counted by flow cytometry. Circulating inflammatory and NETs biomarkers were measured by ELISA (Enzyme Linked Immunosorbent Assay). NET formation was quantified by confocal microscopy. Neutrophil adhesion onto a human extracellular matrix (hECM) was assessed by optical microscopy. We recruited 22 healthy volunteers (HVs) and 18 patients with T2D. LDN counts in patients with diabetes were significantly higher (160%), along with circulating NETs biomarkers (citrullinated H3 histone (H3Cit), myeloperoxidase (MPO), and MPO-DNA (137%, 175%, and 69%, respectively) versus HV. Circulating interleukins (IL-6 and IL-8) and C-Reactive Protein (CRP) were significantly increased by 117%, 171%, and 79%, respectively, in patients compared to HVs. Isolated LDNs from patients expressed more H3Cit, MPO, and NETs, formed more NETs, and adhered more on hECM compared to LDNs from HVs. Patients with T2D present higher levels of circulating LDN- and NET-related biomarkers and associated pro-inflammatory activities.

Immunophenotyping of hemocytes from infected Galleria mellonella larvae as an innovative tool for immune profiling, infection studies and drug screening

In recent years, there has been a considerable increasing interest in the use of the greater wax moth Galleria mellonella as an animal model. In vivo pharmacological tests, concerning the efficacy and the toxicity of novel compounds are typically performed in mammalian models. However, the use of the latter is costly, laborious and requires ethical approval. In this context, G. mellonella larvae can be considered a valid option due to their greater ease of use and the absence of ethical rules. Furthermore, it has been demonstrated that the immune system of these invertebrates has similarity with the one of mammals, thus guaranteeing the reliability of this in vivo model, mainly in the microbiological field. To better develop the full potential of this model, we present a novel approach to characterize the hemocyte population from G. mellonella larvae and to highlight the immuno modulation upon infection and treatments. Our approach is based on the detection in isolated hemocytes from G. mellonella hemolymph of cell membrane markers typically expressed by human immune cells upon inflammation and infection, for instance CD14, CD44, CD80, CD163 and CD200. This method highlights the analogies between G. mellonella larvae and humans. Furthermore, we provide an innovative tool to perform pre-clinical evaluations of the efficacy of antimicrobial compounds in vivo to further proceed with clinical trials and support drug discovery campaigns.

PVB exerts anti-inflammatory effects by inhibiting the activation of MAPK and NF-κB signaling pathways and ROS generation in neutrophils

Pinaverium bromide (PVB) has been shown to protect mice against sepsis, which is predominantly attributed to PVB-mediated anti-inflammatory effects by inhibiting primed neutrophils to produce proinflammatory cytokines. However, the underlying mechanism(s) by which PVB affects neutrophils remains unknown. In this study, we report that treatment with PVB either before or after LPS stimulation attenuated IL-1β and TNF-α expression at both mRNA and protein levels in LPS-activated murine neutrophils. Further experiments revealed that PVB inhibited the phosphorylation of ERK, JNK, and IκBα in LPS-stimulated murine neutrophils. Moreover, PVB reduced reactive oxygen species (ROS) levels via regulating NADPH oxidase 2 (NOX2) activity, as represented by inhibiting p47phox translocation from the cytoplasm to the cellular membrane. Importantly, PVB significantly attenuated IL-1β, TNF-α, IL-6, CXCL1 production in both LPS-stimulated low density neutrophils (LDNs) and normal density neutrophils (NDNs) isolated from septic patients. Collectively, we demonstrated that PVB exerts anti-inflammatory effect by attenuating ROS generation and suppressing the activation of MAPK and NF-κB signaling pathways, suggesting that PVB may act as a potential therapeutic agent for sepsis by inhibiting neutrophil priming and activation.

Phenotypic and Functional Diversity of Neutrophils in Gut Inflammation and Cancer

Neutrophils [polymorphonuclear leukocytes (PMNs)] execute important effector functions protecting the host against invading pathogens. However, their activity in tissue can exacerbate inflammation and inflammation-associated tissue injury and tumorigenesis. Until recently, PMNs were considered to be short-lived, terminally differentiated phagocytes. However, this view is rapidly changing with the emerging evidence of increased PMN lifespan in tissues, PMN plasticity, and phenotypic heterogeneity. Specialized PMN subsets have been identified in inflammation and in developing tumors, consistent with both beneficial and detrimental functions of PMNs in these conditions. Because PMN and tumor-associated neutrophil activity and the resulting beneficial/detrimental impacts primarily occur after homing to inflamed tissue/tumors, studying the underlying mechanisms of PMN/tumor-associated neutrophil trafficking is of high interest and clinical relevance. This review summarizes some of the key findings from over a decade of work from my laboratory and others on the regulation of PMN recruitment and identification of phenotypically and functionally diverse PMN subtypes as they pertain to gut inflammation and colon cancer.

