Multicenter Systems Analysis of Human Blood Reveals Immature Neutrophils in Males and During Pregnancy

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.

Soluble CD13 is a potential mediator of neutrophil-induced thrombogenic inflammation in SARS-CoV-2 infection

The soluble variant of the ectopeptidase CD13 (sCD13), released from the cell surface by matrix metalloproteinase 14 (MMP14), is a potent pro-inflammatory mediator, displaying chemotactic, angiogenic, and arthritogenic properties through bradykinin receptor B1 (B1R). We revealed a link between sCD13 and amplified neutrophil-mediated inflammatory responses in SARS-CoV-2 infection. sCD13 was markedly elevated in patients with COVID-19 and correlated with disease severity and variants, ethnicity, inflammation markers, and neutrophil extracellular trap formation (NETosis). Neutrophils treated with sCD13 showed heightened NETosis and chemotaxis, which were inhibited by sCD13 receptor blockade. Meanwhile sCD13 did not induce platelet aggregation. Single-cell analysis of COVID-19 lungs revealed coexpression of CD13 and MMP14 by various cell types, and higher CD13 expression compared with controls. Neutrophils with high CD13 mRNA were enriched for genes associated with immaturity, though CD13 protein expression was lower. Histological examination of COVID-19 lungs revealed CD13-positive leukocytes trapped in vessels with fibrin thrombi. Flow cytometry verified the presence of B1R and a second sCD13 receptor, protease-activated receptor 4, on monocytes and neutrophils. These findings identify sCD13 as a potential instigator of COVID-19-associated NETosis, potentiating vascular stress and thromboembolic complications. The potent pro-inflammatory effects of sCD13 may contribute to severe COVID-19, suggesting that sCD13 and its receptors might be therapeutic targets.

Pregnancy is associated with a simultaneous but independent increase in circulating CD177pos and immature low-density granulocytes

The neutrophil marker CD177 (NB1, HNA-2a) is expressed by 0-100% of circulating neutrophils in any given donor, dividing neutrophils into 2 distinct subpopulations (CD177pos and CD177neg). High proportions of CD177pos blood neutrophils have been linked to both systemic infections and a range of inflammatory pathologies, but whether this is a cause or a consequence of disease is not known. Many conditions displaying elevated CD177pos neutrophil proportions are also accompanied by the presence of circulating low-density granulocytes. Accordingly, it is tempting to speculate that these 2 events are connected (i.e. that proportions of CD177pos neutrophils increase as a result of an enlarged pool of circulating low-density granulocytes). A temporary increase in CD177pos neutrophils, in combination with the presence of low-density granulocytes, has been reported during pregnancy. The present study aimed to investigate whether elevated proportions of CD177pos neutrophils in peripheral blood from pregnant women can be attributed to the presence of low-density granulocytes. We found that low-density granulocytes were indeed present in pregnancy and included both immature and activated mature neutrophils. The proportion of CD177pos low-density granulocytes increased over time during pregnancy and correlated with a simultaneous increase in immature cells. However, most immature neutrophils were CD177neg, meaning that increased release of immature cells cannot explain the increased proportions of the CD177pos subtype. Therefore, although low-density granulocytes and CD177pos neutrophils are expanded simultaneously during pregnancy, these events occur independently from each other.

Sex-dependent gastrointestinal colonization resistance to MRSA is microbiota and Th17 dependent

Gastrointestinal (GI) colonization by methicillin-resistant Staphylococcus aureus (MRSA) is associated with a high risk of transmission and invasive disease in vulnerable populations. The immune and microbial factors that permit GI colonization remain unknown. Male sex is correlated with enhanced Staphylococcus aureus nasal carriage, skin and soft tissue infections, and bacterial sepsis. Here, we established a mouse model of sexual dimorphism during GI colonization by MRSA. Our results show that in contrast to male mice that were susceptible to persistent colonization, female mice rapidly cleared MRSA from the GI tract following oral inoculation in a manner dependent on the gut microbiota. This colonization resistance displayed by female mice was mediated by an increase in IL-17A+ CD4+ T cells (Th17) and dependent on neutrophils. Ovariectomy of female mice increased MRSA burden, but gonadal female mice that have the Y chromosome retained enhanced Th17 responses and colonization resistance. Our study reveals a novel intersection between sex and gut microbiota underlying colonization resistance against a major widespread pathogen.

