The Neutrophil

Buprofezin causes early developmental toxicity of zebrafish (Danio rerio) embryos: morphological, physiological and biochemical responses

Buprofezin (BPFN), a pesticide used to control crop pests and diseases, causes potential harm to aquatic animals and the environment by leaching into aquatic ecosystems. However, there are limited studies on the toxicity of BPFN to aquatic organisms. Using zebrafish embryos, we integrated flow cytometry, qRT-PCR, RNA-seq and other techniques to assess BPFN's developmental toxicity. Additionally, IBRv2 index and Mantel test correlation were applied to comprehensively evaluate the developmental toxicity of BPFN. The results showed that BPFN induced cytotoxicity, including increased reactive oxygen species levels, mitochondrial membrane potential depolarization, and apoptosis, which further resulted in developmental toxicity of zebrafish embryos such as delayed hatching, reduced survival rate, and severe morphological deformities. BPFN also affected the number and distribution of immune cells, resulting in immunotoxicity, and disrupted the endogenous antioxidant system by altering the activities of catalase, superoxide dismutase, and glutathione S-transferase and contents of malondialdehyde and glutathione. Gene expression analysis revealed that BPFN induced changes in the expression of genes associated with oxidative stress, apoptosis, inflammation, swim bladder development, and eye development. In the comprehensive evaluation, BPFN showed the strongest developmental toxic effect in the 20 μM BPFN-treated group at 48 hpf, and there was the significant correlation between embryonic development, oxidative stress, apoptosis, and inflammatory response. The rescue experiment confirmed that astaxanthin can alleviate the embryonic developmental toxicity caused by BPFN to a certain extent. In summary, BPFN induced early developmental toxicity in zebrafish embryos, which might be associated with mitochondria-mediated apoptosis pathway induced by oxidative stress.

NETosis: A key player in autoimmunity, COVID-19, and long COVID

NETosis, the process through which neutrophils release neutrophil extracellular traps (NETs), has emerged as a crucial mechanism in host defense and the pathogenesis of autoimmune responses. During the SARS-CoV-2 pandemic, this process received significant attention due to the central role of neutrophil recruitment and activation in infection control. However, elevated neutrophil levels and dysregulated NET formation have been linked to coagulopathy and endothelial damage, correlating with disease severity and poor prognosis in COVID-19. Moreover, it is known that SARS-CoV-2 can induce persistent low-grade systemic inflammation, known as long COVID, although the underlying causes remain unclear. It has been increasingly acknowledged that excessive NETosis and NET generation contribute to further pathophysiological abnormalities following SARS-CoV-2 infection. This review provides an updated overview of the role of NETosis in autoimmune diseases, but also the relationship between COVID-19 and long COVID with autoimmunity (e.g., latent and overt autoimmunity, molecular mimicry, epitope spreading) and NETosis (e.g., immune responses, NET markers). Finally, we discuss potential therapeutic strategies targeting dysregulated NETosis to mitigate the severe complications of COVID-19 and long COVID.

A prognostic nomogram for patients with III-IV nasopharyngeal carcinoma based on dynamic changes in the inflammatory and nutrition index

BACKGROUND

The purpose of the study was to explore the value of dynamic changes in inflammatory and nutritional index after comprehensive treatment in patients with stage III-IVA nasopharyngeal carcinoma (NPC). A prognostic model was also established and validated for progression-free survival (PFS) of patients.

METHODS

We retrospectively selected 279 NPC patients with stage III-IVA. Their general clinical data and hematological index were collected and then calculated the changes during treatment. X-tile software was used to determine the optimal cut-off value. COX regression, Lasso method, and Boruta method were used to variable selection and model establishment. Using the bootstrap internal validation method, concordance index (C-index), calibration plot, and Kaplan-Meier curves were used to evaluate the model. To test the prognostic value of the model, we have also evaluated the performance of the nomogram against a conventional tumor metastasis staging system (TNM).

RESULTS

Multivariable COX regression analysis demonstrated that clinical staging, delta lymphocyte, delta monocyte, delta albumin, delta platelet-to-lymphocyte ratio and delta systemic immune inflammation index were related to the PFS of NPC patients. The C-index of the model was 0.712, and the calibration curve indicated that the model had good consistency. The C-index of the TNM staging system was 0.597, which was considerably lower compared to our model (P = 0.015).

CONCLUSION

We demonstrated the predictive value of dynamic changes in inflammatory and nutritional indices for the prognosis of NPC by successfully establishing and validating a prognostic model for predicting 1- and 3-year PFS after comprehensive treatment in patients with stage III-IVA NPC.

Immune-based strategies for the treatment of biofilm infections

Biofilms are bacterial communities surrounded by a polymeric matrix that can form on implanted materials and biotic surfaces, resulting in chronic infection that is recalcitrant to immune- and antibiotic-mediated clearance. Therefore, biofilm infections present a substantial clinical challenge, as treatment often involves additional surgical interventions to remove the biofilm nidus, prolonged antimicrobial therapy to clear residual bacteria, and considerable risk of treatment failure or infection recurrence. These factors, combined with progressive increases in antimicrobial resistance, highlight the need for alternative therapeutic strategies to circumvent undue morbidity, mortality, and resource strain on the healthcare system resulting from biofilm infections. One promising option is reprogramming dysfunctional immune responses elicited by biofilm. Here, we review the literature describing immune responses to biofilm infection with a focus on targets or strategies ripe for clinical translation. This represents a complex and dynamic challenge, with context-dependent host-pathogen interactions that differ across infection models, microenvironments, and individuals. Nevertheless, consistencies among these variables exist, which could facilitate the development of immune-based strategies for the future treatment of biofilm infections.

A light-regulated circadian timer optimizes neutrophil bactericidal activity to boost daytime immunity

The immune response exhibits strong circadian rhythmicity, with enhanced bacterial clearance often synchronized with an organism's active phase. Despite providing the bulk of cellular antibacterial defense, the neutrophil clockwork is poorly understood. Here, we used larval zebrafish to explore the role of clock genes in neutrophils during infection. Per2 was required in neutrophils for reactive oxygen species (ROS) production and bacterial killing by enhancing infection-responsive expression of high-mobility group box 1a (hmgb1a). The Cry binding domain of Per2 was required for regulation of neutrophil bactericidal activity, and neutrophils lacking Cry1a had elevated bactericidal activity and infection-responsive hmgb1a expression. A conserved cis-regulatory element with BMAL1 and nuclear factor κB binding motifs gated infection-responsive hmgb1a expression to the light phase. Mutagenesis of the BMAL1 motif in neutrophils blunted the priming effect of light on bactericidal activity and hmgb1a expression. These findings identify a light-responsive cell-intrinsic timer that controls time-of-day variations in antibacterial activity.

Neutrophils secrete exosome-associated DNA to resolve sterile acute inflammation

Acute inflammation, characterized by a rapid influx of neutrophils, is a protective response that can lead to chronic inflammatory diseases when left unresolved. We previously showed that secretion of LTB4-containing exosomes via nuclear envelope-derived multivesicular bodies is required for effective neutrophil infiltration during inflammation. Here we report that the co-secretion of these exosomes with nuclear DNA facilitates the resolution of the neutrophil infiltrate in a mouse skin model of sterile inflammation. Activated neutrophils exhibit rapid and repetitive DNA secretion as they migrate directionally using a mechanism distinct from suicidal neutrophil extracellular trap release and cell death. Packaging of DNA in the lumen of nuclear envelope-multivesicular bodies is mediated by lamin B receptor and chromatin decondensation. These findings advance our understanding of neutrophil functions during inflammation and the physiological relevance of DNA secretion.