Differences in gene expression profiles in early and late stage rhodesiense HAT individuals in Malawi

T. b. rhodesiense is the causative agent of Rhodesian human African trypanosomiasis (r-HAT) in Malawi. Clinical presentation of r-HAT in Malawi varies between foci and differs from East African HAT clinical phenotypes. The purpose of this study was to gain more insights into the transcriptomic profiles of patients with early stage 1 and late stage 2 HAT disease in Malawi. Whole blood from individuals infected with T. b. rhodesiense was used for RNA-Seq. Control samples were from healthy trypanosome negative individuals matched on sex, age range, and disease foci. Illumina sequence FASTQ reads were aligned to the GRCh38 release 84 human genome sequence using HiSat2 and differential analysis was done in R Studio using the DESeq2 package. XGR, ExpressAnalyst and InnateDB algorithms were used for functional annotation and gene enrichment analysis of significant differentially expressed genes. RNA-seq was done on 23 r-HAT case samples and 28 healthy controls with 7 controls excluded for downstream analysis as outliers. A total of 4519 genes were significant differentially expressed (p adjusted <0.05) in individuals with early stage 1 r-HAT disease (n = 12) and 1824 genes in individuals with late stage 2 r-HAT disease (n = 11) compared to controls. Enrichment of innate immune response genes through neutrophil activation was identified in individuals with both early and late stages of the disease. Additionally, lipid metabolism genes were enriched in late stage 2 disease. We further identified uniquely upregulated genes (log2 Fold Change 1.4-2.0) in stage 1 (ZNF354C) and stage 2 (TCN1 and MAGI3) blood. Our data add to the current understanding of the human transcriptome profiles during T. b. rhodesiense infection. We further identified biological pathways and transcripts enriched than were enriched during stage 1 and stage 2 r-HAT. Lastly, we have identified transcripts which should be explored in future research whether they have potential of being used in combination with other markers for staging or r-HAT.

Neutrophil nucleus: shaping the past and the future

Neutrophils are innate immune cells that are key to protecting the host against infection and maintaining body homeostasis. However, if dysregulated, they can contribute to disease, such as in cancer or chronic autoinflammatory disorders. Recent studies have highlighted the heterogeneity in the neutrophil compartment and identified the presence of immature neutrophils and their precursors in these pathologies. Therefore, understanding neutrophil maturity and the mechanisms through which they contribute to disease is critical. Neutrophils were first characterized morphologically by Ehrlich in 1879 using microscopy, and since then, different technologies have been used to assess neutrophil maturity. The advances in the imaging field, including state-of-the-art microscopy and machine learning algorithms for image analysis, reinforce the use of neutrophil nuclear morphology as a fundamental marker of maturity, applicable for objective classification in clinical diagnostics. New emerging approaches, such as the capture of changes in chromatin topology, will provide mechanistic links between the nuclear shape, chromatin organization, and transcriptional regulation during neutrophil maturation.

Neutrophil extracellular traps enhance S. aureus skin colonization by oxidative stress induction and downregulation of epidermal barrier genes

Staphylococcus aureus is the most common cause of bacterial skin infections in humans, including patients with atopic dermatitis (AD). Polymorphonuclear neutrophils (PMNs) are the first cells to infiltrate an infection site, where they usually provide an effective first line of defense, including neutrophil extracellular trap (NET) formation. Here, we show that infiltrating PMNs in inflamed human and mouse skin enhance S. aureus skin colonization and persistence. Mechanistically, we demonstrate that a crosstalk between keratinocytes and PMNs results in enhanced NET formation upon S. aureus infection, which in turn induces oxidative stress and expression of danger-associated molecular patterns such as high-mobility-group-protein B1 (HMGB1) in keratinocytes. In turn, HMGB1 enhances S. aureus skin colonization and persistence by promoting skin barrier dysfunctions by the downregulation of epidermal barrier genes. Using patient material, we show that patients with AD exhibit enhanced presence of PMNs, NETs, and HMGB1 in the skin, demonstrating the clinical relevance of our finding.

Experimental procedures for flow cytometry of wild-type mouse brain: a systematic review

Objective

The aim of this study was to systematically review the neuroimmunology literature to determine the average immune cell counts reported by flow cytometry in wild-type (WT) homogenized mouse brains.

Background

Mouse models of gene dysfunction are widely used to study age-associated neurodegenerative disorders, including Alzheimer's disease and Parkinson's disease. The importance of the neuroimmune system in these multifactorial disorders has become increasingly evident, and methods to quantify resident and infiltrating immune cells in the brain, including flow cytometry, are necessary. However, there appears to be no consensus on the best approach to perform flow cytometry or quantify/report immune cell counts. The development of more standardized methods would accelerate neuroimmune discovery and validation by meta-analysis.