Impact of peptidylarginine deiminase 4 (PAD4) deficiency in a fecal-induced peritonitis model of sepsis

BACKGROUND

Peptidylarginine deiminase 4 (PAD4) citrullinates histones, enabling the release of neutrophil extracellular traps. While neutrophil extracellular traps capture and kill pathogens, they also drive immunothrombosis, potentially worsening sepsis outcomes. However, it remains unclear whether PAD4 deficiency is beneficial or harmful in sepsis.

OBJECTIVES

To evaluate the impact of PAD4 deficiency in a fecal-induced peritonitis sepsis model, with and without antibiotic treatment, and incorporating fluid resuscitation in both sexes.

METHODS

Wild-type and PAD4 knockout (PAD4-/-) C57Bl/6 mice received intraperitoneal injections of fecal slurry (0.6 mg/g). Mice received buprenorphine every 8 hours and antibiotics/fluids every 12 hours. Survival studies were also conducted without antibiotics at a reduced fecal dose (0.4 mg/g). Mice were culled at 8 hours or 48 hours after infection. Organs, blood, and peritoneal cavity fluid were collected. Plasma levels of interleukin (IL)-6, IL-10, cell-free DNA, and thrombin-antithrombin were quantified, as well as bacterial loads in blood and peritoneal cavity fluid. Organ histology/immunohistochemistry was performed.

RESULTS

Female PAD4-/- mice had worsened survival compared with female wild-type mice. Male mice exhibited worse survival than females in both strains. Antibiotics eliminated survival differences between strains and sexes. Septic PAD4-/- mice had reduced IL-10 in the early phase of sepsis, increased lung myeloperoxidase, and exacerbated lung injury compared with septic wild-type mice.

CONCLUSION

PAD4 deficiency in female mice worsened survival in the fecal-induced peritonitis sepsis model. In both strains, male mice exhibited worse survival compared with their female counterparts. PAD4 deficiency is associated with reduced IL-10, increased neutrophil infiltration, and exacerbated lung injury. Antibiotics eliminated survival differences between strains and sexes.

The single-cell immune profile throughout gestation and its potential value for identifying women at risk for spontaneous preterm birth

Precisely timed immune adaptations, observed in the maternal circulation, underpin the notion of an immune clock of human pregnancy that supports its successful progression and completion at delivery. This immune clock is divided into three immunological phases, with the first phase starting at the time of conception and implantation, shifting into the second phase that supports homeostasis and tolerance throughout pregnancy, and culminating in the last phase of labor and parturition. Disruptions of this immune clock are reported in pregnancy complications such as spontaneous preterm birth. However, our understanding of the immune clock preceding spontaneous preterm birth remains scattered. In this review, we describe the chronology of maternal immune cell adaptations during healthy pregnancies and highlight its disruption in spontaneous preterm birth. With a focus on single-cell cytometric, proteomic and transcriptomic approaches, we review recent studies of term and spontaneous preterm pregnancies and discuss the need for future prospective studies aimed at tracking pregnancies longitudinally on a multi-omic scale. Such studies will be critical in determining whether spontaneous preterm pregnancies progress at an accelerated pace or follow a preterm-intrinsic pattern when compared to those delivered at term.

Sex-dependent gastrointestinal colonization resistance to MRSA is microbiota and Th17 dependent

Gastrointestinal (GI) colonization by methicillin-resistant Staphylococcus aureus (MRSA) is associated with a high risk of transmission and invasive disease in vulnerable populations. The immune and microbial factors that permit GI colonization remain unknown. Male sex is correlated with enhanced Staphylococcus aureus nasal carriage, skin and soft tissue infections, and bacterial sepsis. Here, we established a mouse model of sexual dimorphism during GI colonization by MRSA. Our results show that in contrast to male mice that were susceptible to persistent colonization, female mice rapidly cleared MRSA from the GI tract following oral inoculation in a manner dependent on the gut microbiota. This colonization resistance displayed by female mice was mediated by an increase in IL-17A+ CD4+ T cells (Th17) and dependent on neutrophils. Ovariectomy of female mice increased MRSA burden, but gonadal female mice that have the Y chromosome retained enhanced Th17 responses and colonization resistance. Our study reveals a novel intersection between sex and gut microbiota underlying colonization resistance against a major widespread pathogen.