Recombination of miR-146b by Lactococcus lactis for Remolding Macrophages and the Microbiome in the Treatment of Murine Colitis

MicroRNA 146b (miR-146b) mitigates the progression of inflammatory bowel disease (IBD) by reprogramming macrophage polarization through the induction of interleukin-10 (IL-10), thereby eliciting an anti-inflammatory response, but its application is currently hindered by the lack of safe delivery systems that allow sustained miR-146b expression. Inspired by the probiotic Lactococcus lactis, which can produce extracellular vesicles (EVs) that carry a variety of biomolecules, we successfully constructed a genetically modified L. lactis strain that expresses miR-146b (LL-miR-146b) in a nisin-dependent manner and found that its administration eliminated intestinal inflammation in a murine IBD model. Furthermore, LL-miR-146b remodeled the proinflammatory microenvironment, enhanced the integrity of the intestinal barrier, and manipulated the gut microbiota. We then confirmed that the LL-miR-146b-induced reduction in intestinal inflammation was partially dependent on EVs that contained miR-146b, which modulated the activation of classically activated macrophages (M1 macrophages). Importantly, this treatment showed no significant systemic toxicity. In conclusion, we developed a safe and effective vector for IBD treatment by integrating a strategy for calming cytokine storms with biotherapy.

Equipotent bisphenol S and bisphenol F with widely differing modes of action exhibit additive effects in immunotoxicity: insights based on intrinsic immunity, apoptosis and regeneration, and oxidative stress

Bisphenol S (BPS) and Bisphenol F (BPF), as alternatives to bisphenol A (BPA), are recognized for their endocrine-disrupting properties, but their combined immune toxicity mechanisms remain poorly understood. This study systematically evaluates the individual and joint immune toxicity effects of BPS and BPF through ADMET predictions, transgenic zebrafish models, and molecular docking analyses. The results indicate that equal effect concentration BPS and BPF act through distinct immune pathways: BPS primarily targets macrophages to mediate immune responses, while BPF significantly stimulates neutrophil proliferation and induces a stronger inflammatory response through chemokine signaling. Molecular docking studies show that BPF binds more stably to pro-apoptotic protein Mapk8 and oxidative stress-related protein Hsp90aa1, leading to significantly higher levels of apoptosis and reactive oxygen species (ROS) compared to BPS. The similarity of modes of action (MOA)between BPS and BPF based on relevant immune indicators calculated and experimentally is about 0.3; this quantitative result also proves that modes of action differ widely. Nonetheless, most of the indicators showed superimposed effects in the combined experiments, and it is noteworthy that the oxidative stress indicators (SOD, MDA) showed synergistic effects, suggesting that BPS and BPF, which have very different modes of action, are able to be risk assessed using an additive model with respect to immunity, but may exhibit synergistic risks with respect to oxidative stress. This research demonstrates that BPS and BPF induce immune toxicity via different molecular targets and pathways and highlights the need to account for their synergistic effects in risk assessments. These findings provide important insights into the immune toxicity mechanisms of BPA substitutes and the potential risks of combined exposures.

Dual-membrane bioinspired nanocarriers for targeted therapy of MRSA-induced acute lung injury and bacteremia

Bioinspired nanoparticles enhance the targeting of specific organs by facilitating interactions and communication at the nano-bio interface. Combining human neutrophil and lung epithelial cell membranes for nanoparticle cloaking offers distinct advantages in binding to bacteria and pulmonary epithelium, thus targeting infection-induced inflammatory areas. This study aimed to develop rifampicin-loaded biomimetic nanocarriers by wrapping a polymeric core with dual membranes derived from neutrophils and A549 cells, inheriting the membrane characteristics of the native cells. To evaluate the therapeutic efficacy of these nanocarriers, methicillin-resistant Staphylococcus aureus (MRSA)-induced acute lung injury (ALI) and bacteremia models were established in mice. The hybrid membrane-coated nanoparticles exhibited an average diameter of 191 nm and a nearly neutral surface charge of -2.7 mV. Zeta potential measurements, gel electrophoresis, and scanning electron microscopy (SEM) confirmed the successful decoration of the membranes on the nanoparticles. The dual membrane-coated nanoparticles were readily and rapidly ingested by lung epithelial cells within five minutes, demonstrating superior cellular uptake compared to those coated with a single membrane. SEM analysis showed significant adherence of the hybrid membrane-coated nanoparticles to the MRSA surface. The rifampicin-loaded nanocarriers effectively eradicated MRSA in its planktonic, biofilm, and intracellular forms. In vivo biodistribution studies in ALI mice revealed that the hybrid membrane-coated nanoparticles effectively targeted inflamed lungs, showing a two-fold increase in lung accumulation compared to the unfunctionalized nanoparticles. This targeted delivery significantly reduced the severity of lung damage caused by ALI and bacteremia, including MRSA burden, cytokine/chemokine expression, alveolar edema, and immune cell infiltration. The bioinspired nanocarriers improved the pulmonary targeting of inflamed sites and neutralized the proinflammatory mediators and toxins in the injured lung. No significant toxicity was observed in the healthy mice receiving the nanocarriers. Thus, targeted biomimetic nanocarriers, utilizing antibacterial and anti-inflammatory strategies, show promising benefits for treating pulmonary injury.

Differences in uterine and serum metabolome associated with clinical cure failure of metritis in dairy cows†

This study investigated differences in uterine and serum metabolome associated with clinical cure failure of metritis in dairy cows. Metritis was diagnosed in lactating Holstein cows from two Florida dairies and defined by the presence of fetid, watery, reddish-brown vaginal discharge from 4 to 12 days postpartum (dpp). Cows with metritis (n = 24) were paired with cows without metritis of similar parity and dpp (n = 24). On the day of metritis diagnosis (day 0), all cows with metritis received antimicrobial therapy. The continued presence of the fetid, watery, reddish-brown discharge on day 5 (n = 16) was defined as clinical cure failure, whereas clinical cure was defined by its absence (n = 8). Metabolome analyses of uterine lavage (days 0 and 5) and serum samples (day 0) were conducted using untargeted gas chromatography time-of-flight mass spectrometry. Normalized data were analyzed using partial least squares-discriminant analysis and ANOVA, adjusting P-values for multiple comparisons. Differences in the uterine metabolome on day 0 associated with clinical cure failure were linked to carbohydrate, amino acid, and lipid metabolism. Greater concentrations of arachidonic acid, ribose, and glutaric acid were associated with clinical cure failure, suggesting a greater degree of tissue lesion and inflammation. No differences in the serum metabolome were associated with cure failure. No differences in uterine metabolome were associated with clinical cure failure on day 5. The findings suggest that clinical cure failure is associated with a greater uterine inflammatory process that did not persist until cure assessment day.

Differences between human male and female neutrophils with respect to which RNAs are present in polysomes

Background

Human males and females show differences in the incidence of neutrophil-associated diseases such as systemic lupus erythematosus, rheumatoid arthritis, and multiple sclerosis, and differences in neutrophil physiological responses such as responses to infection, tissue damage, and chemotactic factors. However, 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 RNA profiles, RNAs not associated with ribosomes and thus not being translated, RNAs in monosomes, and RNAs in polysomes and thus heavily translated.

Results

There were sex-based differences in the levels of RNAs across free RNA, monosome, and polysome fractions. Male neutrophils had increased levels of mRNAs encoding mitochondrial proteins in the free RNA fractions, indicating low levels of translation. The polysomes of male neutrophils were enriched for mRNAs encoding cytoskeletal organization, cell motility, and cell activation. The polysomes of female neutrophils were enriched for mRNAs associated the regulation of metabolic processes, cytokine responses, and mitochondrial proteins.