Methods

There has not yet been a systematic review of 'neuroimmunology' by 'flow cytometry' via examination of the PROSPERO registry. A protocol for a systematic review was subsequently based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) using the Studies, Data, Methods, and Outcomes (SDMO) criteria. Literature searches were conducted in the Google Scholar and PubMed databases. From that search, 900 candidate studies were identified, and 437 studies were assessed for eligibility based on formal exclusion criteria.

Results

Out of the 437 studies reviewed, 58 were eligible for inclusion and comparative analysis. Each study assessed immune cell subsets within homogenized mouse brains and used flow cytometry. Nonetheless, there was considerable variability in the methods, data analysis, reporting, and results. Descriptive statistics have been presented on the study designs and results, including medians with interquartile ranges (IQRs) and overall means with standard deviations (SD) for specific immune cell counts and their relative proportions, within and between studies. A total of 58 studies reported the most abundant immune cells within the brains were TMEM119+ microglia, bulk CD4+ T cells, and bulk CD8+ T cells.

Conclusion

Experiments to conduct and report flow cytometry data, derived from WT homogenized mouse brains, would benefit from a more standardized approach. While within-study comparisons are valid, the variability in methods of counting of immune cell populations is too broad for meta-analysis. The inclusion of a minimal protocol with more detailed methods, controls, and standards could enable this nascent field to compare results across studies.

The Immunophenotypic Profile of Healthy Human Bone Marrow

Flow cytometry enables multiparametric characterization of hematopoietic cell immunophenotype. Deviations from normal immunophenotypic patterns comprise a cardinal feature of many hematopoietic neoplasms, underscoring the ongoing essentiality of flow cytometry as a diagnostic tool. However, understanding of aberrant hematopoiesis requires an equal understanding of normal hematopoiesis as a comparator. In this review, we outline key features of healthy adult hematopoiesis and lineage specification as illuminated by flow cytometry and provide diagrams illustrating what a diagnostician may observe in flow cytometric plots. These features provide a profile of baseline hematopoiesis, to which clinical samples with suspected neoplasia may be compared.

A synthetic metastatic niche reveals antitumor neutrophils drive breast cancer metastatic dormancy in the lungs

Biomaterial scaffolds mimicking the environment in metastatic organs can deconstruct complex signals and facilitate the study of cancer progression and metastasis. Here we report that a subcutaneous scaffold implant in mouse models of metastatic breast cancer in female mice recruits lung-tropic circulating tumor cells yet suppresses their growth through potent in situ antitumor immunity. In contrast, the lung, the endogenous metastatic organ for these models, develops lethal metastases in aggressive breast cancer, with less aggressive tumor models developing dormant lungs suppressing tumor growth. Our study reveals multifaceted roles of neutrophils in regulating metastasis. Breast cancer-educated neutrophils infiltrate the scaffold implants and lungs, secreting the same signal to attract lung-tropic circulating tumor cells. Second, antitumor and pro-tumor neutrophils are selectively recruited to the dormant scaffolds and lungs, respectively, responding to distinct groups of chemoattractants to establish activated or suppressive immune environments that direct different fates of cancer cells.

Low-density granulocytes are related to shorter pregnancy duration but not to interferon alpha protein blood levels in systemic lupus erythematosus

BACKGROUND

An increased risk of pregnancy complications is seen in women with systemic lupus erythematosus (SLE), but the specific immunopathological drivers are still unclear. Hallmarks of SLE are granulocyte activation, type I interferon (IFN) overproduction, and autoantibodies. Here we examined whether low-density granulocytes (LDG) and granulocyte activation increase during pregnancy, and related the results to IFNα protein levels, autoantibody profile, and gestational age at birth.

METHODS

Repeated blood samples were collected during pregnancy in trimesters one, two, and three from 69 women with SLE and 27 healthy pregnant women (HC). Nineteen of the SLE women were also sampled late postpartum. LDG proportions and granulocyte activation (CD62L shedding) were measured by flow cytometry. Plasma IFNα protein concentrations were quantified by single molecule array (Simoa) immune assay. Clinical data were obtained from medical records.

RESULTS

Women with SLE had higher LDG proportions and increased IFNα protein levels compared to HC throughout pregnancy, but neither LDG fractions nor IFNα levels differed during pregnancy compared to postpartum in SLE. Granulocyte activation status was higher in SLE relative to HC pregnancies, and it was increased during pregnancy compared to after pregnancy in SLE. Higher LDG proportions in SLE were associated with antiphospholipid positivity but not to IFNα protein levels. Finally, higher LDG proportions in trimester three correlated independently with lower gestational age at birth in SLE.

CONCLUSION

Our results suggest that SLE pregnancy results in increased peripheral granulocyte priming, and that higher LDG proportions late in pregnancy are related to shorter pregnancy duration but not to IFNα blood levels in SLE.