Conclusions

These data indicate that male and female neutrophils have different expression patterns and different translation efficiency of some mRNAs. This may contribute to the observed sex-based differences in neutrophil behavior and neutrophil-associated disease incidence and severity.

Matrix-producing neutrophils populate and shield the skin

Defence from environmental threats is provided by physical barriers that confer mechanical protection and prevent the entry of microorganisms1. If microorganisms overcome those barriers, however, innate immune cells use toxic chemicals to kill the invading cells2,3. Here we examine immune diversity across tissues and identify a population of neutrophils in the skin that expresses a broad repertoire of proteins and enzymes needed to build the extracellular matrix. In the naive skin, these matrix-producing neutrophils contribute to the composition and structure of the extracellular matrix, reinforce its mechanical properties and promote barrier function. After injury, these neutrophils build 'rings' of matrix around wounds, which shield against foreign molecules and bacteria. This structural program relies on TGFβ signalling; disabling the TGFβ receptor in neutrophils impaired ring formation around wounds and facilitated bacterial invasion. We infer that the innate immune system has evolved diverse strategies for defence, including one that physically shields the host from the outside world.

Guardians Turned Culprits: NETosis and Its Influence on Pulmonary Fibrosis Development

Idiopathic pulmonary fibrosis (IPF) is a debilitating, life-threatening irreversible lung disease characterized by the excessive accumulation of fibrotic tissue in the lungs, impairing their function. The exact mechanisms underlying Pulmonary fibrosis (PF) are multifaceted and not yet fully understood. Reports show that during COVID-19 pandemic, PF was dramatically increased due to the hyperactivation of the immune system. Neutrophils and macrophages are the patrolling immune cells that keep the microenvironment balanced. Neutrophil extracellular traps (NETs) are a normal protective mechanism of neutrophils. The chief components of the NETs include DNA, citrullinated histones, and anti-microbial peptides which are released by the activated neutrophils. However, it is becoming increasingly evident that hyperactivation of immune cells can also turn into criminals when it comes to pathological state. Dysregulated NETosis may contribute to sustained inflammation, overactivation of fibroblasts, and ultimately promoting collagen deposition which is the characteristic feature of PF. The role of NETs along with inflammation is attaining greater attention. However, seldom researches are related to the relationship between NETs causing PF. This review highlights the cellular mechanism of NETs-induced pulmonary fibrosis, which could give a better understanding of molecular targets which may be helpful for treating NETs-induced PF.

Recent Advances in Immunothrombosis and Thromboinflammation

Inflammation and thrombosis are traditionally considered two separate entities of acute host responses to barrier breaks. While inciting inflammatory responses is a prerequisite to fighting invading pathogens and subsequent restoration of tissue homeostasis, thrombus formation is a crucial step of the hemostatic response to prevent blood loss following vascular injury. Though originally designed to protect the host, excessive induction of either inflammatory signaling or thrombus formation and their reciprocal activation contribute to a plethora of disorders, including cardiovascular, autoimmune, and malignant diseases. In this state-of-the-art review, we summarize recent insights into the intricate interplay of inflammation and thrombosis. We focus on the protective aspects of immunothrombosis as well as evidence of detrimental sequelae of thromboinflammation, specifically regarding recent studies that elucidate its pathophysiology beyond coronavirus disease 2019 (COVID-19). We introduce recently identified molecular aspects of key cellular players like neutrophils, monocytes, and platelets that contribute to both immunothrombosis and thromboinflammation. Further, we describe the underlying mechanisms of activation involving circulating plasma proteins and immune complexes. We then illustrate how these factors skew the inflammatory state toward detrimental thromboinflammation across cardiovascular as well as septic and autoimmune inflammatory diseases. Finally, we discuss how the advent of new technologies and the integration with clinical data have been used to investigate the mechanisms and signaling cascades underlying immunothrombosis and thromboinflammation. This review highlights open questions that will need to be addressed by the field to translate our mechanistic understanding into clinically meaningful therapeutic targeting.

Coronin 1a-mediated F-actin disassembly controls effector function in murine neutrophils

The double-edged role of neutrophils in effective host defense and harmful pathology is an emerging topic in clinical research. Neutrophils release highly potent antimicrobial granule compounds and reactive oxygen species (ROS) that can also be detrimental to the host and promote inflammatory diseases and cancer. Here we show that disassembly of F-actin greatly facilitates ROS production and degranulation in neutrophils. Utilizing neutrophils from Coronin 1a (Coro1a)-deficient mice, our data reveal that the actin-regulatory protein Coro1a controls this spatial F-actin deconstruction and concomitantly forms a signaling complex with Rac-GTPases, thereby promoting activation and translocation of Rac to the membrane during neutrophil activation. This functional activity of Coro1a was critical for neutrophil granule exocytosis and the activation of the NADPH oxidase complex. Consistent with these findings, impaired ROS production in Coro1a-deficient neutrophils was rescued by pharmacological promotion of actin depolymerization or activation of Rac. Together, our findings suggest that the Coro1a/Rac signaling hub acts as a central regulatory element that coordinates actin cytoskeletal reorganization required for the execution of neutrophil effector functions. Since Coro1a is highly conserved between mice and humans and associated with human immunodeficiency, our results are also relevant for human biomedical studies.

Senescent neutrophils: a hidden role in cancer progression

Neutrophils have recently received increased attention in cancer because they contribute to all stages of cancer. Neutrophils are so far considered to have a short half-life. However, a growing body of literature has shown that tumor-associated neutrophils (TANs) acquire a prolonged lifespan. This review discusses recent work surrounding the mechanisms by which neutrophils can persist in the tumor microenvironment (TME). It also highlights different scenarios for therapeutic targeting of protumorigenic neutrophils, supporting the idea that, in tumors, inhibition of neutrophil recruitment is not sufficient because these cells can persist and remain hidden from current interventions. Hence, the elimination of long-lived neutrophils should be pursued to increase the efficacy of standard therapy.

Advances in neutrophil extracellular traps and ferroptosis in sepsis-induced cardiomyopathy

Sepsis-induced cardiomyopathy is a reversible non-ischemic acute cardiac dysfunction associated with sepsis. It is strongly associated with an abnormal immune response. It emerges as a vital threat to public health owing to its high mortality rate. However, the exact pathogenesis requires further investigation. In recent years, NETosis and ferroptosis, which are novel modes of programmed cell death, have been identified and found to play important roles in sepsis-related organ damage. This article outlines the mechanisms of these two modes of cell death, discusses the role of neutrophil extracellular traps in myocardial injury and the importance of ferroptosis in sepsis-induced cardiomyopathy, and reviews the potential interconnection between these two types of programmed cell death in sepsis-induced cardiomyopathy.

Neutrophil single-cell analysis identifies a type II interferon-related subset for predicting relapse of autoimmune small vessel vasculitis

To identify the dynamics of neutrophil autoimmunity, here we focus on anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis and perform single-cell transcriptome and surface proteome analyses on peripheral white blood cells from patients with new-onset microscopic polyangiitis (MPA). Compared with controls, two neutrophil populations, immature neutrophils and neutrophils with type II interferon signature genes (Neu_T2ISG), are increased in patients with MPA. Trajectory and cell-cell interaction analyses identify Neu_T2ISG as a subset that differentiates from mature neutrophils upon stimulation with IFN-γ and TNF, which synergize to induce myeloperoxidase and Fcγ receptors expression on the neutrophil cell surface and promote ANCA-induced neutrophil extracellular trap formation. Case-by-case analysis indicates that patients with a high proportion of the Neu_T2ISG subset are associated with persistent vasculitis symptoms. A larger cohort analysis shows that serum IFN-γ levels at disease onset correlate with susceptibility to disease relapse. Our findings thus identify neutrophil diversity at the single cell level and implicate a biomarker for predicting relapse in small vessel vasculitis.

Characterizing a low-density neutrophil gene signature in acute and chronic infections and its impact on disease severity

Low-density neutrophils (LDNs) or polymorphonuclear myeloid-derived suppressor cells are involved in the pathogenesis of cancer, autoimmune, and infectious diseases. They are crucial in the host response to invading pathogens, especially during acute illness, and are associated with poor prognosis in many infectious diseases. However, their gene expression profile and contribution to disease outcomes are not well described. We conducted a meta-analysis of gene expression datasets from peripheral blood mononuclear cells (PBMCs), focusing on patients with viral and bacterial infections. We identified a consensus set of 2,798 differentially expressed genes. Among these, 49 genes were commonly found in both the neutrophil degranulation pathway and the granule lumen-specific community. To validate this signature, we evaluated its expression in RNA-seq datasets, finding consistent upregulation of 24 genes in severe infections, 17 of them overlapped with genes overexpressed in CD16int cells. We also investigated the abundance of LDN-related proteins in a PBMC proteomics dataset from a cohort of sepsis and septic shock patients. Out of the 17 genes analyzed, 13 corresponding proteins were identified, 10 of which demonstrated significantly higher abundance in sepsis and septic shock patients compared with healthy controls. In conclusion, our study identified a pattern of 17 upregulated LDN genes, common to PBMC transcriptome and RNA-seq, and upregulated in CD16int, associated with acute infections and severe clinical outcomes, marking the first time these genes have been collectively presented as a potential signature of LDNs in relation to disease severity. Further research with prospective cohorts is needed to validate this LDN signature and explore its clinical implications.

High-dimensional spectral flow cytometry of activation and phagocytosis by peripheral human polymorphonuclear leukocytes

Polymorphonuclear leukocytes (PMNs) are terminally differentiated phagocytes with pivotal roles in infection, inflammation, tissue injury, and resolution. PMNs display a breadth of responses to diverse endogenous and exogenous stimuli, making understanding of these innate immune responders vital yet challenging to achieve. Here, we report a 22-color spectral flow cytometry panel to profile primary human PMNs for surface marker expression of activation, degranulation, phagocytosis, migration, chemotaxis, and interaction with fluorescently labeled cargo. We demonstrate the surface marker response of PMNs to phorbol ester stimulation compared with untreated controls in an adherent PMN model with additional analysis of intra- and inter-subject variability. PMNs challenged with the Gram-negative bacterial pathogen Neisseria gonorrhoeae revealed infectious dose-dependent changes in surface marker expression in bulk, population-level analysis. Imaging flow cytometry complemented spectral cytometry, demonstrating that fluorescence signal from labeled bacteria corresponded with bacterial burden on a per-cell basis. Spectral flow cytometry subsequently identified surface markers, which varied with direct PMN-bacterium association as well as those which varied in the presence of bacteria but without phagocytosis. This spectral panel protocol highlights best practices for efficient customization and is compatible with downstream approaches such as spectral cell sorting and single-cell RNA-sequencing for applicability to diverse research questions in the field of PMN biology.

Targeting neutrophil extracellular traps in cancer progression and metastasis

Neutrophils serve as pivotal effectors and regulators of the intricate immune system. Their contributions are indispensable, encompassing the obliteration of pathogens and a significant role in both cancer initiation and progression. Conversely, malignancies profoundly affect neutrophil activity, maturation, and lifespans. Cancer cells manipulate their biology to enhance or suppress the key functions of neutrophils. This manipulation is one of the most remarkable defensive mechanisms used by neutrophils, including the formation of neutrophil extracellular traps (NETs). NETs are filamentous structures comprising DNA, histones, and proteins derived from cytotoxic granules. In this review, we discuss the bidirectional interplay in which cancer elicits NET formation, and NETs concurrently facilitate cancer progression. Here, we discuss how vascular dysfunction and thrombosis induced by neutrophils and NETs contribute to an elevated risk of mortality from cardiovascular complications in patients with cancer. Ultimately, we propose a series of therapeutic strategies that hold promise for effectively targeting NETs in clinical settings.

Proteomic Profiles of Neutrophils from Behcet's Uveitis Patients and their Sex Differences

Behcet's uveitis (BU) is one of the most vision-threatening uveitis entities with male-biased incidence and severity. Neutrophil dysfunction has been implicated in the pathogenesis of this disease. However, their proteomic changes are not completely understood. We performed proteomic analysis on peripheral neutrophils from patients with active BU and identified 82 up-regulated and 516 down-regulated differentially expressed proteins (DEPs) compared to healthy controls (HCs). We further performed functional analysis on these DEPs and found that the pathway involved in neutrophil extracellular trap formation was activated, whereas nucleotide metabolism and apoptosis were suppressed. Compared with female patients, male patients presented enhanced pathways associated neutrophil-mediated inflammatory responses and suppressed apoptosis. Additionally, integrative analysis of proteomic profiles and single-cell RNA sequencing (scRNA-seq) data revealed that these sex differences might be related to the enhanced inflammatory response in primed inflammatory and inflammatory neutrophils as well as deficiencies in apoptosis and nucleotide metabolism in ROS-responsive neutrophils. Collectively, our data revealed the proteomic profiles of neutrophils from patients with BU, and their functional changes may play crucial roles in the pathogenesis of this disease and its sex differences.

Exploring TLR agonists as adjuvants for COVID-19 oral vaccines

The COVID-19 pandemic underscored the importance of advancing technologies that enable the rapid development and distribution of more effective vaccines when required. Since SARS-CoV-2 enters the body through the nasal mucosa, optimising the induction of secretory IgA (sIgA) production, a key component of the mucosal immune response, is essential. It has long been known that the induction of sIgA occurs when a vaccine is administered through mucosal surfaces and the immune responses initiated at one mucosal site can influence immune activity at other mucosal surfaces. Consequently, we propose an oral vaccine formulation (Vacform) comprising the immunomodulator CL097, a TLR7/8 agonist, and the SARS-CoV-2 spike protein, both encapsulated within glucan particles (GPs). The studies demonstrated that Vacform induced ROS production in RAW 264.7 cells but not in human neutrophils. The concentrations of Vacform tested did not induce NO production in RAW 264.7 cells. While Vacform stimulated the production of TNF-α and IL-6 in mouse spleen cells, this effect was not observed in RAW 264.7 cells. Finally, Vacform stimulated the proliferation of human PBMCs. Thus, its immunomodulatory properties were evident in specific cells under certain in vitro conditions. The Vacform was subsequently tested in vaccination studies. C57BL/6 mice were initially immunized subcutaneously, followed by two oral boosts with Vacform every two weeks. The Vacform elicited both, humoral (serum IgG and mucosal sIgA) and cellular immune responses. A balanced Th1/Th2/Th17 immune profile was observed. In conclusion, the GPs:CL097 adjuvant system shows promise for eliciting robust immune responses against SARS-CoV-2 and provides a foundation for future studies on dose-response optimization and challenge models.