Integrative analysis of risk factors for immune-related adverse events of checkpoint blockade therapy in cancer

Immune-related adverse events (irAEs) induced by checkpoint inhibitors involve a multitude of different risk factors. Here, to interrogate the multifaceted underlying mechanisms, we compiled germline exomes and blood transcriptomes with clinical data, before and after checkpoint inhibitor treatment, from 672 patients with cancer. Overall, irAE samples showed a substantially lower contribution of neutrophils in terms of baseline and on-therapy cell counts and gene expression markers related to neutrophil function. Allelic variation of HLA-B correlated with overall irAE risk. Analysis of germline coding variants identified a nonsense mutation in an immunoglobulin superfamily protein, TMEM162. In our cohort and the Cancer Genome Atlas (TCGA) data, TMEM162 alteration was associated with higher peripheral and tumor-infiltrating B cell counts and suppression of regulatory T cells in response to therapy. We developed machine learning models for irAE prediction, validated using additional data from 169 patients. Our results provide valuable insights into risk factors of irAE and their clinical utility.

New cell sources for CAR-based immunotherapy

Chimeric antigen receptor (CAR) T cell therapy, in which a patient's own T lymphocytes are engineered to recognize and kill cancer cells, has achieved striking success in some hematological malignancies in preclinical and clinical trials, resulting in six FDA-approved CAR-T products currently available in the market. Despite impressive clinical outcomes, concerns about treatment failure associated with low efficacy or high cytotoxicity of CAR-T cells remain. While the main focus has been on improving CAR-T cells, exploring alternative cellular sources for CAR generation has garnered growing interest. In the current review, we comprehensively evaluated other cell sources rather than conventional T cells for CAR generation.

Immunomodulation of neutrophil granulocyte functions by bacterial polyphosphates

Polyphosphates are highly conserved, linear polymers of monophosphates that reside in all living cells. Bacteria produce long chains containing hundreds to thousands of phosphate units, which can interfere with host defense to infection. Here, we report that intratracheal long-chain polyphosphate administration to C57BL/6J mice resulted in the release of proinflammatory cytokines and influx of Ly6G+ polymorphonuclear neutrophils in the bronchoalveolar lavage fluid causing a disruption of the physiologic endothelial-epithelial small airway barrier and histologic signs of lung injury. Polyphosphate-induced effects were attenuated after neutrophil depletion in mice. In isolated murine neutrophils, long-chain polyphosphates modulated cytokine release induced by lipopolysaccharides (LPS) from Gram-negative bacteria or lipoteichoic acid from Gram-positive bacteria. In addition, long-chain polyphosphates induced immune evasive effects in human neutrophils. In detail, long-chain polyphosphates downregulated CD11b and curtailed the phagocytosis of Escherichia coli particles by neutrophils. Polyphosphates modulated the migration capacity by inducing CD62L shedding resulting in CD62Llow and CD11blow neutrophils. The release of IL-8 induced by LPS was also significantly reduced. Pharmacologic blockade of PI3K with wortmannin antagonized long-chain polyphosphate-induced effects on LPS-induced IL-8 release. In conclusion, polyphosphates govern immunomodulation in murine and human neutrophils, suggesting polyphosphates as a therapeutic target for bacterial infections to restore innate immune defense.

A Brief Overview of Neutrophils in Neurological Diseases

Neutrophils are the most abundant leukocyte in circulation and are the first line of defense after an infection or injury. Neutrophils have a broad spectrum of functions, including phagocytosis of microorganisms, the release of pro-inflammatory cytokines and chemokines, oxidative burst, and the formation of neutrophil extracellular traps. Traditionally, neutrophils were thought to be most important for acute inflammatory responses, with a short half-life and a more static response to infections and injury. However, this view has changed in recent years showing neutrophil heterogeneity and dynamics, indicating a much more regulated and flexible response. Here we will discuss the role of neutrophils in aging and neurological disorders; specifically, we focus on recent data indicating the impact of neutrophils in chronic inflammatory processes and their contribution to neurological diseases. Lastly, we aim to conclude that reactive neutrophils directly contribute to increased vascular inflammation and age-related diseases.

DNA Hypomethylation Is Associated with Increased Inflammation in Peripheral Blood Neutrophils of Children with Autism Spectrum Disorder: Understanding the Role of Ubiquitous Pollutant Di(2-ethylhexyl) Phthalate