Cathelicidin antimicrobial peptides mediate immune protection in marsupial neonates

Marsupial neonates are born with immature immune systems, making them vulnerable to pathogens. While neonates receive maternal protection, they can also independently combat pathogens, although the mechanisms remain unknown. Using the sugar glider (Petaurus breviceps) as a model, we investigated immunological defense strategies of marsupial neonates. Cathelicidins-a family of antimicrobial peptides expanded in the genomes of marsupials-are highly expressed in developing neutrophils. Sugar glider cathelicidins reside in two genomic clusters, and their coordinated expression is achieved by enhancer sharing within clusters and long-range physical interactions between clusters. Functionally, cathelicidins modulate immune responses and have potent antibacterial effects, sufficient to provide protection in a mouse model of sepsis. Evolutionarily, cathelicidins have a complex history, with marsupials and monotremes uniquely retaining both clusters among tetrapods. Thus, cathelicidins are critical mediators of marsupial immunity, and their evolution may reflect the life history-specific immunological needs of these animals.

Cytokine-mediated regulation of immune cell metabolic pathways in the tumor microenvironment

Cancer, an important global health problem, is defined by aberrant cell proliferation and continues to be the main cause of death globally. The tumor microenvironment (TME) plays an essential role in the development of cancer, resistance to therapy, and regulation of the immune response. Some immune cells in the TME, like T cells, B cells, macrophages, dendritic cells, and natural killer cells, can either stop or help tumor growth, depending on how metabolic and cytokine changes happen. Cytokines function as essential signaling molecules that modulate immune cell metabolism, altering their functionality. This review focuses on how cytokine-mediated metabolic reprogramming affects the activity of immune cells inside the TME, which can either make the immune response stronger or weaker. New ways of treating cancer that focus on metabolic pathways and cytokine signaling, such as using IL (Interleukin) - 15, IL- 10, and IL- 4, show promise in boosting immune cell activity and making cancer treatments more effective. Finding these pathways could lead to new ways to treat cancer with immunotherapy that focus on metabolic competition and immune resistance in the TME.

Interaction of low-density neutrophils with other immune cells in the mechanism of inflammation

Low-density neutrophils (LDNs) are a unique subpopulation of neutrophils, play a significant role in regulating innate and adaptive immunity in various inflammation-related diseases. Emerging evidence suggests that LDNs play a significant role in the pathogenesis and progression of various diseases, including infections, autoimmune disorders, and cancer. In this review, we address the origin, development, and heterogeneity of LDNs, and the roles of LDNs in system homeostasis and diseases. We will focus on the findings of the interaction between LDNs and other immune cells. We will then discuss potential novel therapeutic strategies of intervention in diseases by targeting LDNs.

The crosstalk of monocyte-neutrophil in hair follicles regulates neutrophil transepidermal migration in contact dermatitis

The excessive accumulation of neutrophils within the epidermis is a significant hallmark of cutaneous diseases; however, the mechanisms governing neutrophil transepidermal migration (NTEM) remain inadequately understood. In this study, we develop trichromatic-fluorescence-labeled chimeric mice by utilizing Cx3cr1GFP/+Lyz2RFP/+ mice as bone marrow donors and Krt14YFP/+ mice as recipients. This approach enables us to visualize the process of NTEM and the crosstalk between neutrophils and monocytes in a murine model of irritant contact dermatitis (ICD). Intravital imaging reveals a preferential transmigration of neutrophils through hair follicle (HF), where dermal neutrophils exhibit limited mobility and interact with dermal monocytes. Notably, 18 h following hapten exposure, dermal neutrophils continuously migrate toward HF regions and form clusters within 3 h. Importantly, MMP-9 is identified as essential for the NTEM process; the depletion of dermal monocytes results in a significant reduction of MMP-9 expression in the skin and inhibits the NTEM process in ICD. Mechanistically, dermal monocytes are found to be a crucial source of the cytokines TNF-α and CXCL2, which promote the upregulation of MMP-9 in neutrophils. Therefore, our results highlight HF regions as crucial gateways for dermal monocyte-modulated NTEM and provide visual insights into the crosstalk between neutrophils and monocytes in inflammatory skin disorders.

The dual role of IL-17 in periodontitis regulating immunity and bone homeostasis

Periodontitis is a common dysbiotic bacteria-induced inflammatory disease characterized by alveolar bone resorption, leading to tooth loss. Interleukin-17 (IL-17) is a critical cytokine with dual roles in periodontium, which exerts the function of host defense, including neutrophil recruitment, phagocytosis, and mucosal immunity. However, excessive expression of IL-17 causes persistent chronic inflammation, local tissue breakdown, and bone loss. This review highlights the protective and pathological functions of IL-17 on immunity and bone homeostasis in inflammatory bone-related diseases. We also provide the latest findings with IL-17 knockout mice in periodontitis and highlight complex immune responses under various experimental models. This may provide a critical perception of inflammatory bone-related disease management using an immune-modulating strategy.

MPO and its role in cancer, cardiovascular and neurological disorders: An update

Myeloperoxidase (MPO) is an enzyme that contains a heme group, found mostly in neutrophils and in small amounts in monocytes and plays a major role in their anti-microbial activity. However, excessive levels of MPO have been linked to various disorders and identified as a major cause of tissue destruction. Inhibiting its activity can reduce the severity and extent of tissue damage. Over activity of MPO during chronic inflammation has been shown to be involved in tumorigenesis by inducing a hyper-mutagenic environment through oxidant interaction with DNA, causing DNA modification. Vascular endothelium is one of the most important targets of MPO and high levels have been associated with increased rates of cardiomyopathy, ischemic stroke, heart failure, myocardial infarction, and atrial fibrillation. Therefore, it may be considered a therapeutic target in the treatment of cardiovascular disorders. MPO also participates in the pathogenesis of neurodegenerative diseases. For example, an increase in MPO levels has been observed in the brain tissue of patients with Alzheimer's, Multiple sclerosis (MS), and Parkinson's diseases. In Alzheimer's disease, active MPO is mostly found in the location of beta amyloids and microglia. Therefore, targeting MPO may be a potential treatment and prevention strategy for neurological disorders. This review will discuss MPO's physiological and pathological role in cancer, cardiovascular, and neurological disorders.

Neutrophilic inflammation in bronchiectasis

Noncystic fibrosis bronchiectasis, hereafter referred to as bronchiectasis, is a chronic, progressive lung disease that can affect people of all ages. Patients with clinically significant bronchiectasis have chronic cough and sputum production, as well as recurrent respiratory infections, fatigue and impaired health-related quality of life. The pathophysiology of bronchiectasis has been described as a vicious vortex of chronic inflammation, recurring airway infection, impaired mucociliary clearance and progressive lung damage that promotes the development and progression of the disease. This review describes the pivotal role of neutrophil-driven inflammation in the pathogenesis and progression of bronchiectasis. Delayed neutrophil apoptosis and increased necrosis enhance dysregulated inflammation in bronchiectasis and failure to resolve this contributes to chronic, sustained inflammation. The excessive release of neutrophil serine proteases, such as neutrophil elastase, cathepsin G and proteinase 3, promotes a protease-antiprotease imbalance that correlates with increased inflammation in bronchiectasis and contributes to disease progression. While there are currently no licensed therapies to treat bronchiectasis, this review will explore the evolving evidence for neutrophilic inflammation as a novel treatment target with meaningful clinical benefits.

The Interplay Between Innate Immunity and Nonimmune Cells in Lung Damage, Inflammation, and Repair

As the site of gas exchange, the lung is critical for organismal survival. It is also subject to continual environmental insults inflicted by pathogens, particles, and toxins. Sometimes, these insults result in structural damage and the initiation of an innate immune response. Operating in parallel, the immune response aims to eliminate the threat, while the repair process ensures continual physiological function of the lung. The inflammatory response and repair processes are thus inextricably linked in time and space but are often studied in isolation. Here, we review the interplay of innate immune cells and nonimmune cells during lung insult and repair. We highlight how cellular cross talk can fine-tune the circuitry of the immune response, how innate immune cells can facilitate or antagonize proper organ repair, and the prolonged changes to lung immunity and physiology that can result from acute immune responses and repair processes.