Autism spectrum disorder (ASD) is a multidimensional disorder in which environmental, immune, and genetic factors act in concert to play a crucial role. ASD is characterized by social interaction/communication impairments and stereotypical behavioral patterns. Epigenetic modifications are known to regulate genetic expression through various mechanisms. One such mechanism is DNA methylation, which is regulated by DNA methyltransferases (DNMTs). DNMT transfers methyl groups onto the fifth carbon atom of the cytosine nucleotide, thus converting it into 5-methylcytosine (5mC) in the promoter region of the DNA. Disruptions in methylation patterns of DNA are usually associated with modulation of genetic expression. Environmental pollutants such as the plasticizer Di(2-ethylhexyl) phthalate (DEHP) have been reported to affect epigenetic mechanisms; however, whether DEHP modulates DNMT1 expression, DNA methylation, and inflammatory mediators in the neutrophils of ASD subjects has not previously been investigated. Hence, this investigation focused on the role of DNMT1 and overall DNA methylation in relation to inflammatory mediators (CCR2, MCP-1) in the neutrophils of children with ASD and typically developing healthy children (TDC). Further, the effect of DEHP on overall DNA methylation, DNMT1, CCR2, and MCP-1 in the neutrophils was explored. Our results show that the neutrophils of ASD subjects have diminished DNMT1 expression, which is associated with hypomethylation of DNA and increased inflammatory mediators such as CCR2 and MCP-1. DEHP further causes downregulation of DNMT1 expression in the neutrophils of ASD subjects, probably through oxidative inflammation, as antioxidant treatment led to reversal of a DEHP-induced reduction in DNMT1. These data highlight the importance of the environmental pollutant DEHP in the modification of epigenetic machinery such as DNA methylation in the neutrophils of ASD subjects.

Single-cell dissection of human hematopoietic reconstitution after allogeneic hematopoietic stem cell transplantation

Hematopoietic stem cell transplantation is an effective regenerative therapy for many malignant, inherited, or autoimmune diseases. However, our understanding of reconstituted hematopoiesis in transplant patients remains limited. Here, we uncover the reconstitution dynamics of human allogeneic hematopoietic stem and progenitor cells (HSPCs) at single-cell resolution after transplantation. Transplanted HSPCs underwent rapid and measurable changes during the first 30 days after transplantation, characterized by a strong proliferative response on the first day. Transcriptomic analysis of HSPCs enabled us to observe that immunoregulatory neutrophil progenitors expressing high levels of the S100A gene family were enriched in granulocyte colony-stimulating factor-mobilized peripheral blood stem cells. Transplant recipients who developed acute graft-versus-host disease (aGVHD) infused fewer S100A^high immunoregulatory neutrophil progenitors, immunophenotyped as Lin^-CD34⁺CD66b⁺CD177⁺, than those who did not develop aGVHD. Therefore, our study provides insights into the regenerative process of transplanted HSPCs in human patients and identifies a potential criterion for identifying patients at high risk for developing aGVHD early after transplant.

Putative Role of Neutrophil Extracellular Trap Formation in Chronic Myeloproliferative Neoplasms

Myeloproliferative neoplasms (MPNs) are hematologic malignancies characterized by gene mutations that promote myeloproliferation and resistance to apoptosis via constitutively active signaling pathways, with Janus kinase 2-signal transducers and the activators of transcription (JAK-STAT) axis as a core part. Chronic inflammation has been described as a pivot for the development and advancement of MPNs from early stage cancer to pronounced bone marrow fibrosis, but there are still unresolved questions regarding this issue. The MPN neutrophils are characterized by upregulation of JAK target genes, they are in a state of activation and with deregulated apoptotic machinery. Deregulated neutrophil apoptotic cell death supports inflammation and steers them towards secondary necrosis or neutrophil extracellular trap (NET) formation, a trigger of inflammation both ways. NETs in proinflammatory bone marrow microenvironment induce hematopoietic precursor proliferation, which has an impact on hematopoietic disorders. In MPNs, neutrophils are primed for NET formation, and even though it seems obvious for NETs to intervene in the disease progression by supporting inflammation, no reliable data are available. We discuss in this review the potential pathophysiological relevance of NET formation in MPNs, with the intention of contributing to a better understanding of how neutrophils and neutrophil clonality can orchestrate the evolution of a pathological microenvironment in MPNs.

Increased levels of low density neutrophils (LDNs) in myocardial infarction

BACKGROUND

Recent evidence suggests that neutrophils are highly plastic cells that can display heterogeneous phenotypes. Low-density neutrophils (LDNs) have been described in many inflammatory conditions, and are thought to represent an immature, hyperactivated subtype of neutrophils. Neutrophils are significantly involved in the inflammatory response to myocardial infarction (MI), although we do not know the extent to which LDNs exist, or function, in MI. This study sought to determine the frequency and phenotype of LDNs in MI patients, compared to healthy subjects (HS).

METHODS

LDNs and normal-density neutrophils (NDNs) were isolated from the peripheral blood of MI subjects (n = 12) and HSs (n = 12) using density gradient centrifugation. LDNs and NDNs were analysed by flow cytometry to identify neutrophils (CD66b⁺CD15⁺CD14^-CD3^-CD19^- cells) and examine neutrophil activation (CD11b, CD66b and CD15) and maturity (CD33 and CD16).