The Integrated Pulmonary Immune Response to Pneumonia

Pneumonia is an acute respiratory infection of the lower respiratory tract. The effectiveness of the host immune response determines the severity of infection, or whether pneumonia occurs at all. The lungs house both innate and adaptive immune systems, which integrate their activities to provide host defense that eliminates microbes and prevents lower respiratory infection from becoming severe. Professional immune cells in the lung, like macrophages and lymphocytes, work with lung constituents, like epithelial cells and fibroblasts, to optimize antimicrobial defense. The dynamics of the immune response during infection and the immune components contributing to defense are influenced by prior experiences with respiratory pathogens, remodeling lung immunity in ways that improve responses against subsequent infections. This review covers how innate and adaptive immune activities coordinate inside the lung to provide integrated and effective immune resistance against respiratory pathogens.

Differences Between Unstimulated and Stimulated Human Male and Female Neutrophils in Protein and Phosphoprotein Profiles

Human males and females show differences in the incidence of neutrophil-associated diseases and differences in neutrophil responses such as a faster response to the chemorepellent Ser-Leu-Ile-Gly-Lys-Val-NH2 (SLIGKV) in males. Little is known about the basis of sex-based differences in human neutrophils. We used mass spectrometry to identify proteins and phosphoproteins in unstimulated human neutrophils and in neutrophils incubated with the SLIGKV, a protease-activated receptor 2 agonist. There were 132 proteins with higher levels in unstimulated male neutrophils; these proteins tended to be associated with RNA regulation, ribosome, and phosphoinositide signaling pathways, whereas 30 proteins with higher levels in unstimulated female neutrophils were associated with metabolic processes, proteasomes, and phosphatase regulatory proteins. Unstimulated male neutrophils had increased phosphorylation of 32 proteins compared to females. After exposure to SLIGKV, male neutrophils showed a faster response in terms of protein phosphorylation compared to female neutrophils. Male neutrophils have higher levels of proteins and higher phosphorylation of proteins associated with RNA processing and signaling pathways. 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.

Therapeutic Black Phosphorus Nanosheets Elicit Neutrophil Response for Enhanced Tumor Suppression

Black phosphorus (BP) has demonstrated potential as a drug carrier and photothermal agent in cancer therapy; however, its intrinsic functions in cancer treatment remain underexplored. This study investigates the immunomodulatory effects of polyethylene glycol-functionalized BP (BP-PEG) nanosheets in breast cancer models. Using immunocompetent mouse models-including 4T1 orthotopic BALB/c mice and MMTV-PyMT transgenic mice, it is found that BP-PEG significantly inhibits tumor growth and metastasis without directly inducing cytotoxicity in tumor cells. Mass cytometry analysis reveals that BP-PEG reshapes the tumor immune microenvironment by recruiting neutrophils. Neutrophil depletion experiments further demonstrate that the antitumor effects of BP-PEG are dependent on neutrophils. Moreover, bulk and single-cell RNA sequencing indicate that BP-PEG is mainly taken up by macrophages, leading to the release of inflammatory factors such as IL1A and CXCL2, which enhance neutrophil recruitment and activation, thereby amplifying the antitumor immune response. Finally, co-culture assays confirm that BP-PEG indeed enhances the antitumor activity of neutrophils and natural killer (NK) cells. These findings position BP-PEG as an immunomodulatory agent capable of reprogramming the tumor microenvironment to promote innate immunity against breast cancer. By stimulating neutrophil-mediated antitumor activity, BP-PEG offers a unique therapeutic approach that can potentially enhance the efficacy of existing cancer immunotherapies.

Development and validation of a neutrophil extracellular traps-related gene signature for lower-grade gliomas

There is growing evidence linking neutrophil extracellular traps (NETs) to tumor genesis, growth, distant metastasis, and tumor-related thrombosis. However, the roles of NETs-related genes (NETRGs) on LGG prognosis remain unclear. The purpose of this study was to integrate multiple machine learning techniques and experiment validation to develop a reliable NETs-based signature that opens up novel approaches for assessing the prognosis and treatment response of LGG patients. Consensus clustering, k-means clustering and Nonnegative Matrix Factorization was used for the TCGA-LGG dataset and identified two NETs-related subgroups. The prognostic hallmark and nomogram for LGG were developed, which consist of five differentially expressed NETRGs (FPR1, PTAFR, SLC11A1, ICAM1, LTF) based on nine analytic approaches. The ROC curves and calibration curves of our NETRGs signature and nomogram exhibited strong and robust prognosis prediction abilities in both the TCGA-LGG training set and CGGA-325, CGGA-693 validation sets. The prognosis for LGG individuals in the low-risk category was better. The TISCH was used to examine the five NETRGs at the single-cell level. Common immunological checkpoints were expressed at greater levels in high-risk individuals. LGG individuals in the low-risk category posses a higher likelihood of being sensitive to Carmustine and Vincristine, as indicated by the drug sensitivity analysis. The qRT-PCR experiment and immunohistochemistry images confirmed that the expression of FPR1, PTAFR, SLC11A1 and ICAM1 are higher in low-grade oligodendroglioma. The NETRGs signature and nomogram can accurately and conveniently predict the LGG patients' prognosis, which can facilitate individualized treatment and the improvement of prognosis.

The maternal-fetal interface at single-cell resolution: uncovering the cellular anatomy of the placenta and decidua

The maternal-fetal interface represents a critical site of immunological interactions that can greatly influence pregnancy outcomes. The unique cellular composition and cell-cell interactions taking place within these tissues has spurred substantial research efforts focused on the maternal-fetal interface. With the recent advent of single-cell technologies, multiple investigators have applied such methods to gain an unprecedented level of insight into maternal-fetal communication. Here, we provide an overview of the dynamic cellular composition and cell-cell communications at the maternal-fetal interface as reported by single-cell investigations. By primarily focusing on data from pregnancies in the second and third trimesters, we aim to showcase how single-cell technologies have bolstered the foundational understanding of each cell's contribution to physiologic gestation. Indeed, single-cell technologies have enabled the examination of classical placental cells, such as the trophoblast, as well as uncovered new roles for structural cells now recognized as active participants in pregnancy and parturition, such as decidual and fetal stromal cells, which are reviewed herein. Furthermore, single-cell data investigating the ontogeny, function, differentiation, and interactions among immune cells present at the maternal-fetal interface, namely macrophages, T cells, dendritic cells, neutrophils, mast cells, innate lymphoid cells, natural killer cells, and B cells are discussed in this review. Moreover, a key output of single-cell investigations is the inference of cell-cell interactions, which has been leveraged to not only dissect the intercellular communications within specific tissues but also between compartments such as the decidua basalis and placental villi. Collectively, this review emphasizes the ways by which single-cell technologies have expanded the understanding of cell composition and cellular processes underlying pregnancy in mid-to-late gestation at the maternal-fetal interface, which can prompt their continued application to reveal new pathways and targets for the treatment of obstetrical disease.

CD121b-positive neutrophils predict immunosuppression in septic shock

Background

Septic shock is linked with high mortality and significant long-term morbidity in survivors. However, the specific role of neutrophils in septic shock pathophysiology remains scarce in recent research.

Methods

Peripheral blood immune cells from healthy donors and patients with septic shock were analyzed using single-cell RNA sequencing and batch RNA sequencing. We measured serum CD121b in both patients and healthy donors. Peripheral immune cells were isolated and exposed to either a CD121b recombinant protein or a CD121b blocking antibody to evaluate the expression of inflammatory factors. Additionally, in a humanized mouse sepsis model, the expression of CD121b in neutrophils across different tissues was assessed following treatment with all-trans retinoic acid (ATRA).