RESULTS

We identified LDNs within the peripheral blood mononuclear cell (PBMC) fraction of blood, and this population is significantly enriched in MI patients (1.04 ± 0.75% of PBMCs), compared to HS (0.29 ± 0.24%, p = .003). Across both cohorts, LDNs express significantly higher levels of CD66b and CD15, indicating a heightened state of activation compared to NDNs. In this study, LDNs were described as CD33^highCD16^low, compared to CD33^lowCD16^high NDNs, indicating the immaturity of this neutrophil subtype.

CONCLUSIONS

An increase in the frequency of hyperactivated, immature LDNs is an immunological feature of MI. We highlight a potential pathological role of LDNs in MI, which underscores the need to expand our current understanding of this subtype in MI and other cardiovascular diseases (CVDs).

The effect of SMAD4 on the prognosis and immune response in hypopharyngeal carcinoma

Objectives

In malignant tumors, elevated infiltration of intratumoral CD8+ cytotoxic T cells predicts a beneficial prognosis, whereas high levels of CD15+ neutrophils in peritumor tissues indicate poor prognosis. It is unclear how SMAD4, which promotes favorable clinical outcomes and antitumor immunoregulation, along with CD8+ cytotoxic T cells and CD15+ neutrophils exert an influence on hypopharyngeal carcinoma (HPC).

Materials and methods

Specimens were collected from 97 patients with HPC. Immunohistological analyses of SMAD4, CD8+ cytotoxic T cell and CD15+ neutrophil expression were performed. SMAD4 nuclear intensity was measured, meanwhile, CD8+ cytotoxic T cells and CD15+ neutrophils were counted under a microscope. The prognostic role of SMAD4 was determined using the log-rank test and univariate and multivariate analyses. The relationship among SMAD4, CD8+ cytotoxic T cells, and CD15+ neutrophils was estimated by Mann-Whitney U test.

Results

High levels of SMAD4 were associated with favorable overall survival (OS) and disease-free survival (DFS) in HPC. Multivariate analysis suggested that SMAD4 is an independent predictor of OS and DFS. A high density of intratumoral CD8+ cytotoxic T cells and low accumulation of CD15+ neutrophils in the peritumor area were associated with longer OS and DFS. Furthermore, SMAD4 was linked to the levels of intratumoral CD8+ cytotoxic T cells and peritumoral CD15+ neutrophils. Patients with high SMAD4/high intratumoral CD8+ cytotoxic T cells or high SMAD4/low peritumoral CD15+ neutrophils showed the best prognosis.

Conclusion

SMAD4, CD8+ cytotoxic T cell level, and CD15+ neutrophil level have prognostic value in HPC. SMAD4 is a promising prognostic marker reflecting immune response in HPC.

Current knowledge on the early stages of human neutropoiesis

Polymorphonuclear neutrophils are no longer considered as a homogeneous population of terminally differentiated and short-lived cells that belong to the innate immune system only. In fact, data from the past decades have uncovered that neutrophils exhibit large phenotypic heterogeneity and functional versatility that render them more plastic than previously thought. Hence, their precise role as effector cells in inflammation, in immune response and in other pathophysiological processes, including tumors, needs to be better evaluated. In such a complex scenario, common knowledge of the differentiation of neutrophils in bone marrow refers to lineage precursors, starting from the still poorly defined myeloblasts, and proceeding sequentially to promyelocytes, myelocytes, metamyelocytes, band cells, segmented neutrophils, and mature neutrophils, with each progenitor stage being more mature and better characterized. Thanks to the development and utilization of cutting-edge technologies, novel information about neutrophil precursors at stages earlier than the promyelocytes, hence closer to the hematopoietic stem cells, is emerging. Accordingly, this review discusses the main findings related to the very early precursors of human neutrophils and provides our perspectives on human neutropoiesis.

Comparative flow cytometry-based immunophenotyping analysis of peripheral blood leukocytes before and after fixation with paraformaldehyde

Flow cytometry based immunophenotyping provides prime insight into cellular population composition and characteristics, and is widely used in basic and clinical research. Challenges in processing peripheral blood samples in a timely manner necessitate protocol adaptations and utilization of fixatives. Fixation, however, may introduce artifacts to the flow cytometry readout. We performed a comparative flow cytometry immunophenotyping analysis of 13 immune cell populations in the whole blood using a staining protocol with and without fixation step. Freshly procured human peripheral blood samples were stained with a panel of 33 fluorochrome-conjugated antibodies. Samples were processed using a protocol with or without a paraformaldehyde-based fixation step, and matching sample pairs were analyzed by flow cytometry. Our results show that paraformaldehyde-based fixation, in comparison to matched unfixed samples, did not significantly affect population distribution and frequency for: B cells, Plasmablasts, Dendritic cells, NK cells, Granulocytes, Neutrophils, Eosinophils, or Hematopoietic Stem/Progenitor Cells. However, fixation led to significant marker shifts in the subpopulation distribution in CD4, T regulatory, CD8, Monocytes, and Basophils. These results indicate the importance of pre-experimental assessment of fixation-introduced artifacts in the flow cytometry output when considering the feasibility of fresh processing. This is especially important for samples analyzed using comprehensive exploratory immunoprofiling panels.