Results

This study identified a subset of CD10-CD121b+ neutrophils in the peripheral blood of patients with septic shock. These patients exhibited elevated concentrations of soluble CD121b in serum and urine. Furthermore, outcomes revealed that the presence of CD121b+ neutrophils positively correlated with the severity of septic shock. These cells displayed immunosuppressive characteristics; after blocking CD121b, proinflammatory cytokines increased in peripheral immune cells. Additionally, we found that treatment with ATRA down-regulated the expression of CD121b.

Conclusions

CD121b is closely associated with the progression of septic shock and may serve as a potential predictor indicator of immunosuppression for the condition.

Helminth infection favors reprogramming and proliferation of lung neutrophils

Neutrophils are a granulocytic population of myeloid cells that have critical effector functions during infectious disease but are generally thought to be short-lived and nonproliferative with markedly limited activation states. In these studies, we directly compared lung neutrophil activation following infection with different groups of pathogens including bacteria, fungi, and helminths. Our results demonstrate considerable heterogeneity depending on the type of infectious agent. In contrast to bacterial and fungal infection, after helminth infection neutrophils expressed markers associated with characteristic type 2 responses and unexpectedly upregulated genes associated with cell cycling and protein synthesis. Further studies showed reduced neutrophil cell death following helminth infection and increased proliferation, which was dependent on IL-4R signaling. This distinct subset of proliferating neutrophils expanded following helminth infection and was released from the endothelial niche to colocalize with invading parasites in the airways. These studies demonstrate a novel long-lived cycling phenotype for neutrophils following helminth infection.

Photoreceptor loss does not recruit neutrophils despite strong microglial activation

In response to central nervous system (CNS) injury, tissue resident immune cells such as microglia and circulating systemic neutrophils are often first responders. The degree to which these cells interact in response to CNS damage is poorly understood, and even less so, in the neural retina which poses a challenge for high resolution imaging in vivo. In this study, we deploy fluorescence adaptive optics scanning light ophthalmoscopy (AOSLO) to study fluorescent microglia and neutrophils in mice. We simultaneously track immune cell dynamics using label-free phase-contrast AOSLO at micron-level resolution. Retinal lesions were induced with 488 nm light focused onto photoreceptor (PR) outer segments. These lesions focally ablated PRs, with minimal collateral damage to cells above and below the plane of focus. We used in vivo (AOSLO, SLO and OCT) imaging to reveal the natural history of the microglial and neutrophil response from minutes-to-months after injury. While microglia showed dynamic and progressive immune response with cells migrating into the injury locus within 1-day after injury, neutrophils were not recruited despite close proximity to vessels carrying neutrophils only microns away. Post-mortem confocal microscopy confirmed in vivo findings. This work illustrates that microglial activation does not recruit neutrophils in response to acute, focal loss of PRs, a condition encountered in many retinal diseases.

Gasdermin D-dependent neutrophil extracellular traps exacerbate cytokine storm contributing to pyoderma gangrenosum pathogenesis

Pyoderma gangrenosum (PG) is characterized by the agonizing necrotizing ulcers with non-infectious neutrophil infiltration. Neutrophil extracellular traps (NETs) represent one of the mechanisms of neutrophils activation, and gasdermin D (GSDMD) plays a regulatory role in NETs. In this study, we discovered that the serum levels of NETs were elevated in PG patients compared to healthy controls. Injection of serum from PG patients into the dorsal skin of wild-type mice led to the formation of localized cutaneous ulcers. Furthermore, subsequent modeling demonstrated a significant increase of NETs and GSDMD in skin lesions and peripheral blood serum of wild-type mice. In GSDMD -/- mice, the severity of skin ulcers after modeling was significantly diminished. Overall, our findings shed light on the role of GSDMD in regulating the production of NETs by neutrophils and the release of inflammatory factors in the pathogenesis of PG and establish an animal model for studying PG.

Neutrophils negatively control IL-17A-producing γδ T cell frequencies in a contact-dependent manner under physiological conditions

Background

In addition to serving as the primary effector cells against infections, neutrophils have been implicated in the regulation of both innate and adaptive immunity. In this study, we aimed to investigate the role of neutrophils in the regulation of the immune system under physiological conditions.

Methods

The in vivo effect of neutrophils on the immune system was examined using neutropenic mice. The interaction between neutrophils and γδ T cells was investigated using an in vitro co-culture system.

Findings

Unexpectedly, we observed an accumulation of γδ T cells in the cervical lymph nodes of neutropenic mice. Transcriptomic analysis revealed that these γδ T cells exhibited unique expression profiles of cell surface molecules and genes involved in defense responses. Further characterization indicated that the accumulated γδ T cells were IL-17 producing CD44+CD62L-CD27- memory cells. Additionally, in vitro experiments demonstrated that neutrophils could inhibit the function of IL-17A producing γδ T cells by inducing cell death in a contact-dependent manner.

Conclusion

This present study demonstrates that neutrophils negatively regulate IL-17 producing γδ T cells under physiological conditions. Given that IL-17A is a critical cytokine for the recruitment of neutrophils to peripheral tissues, our study suggests that the crosstalk between neutrophils and IL-17A producing γδ T cells is a crucial mechanism for maintaining immune homeostasis under physiological conditions.

Neutrophil-derived vesicles control complement activation to facilitate inflammation resolution

Although subsets with immunosuppressive properties exist, neutrophils are typically known for their pro-inflammatory role and pathogen clearance capabilities. Here, we reveal that neutrophils can paradoxically aid in resolving inflammation by actively producing anti-inflammatory extracellular vesicles. These large aging-neutrophil-derived vesicles (LAND-Vs) do not fit into classical vesicle categorizations due to their specific size, structure, or biogenesis pathway. They are protected from efferocytotic clearance by phagocytes due to surface "do not eat me" signals and accumulate in the resolution phase of inflammation. CD55 on LAND-Vs exerts a robust, sustained anti-inflammatory effect by inhibiting complement 3 convertase, thereby reducing neutrophil recruitment and tissue damage. CD55+ LAND-Vs originate in ordered lipid raft domains, where CD55 accumulates asymmetrically during neutrophil aging, and are subsequently formed through RhoA-dependent budding. Collectively, LAND-V emerges as a pivotal physiological immunomodulator and showcases functions that transcend the limited lifespan of neutrophils, offering a therapeutic target for inflammatory and infectious diseases.

AMPK and CAMKK activation participate in early events of Toxoplasma gondii-triggered NET formation in bovine polymorphonuclear neutrophils

Toxoplasma gondii is an obligate intracellular apicomplexan parasite that infects humans, eventually causing severe diseases like prenatal or ocular toxoplasmosis. T. gondii also infects cattle but rarely induces clinical signs in this intermediate host type. So far, the innate immune mechanisms behind the potential resistance of bovines to clinical T. gondii infections remain unclear. Here, we present evidence on sustained activation of bovine polymorphonuclear neutrophils PMN by T. gondii tachyzoites, which is linked to a rise in cytoplasmic calcium concentrations, an enhancement of calcium/calmodulin-dependent protein kinase kinase 2 (CAMKK) and AMP-activated protein kinase (AMPK). NETosis is a specific form of programmed cell death, characterized by the release chromatin from the nucleus to the extracellular space resulting in formation of neutrophil extracellular traps (NETs). NETs can kill and entrap pathogens. In our experiments, NETosis was triggered by T. gondii, and this effector mechanism was enhanced by pre-treatments with the AMPK activator AICAR. Moreover, tachyzoite-mediated bovine neutrophil DNA release depended on MAPK- and store operated calcium entry- (SOCE) pathways since it was diminished by the inhibitors UO126 and 2-APB, respectively. Overall, we here provide new insights into early polymorphonuclear neutrophils responses against T. gondii for the bovine system.