Comparative diagnostic accuracy between simplified and original flow cytometric gating strategies for peripheral blood neutrophil myeloperoxidase expression in ruling out myelodysplastic syndromes

Background

Flow cytometric analysis of peripheral blood neutrophil myeloperoxidase expression is accurate in ruling out myelodyplastic syndromes (MDS) but might not be suitable for implementation in busy clinical laboratories. We aimed to simplify the original gating strategy and examine its accuracy.

Methods

Using the individual data from 62 consecutive participants enrolled in a prospective validation study, we assessed the agreement in intra-individual robust coefficient of variation (RCV) of peripheral blood neutrophil myeloperoxidase expression and compared diagnostic accuracy between the simplified and original gating strategies.

Results

Cytomorphological evaluation of bone marrow aspirate confirmed MDS in 23 patients (prevalence, 37%), unconfirmed MDS in 32 patients (52%), and was uninterpretable in 7 patients (11%). Median intra-individual RCV for simplified and original gating strategies were 30.7% (range, 24.7–54.4) and 30.6% (range, 24.7–54.1), with intra-class correlation coefficient quantifying absolute agreement equal to 1.00 (95% confidence interval [CI], 0.99 to 1.00). The areas under the receiver operating characteristic (ROC) curves were 0.93 (95% CI, 0.82–0.98) and 0.92 (95% CI, 0.82–0.98), respectively (P = .32). Using simplified or original gating strategy, intra-individual RCV values lower than a pre-specified threshold of 30.0% ruled out MDS for 35% (19 of 55) patients, with both sensitivity and negative predictive value estimates of 100%.

Conclusions

The simplified gating strategy performs as well as the original one for ruling out MDS and has the potential to save time and reduce resource utilization. Yet, prospective validation of the simplified gating strategy is warranted before its adoption in routine.

Trial registration

ClinicalTrials.gov Identifier: NCT03363399 (First posted on December 6, 2017).

Neutrophil Extracellular Traps in Asthma: Friends or Foes?

Asthma is a chronic inflammatory disease characterized by variable airflow limitation and airway hyperresponsiveness. A plethora of immune and structural cells are involved in asthma pathogenesis. The roles of neutrophils and their mediators in different asthma phenotypes are largely unknown. Neutrophil extracellular traps (NETs) are net-like structures composed of DNA scaffolds, histones and granular proteins released by activated neutrophils. NETs were originally described as a process to entrap and kill a variety of microorganisms. NET formation can be achieved through a cell-death process, termed NETosis, or in association with the release of DNA from viable neutrophils. NETs can also promote the resolution of inflammation by degrading cytokines and chemokines. NETs have been implicated in the pathogenesis of various non-infectious conditions, including autoimmunity, cancer and even allergic disorders. Putative surrogate NET biomarkers (e.g., double-strand DNA (dsDNA), myeloperoxidase-DNA (MPO-DNA), and citrullinated histone H3 (CitH3)) have been found in different sites/fluids of patients with asthma. Targeting NETs has been proposed as a therapeutic strategy in several diseases. However, different NETs and NET components may have alternate, even opposite, consequences on inflammation. Here we review recent findings emphasizing the pathogenic and therapeutic potential of NETs in asthma.

Extracellular vesicles from pristane-treated CD38-deficient mice express an anti-inflammatory neutrophil protein signature, which reflects the mild lupus severity elicited in these mice

In CD38-deficient (Cd38-/-) mice intraperitoneal injection of pristane induces a lupus-like disease, which is milder than that induced in WT mice, showing significant differences in the inflammatory and autoimmune processes triggered by pristane. Extracellular vesicles (EV) are present in all body fluids. Shed by cells, their molecular make-up reflects that of their cell of origin and/or tissue pathological situation. The aim of this study was to analyze the protein composition, protein abundance, and functional clustering of EV released by peritoneal exudate cells (PECs) in the pristane experimental lupus model, to identify predictive or diagnostic biomarkers that might discriminate the autoimmune process in lupus from inflammatory reactions and/or normal physiological processes. In this study, thanks to an extensive proteomic analysis and powerful bioinformatics software, distinct EV subtypes were identified in the peritoneal exudates of pristane-treated mice: 1) small EV enriched in the tetraspanin CD63 and CD9, which are likely of exosomal origin; 2) small EV enriched in CD47 and CD9, which are also enriched in plasma-membrane, membrane-associated proteins, with an ectosomal origin; 3) small EV enriched in keratins, ECM proteins, complement/coagulation proteins, fibrin clot formation proteins, and endopetidase inhibitor proteins. This enrichment may have an inflammation-mediated mesothelial-to-mesenchymal transition origin, representing a protein corona on the surface of peritoneal exudate EV; 4) HDL-enriched lipoprotein particles. Quantitative proteomic analysis allowed us to identify an anti-inflammatory, Annexin A1-enriched pro-resolving, neutrophil protein signature, which was more prominent in EV from pristane-treated Cd38-/- mice, and quantitative differences in the protein cargo of the ECM-enriched EV from Cd38-/- vs WT mice. These differences are likely to be related with the distinct inflammatory outcome shown by Cd38-/- vs WT mice in response to pristane treatment. Our results demonstrate the power of a hypothesis-free and data-driven approach to transform the heterogeneity of the peritoneal exudate EV from pristane-treated mice in valuable information about the relative proportion of different EV in a given sample and to identify potential protein markers specific for the different small EV subtypes, in particular those proteins defining EV involved in the resolution phase of chronic inflammation.