Pemphigoid disease model systems for clinical translation

Pemphigoid diseases constitute a group of organ-specific autoimmune diseases characterized and caused by autoantibodies targeting autoantigens expressed in the skin and mucous membranes. Current therapeutic options are still based on unspecific immunosuppression that is associated with severe adverse events. Biologics, targeting the IL4-pathway or IgE are expected to change the treatment landscape of pemphigoid diseases. However, clinical studies demonstrated that targeting these pathways alone is most likely not sufficient to meet patient and healthcare partitioners expectations. Hence, model systems are needed to identify and validate novel therapeutic targets in pemphigoid diseases. These include pre-clinical animal models, in vitro and ex vivo model systems, hypothesis-driven drug repurposing, as well as exploitation of real-world-data. In this review, we will highlight the medical need for pemphigoid diseases, and in-depth discuss the advantages and disadvantages of the available pemphigoid disease model systems. Ultimately, we discuss how rapid translation can be achieved for the benefit of the patients.

Toxoplasma induced cytokine release syndrome is critically dependent on the expression of pore-forming Perforin-Like Protein-1

Acute virulence in Toxoplasma gondii is linked to an excessive proinflammatory cytokine cascade during laboratory murine infection. Previous work showed that T. gondii secretes a pore forming protein, PLP1, that is required for efficient cytolytic egress from host cells. Deletion of the PLP1 gene results in defective egress from infected culture cells and a marked reduction in parasite virulence. The goal of the present study was to gain insight into the nature of the attenuated virulence observed in PLP1 knockout compared to wild type (WT) RH parasites. Using in vivo bioluminescence imaging, we show that parasites lacking PLP1 establish an acute infection and disseminate throughout the infected mice. Histological tissue analysis indicates that parasites cause severe pathology, even in the absence of PLP1. However, mice infected with Δplp1 parasites evoke a protective inflammatory response, demonstrated by mouse survival and control of infection. Flow cytometric analysis was used to determine cellular changes occurring during both WT and Δplp1 parasite infection. Parasite control in the Δplp1 infection was associated with earlier activation of myeloid cells and a moderate neutrophil response that, by comparison, becomes the dominant infiltrating cell type of WT infection. Positive disease outcome during Δplp1 parasite infection is also associated with regulated induction of proinflammatory cytokines, including IFN-γ and TNF-α, and an earlier IL-10 regulatory response that is dysregulated during WT infection. Together these findings suggest a key role for Toxoplasma PLP1 in promoting a lethal inflammatory immune response during acute infection with a virulent strain of the parasite.

Investigating pulmonary neutrophil responses to inflammation in mice via flow cytometry

Neutrophils play a crucial role in maintaining lung health by defending against infections and participating in inflammation processes. Here we describe a detailed protocol for evaluating pulmonary neutrophil phenotype using a murine model of sterile inflammation induced by the fungal cell wall particle zymosan. We provide step-by-step instructions for the isolation of single cells from both lung tissues and airspaces, followed by comprehensive staining techniques for both cell surface markers and intracellular components. This protocol facilitates the sorting and detailed characterization of lung neutrophils via flow cytometry, making it suitable for downstream applications such as mRNA extraction, single-cell sequencing, and analysis of neutrophil heterogeneity. We also identify and discuss essential considerations for conducting successful neutrophil flow cytometry experiments. This work is aimed at researchers exploring the intricate functions of neutrophils in the lung under physiological and pathological conditions with the aid of flow cytometry.

New insights on extramedullary granulopoiesis and neutrophil heterogeneity in the spleen and its importance in disease

Neutrophils are traditionally viewed as uncomplicated exterminators that arrive quickly at sites of infection, kill pathogens, and then expire. However, recent studies employing modern transcriptomics coupled with novel imaging modalities have discovered that neutrophils exhibit significant heterogeneity within organs and have complex functional roles ranging from tissue homeostasis to cancer and chronic pathologies. This has revised the view that neutrophils are simplistic butchers, and there has been a resurgent interest in neutrophils. The spleen was described as a granulopoietic organ more than 4 decades ago, and studies indicate that neutrophils are briefly retained in the spleen before returning to circulation after proliferation. Transcriptomic studies have discovered that splenic neutrophils are heterogeneous and distinct compared with those in blood. This suggests that a unique hematopoietic niche exists in the splenic microenvironment, i.e., capable of programming neutrophils in the spleen. During severe systemic inflammation with an increased need of neutrophils, the spleen can adapt by producing neutrophils through emergency granulopoiesis. In this review, we describe the structure and microanatomy of the spleen and examine how cells within the splenic microenvironment help to regulate splenic granulopoiesis. A focus is placed on exploring the increase in splenic granulopoiesis to meet host needs during infection and inflammation. Emerging technologies such as single-cell RNA sequencing, which provide valuable insight into splenic neutrophil development and heterogeneity, are also discussed. Finally, we examine how tumors subvert this natural pathway in the spleen to generate granulocytic suppressor cells to promote tumor growth.

Neutrophil recruitment during intestinal inflammation primes Salmonella elimination by commensal E. coli in a context-dependent manner

Foodborne bacterial diarrhea involves complex pathogen-microbiota-host interactions. Pathogen-displacing probiotics are increasingly popular, but heterogeneous patient outcomes highlighted the need to understand individualized host-probiotic activity. Using the mouse gut commensal Escherichia coli 8178 and the human probiotic E. coli Nissle 1917, we found that the degree of protection against the enteric pathogen Salmonella enterica serovar Typhimurium (S. Tm) varies across mice with distinct gut microbiotas. Pathogen clearance is linked to enteropathy severity and subsequent recruitment of intraluminal neutrophils, which differs in a microbiota-dependent manner. By combining mouse knockout and antibody-mediated depletion models with bacterial genetics, we show that neutrophils and host-derived reactive oxygen species directly influence E. coli-mediated S. Tm displacement by potentiating siderophore-bound toxin killing. Our work demonstrates how host immune factors shape pathogen-displacing probiotic efficiency while also revealing an unconventional antagonistic interaction where a gut commensal and the host synergize to displace an enteric pathogen.

Neutrophil Heterogeneity in Wound Healing

Neutrophils are the most abundant type of immune cells and also the most underestimated cell defenders in the human body. In fact, their lifespan has also been extensively revised in recent years, going from a half-life of 8-10 h to a longer lifespan of up to 5.4 days in humans; it has been discovered that their mechanisms of defense are multiple and finely modulated, and it has been suggested that the heterogeneity of neutrophils occurs as well as in other immune cells. Neutrophils also play a critical role in the wound healing process, and their involvement is not limited to the initial stages of defense against pathogens, but extends to the inflammatory phase of tissue reconstruction. Neutrophil heterogeneity has recently been reported at the presence of distinct subtypes expressing different functional states, which contribute uniquely to the different phases of innate immunity and wound healing. This heterogeneity can be induced by the local microenvironment, by the presence of specific cytokines and by the type of injury. The different functional states of neutrophils enable a finely tuned response to injury and stress, which is essential for effective healing. Understanding the functional heterogeneity of neutrophils in wound healing can unveil potential pathological profiles and therapeutic targets. Moreover, the understanding of neutrophil heterogeneity dynamics could help in designing strategies to manage excessive inflammation or impaired healing processes. This review highlights the complexity of neutrophil heterogeneity and its critical roles throughout the phases of wound healing.