Flow cytometry lyophilised-reagent tube for quantifying peripheral blood neutrophil myeloperoxidase expression in myelodysplastic syndromes (MPO-MDS-Develop): protocol for a diagnostic accuracy study

INTRODUCTION

Suspicion of myelodysplastic syndromes (MDS) is the most common reason for bone marrow aspirate in elderly patients. Peripheral blood neutrophil myeloperoxidase expression quantified by flow cytometric analysis might rule out MDS for up to 35% of patients referred for suspected disease, without requiring bone marrow aspiration. Yet laboratory-developed liquid antibody cocktails have practical limitations, because of lack of standardisation and poor stability. This research project aims to estimate the level of agreement and comparative accuracy between a single-use flow cytometry tube of lyophilised reagents (BD Lyotube Stain 468) and its laboratory-developed liquid reagent counterpart in quantifying peripheral blood neutrophil myeloperoxidase expression, among adult patients referred for suspected MDS.

METHODS AND ANALYSIS

The MPO-MDS-Develop project is a cross-sectional diagnostic accuracy study of two index tests by comparison with a reference standard in consecutive unselected adult patients conducted at a single university hospital. Flow cytometry analysis of peripheral blood samples will be performed by independent operators blinded to the reference diagnosis, using either Lyotube Stain 468 or laboratory-developed liquid reagent cocktail. The reference diagnosis of MDS will be established by cytomorphological evaluation of bone marrow aspirate by two independent haematopathologists blinded to the index test results. Morphologic assessment will be complemented by bone marrow flow cytometric score, karyotype and targeted next-generation sequencing panel of 43 genes, where relevant. The target sample size is 103 patients.

ETHICS AND DISSEMINATION

An institutional review board (Comité de Protection des Personnes Sud Est III, Lyon, France) approved the protocol prior to study initiation (reference number: 2020-028-B). Participants will be recruited using an opt-out approach. Efforts will be made to release the primary results within 6 months of study completion.

TRIAL REGISTRATION NUMBER

NCT04399018.

Roles of tumor-associated neutrophils in tumor metastasis and its clinical applications

Metastasis, a primary cause of death in patients with malignancies, is promoted by intrinsic changes in both tumor and non-malignant cells in the tumor microenvironment (TME). As major components of the TME, tumor-associated neutrophils (TANs) promote tumor progression and metastasis through communication with multiple growth factors, chemokines, inflammatory factors, and other immune cells, which together establish an immunosuppressive TME. In this review, we describe the potential mechanisms by which TANs participate in tumor metastasis based on recent experimental evidence. We have focused on drugs in chemotherapeutic regimens that target TANs, thereby providing a promising future for cancer immunotherapy.

Tigecycline Suppresses the Virulence Factors of Multidrug-Resistant Acinetobacter baumannii Allowing Human Neutrophils to Act

Purpose

To determine the ability of human neutrophils to kill multidrug-resistant Acinetobacter baumannii (MDRAB) in the presence of tigecycline (TGC).

Methods

Clinical isolates of MDRAB were cultured with human neutrophils and H₂O₂ in the presence of TGC. The numbers of viable bacteria, catalase activity, gene expression at the K locus of the MDRAB, reactive oxygen species (ROS) production, and granule exocytosis in human neutrophils were determined.

Results

There was a time-dependent increase in the numbers of MDRAB after co-culturing with human neutrophils, whereas there was a significant decrease in the MDRAB numbers when co-cultured with both, human neutrophils and TGC for 6 h. The presence or absence of TGC did not affect total ROS production or the expression of CD11b, CD15, and CD63 on human neutrophils occurred when co-cultured with MDRAB. TGC significantly suppressed catalase activity and gene expression at the K locus of MDRAB, and significantly reduced the thickness of the capsule. Additionally, the bacterial viability of TGC-treated MDRAB cultured with H₂O₂ was lower than that without H₂O₂ after 6 h of culture.

Conclusion

TGC significantly suppressed the expression of catalase and the capsule in MDRAB without adverse effects on neutrophil function, allowing human neutrophils to kill MDRAB. TGC is an effective antibiotic for treating MDRAB infections.