Adaptations of neutrophils in cancer

There is a renewed interest in neutrophil biology, largely instigated by their prominence in cancer. From an immunologist's perspective, a conceptual breakthrough is the realization that prototypical inflammatory, cytotoxic leukocytes can be tamed to promote the survival and growth of other cells. This has sparked interest in defining the biological principles and molecular mechanisms driving the adaptation of neutrophils to cancer. Yet, many questions remain: is this adaptation mediated by reprogramming mature neutrophils inside the tumoral mass, or rather by rewiring granulopoiesis in the bone marrow? Why, in some instances, are neutrophils beneficial and in others detrimental to cancer? How many different functional programs can be induced in neutrophils by tumors, and is this dependent on the type of tumor? This review summarizes what we know about these questions and discusses therapeutic strategies based on our incipient knowledge of how neutrophils adapt to cancer.

CITMIC: Comprehensive Estimation of Cell Infiltration in Tumor Microenvironment based on Individualized Intercellular Crosstalk

The tumor microenvironment (TME) cells interact with each other and play a pivotal role in tumor progression and treatment response. A comprehensive characterization of cell and intercellular crosstalk in the TME is essential for understanding tumor biology and developing effective therapies. However, current cell infiltration analysis methods only partially describe the TME's cellular landscape and overlook cell-cell crosstalk. Here, this approach, CITMIC, can infer the cell infiltration of TME by simultaneously measuring 86 different cell types, constructing an individualized cell-cell crosstalk network based on functional similarities between cells, and using only gene transcription data. This is a novel approach to estimating the relative cell infiltration levels, which are shown to be superior to the current methods. The TME cell-based features generated by analyzing melanoma data are effective in predicting prognosis and treatment response. Interestingly, these features are found to be particularly effective in assessing the prognosis of high-stage patients, and this method is applied to multiple high-stage adenocarcinomas, where more significant prognostic performance is also observed. In conclusion, CITMIC offers a more comprehensive description of TME cell composition by considering cell-cell crosstalk, providing an important reference for the discovery of predictive biomarkers and the development of new therapeutic strategies.

Neutrophils drive sexual dimorphism in experimental periodontitis

The motivating premise of this study is to improve the treatment of periodontal disease by elucidating sex-specific mechanisms of periodontal disease progression. Men and women experience inflammation in fundamentally different ways and understanding the sex-specific biology leading to inflammation and bone loss in the periodontium will inevitably improve patient outcomes. We therefore examined clinical and immunological differences in the progression of periodontal disease using the ligature-induced periodontitis model. Periodontitis was induced in male and female C57BL/6j mice by tying a 5-0 silk suture around the left maxillary second molar. The ligature was left on for 7 or 21 days at which point maxillae were characterized for bone loss by μCT or immune infiltrate by flow cytometry. Neutrophil depletion was accomplished through systemic administration of a Ly6G antibody. Conditions were compared using two-way ANOVA with Tukey's multiple comparison correction from n≥5 animals. Ligature-induced periodontitis led to alveolar bone loss at both 7 and 21 days in both female and male mice. Males and females had approximately the same amount of linear bone loss 7 days post-ligature placement, while male mice had significantly more linear bone loss by day 21. Male mice had significantly more immune cells in their maxillae 7 days post ligature placement compared to female mice. Both male and female mice showed a shift in immune populations towards neutrophils, with no significant difference between males and females. Neutrophil counts were significantly elevated in male mice on day 7 but not day 21, while female mice did not have any statistically significant changes in neutrophil counts. Neutrophil depletion using a Ly6G antibody limited bone loss in male but not female mice relative to isotype antibody-treated controls. Analysis of single-cell sequencing data from human patients with periodontitis showed differences in neutrophil phenotypes that were also observed in a mouse model of periodontitis. Together, these data suggest a mechanistic role for neutrophil inflammation in sexual dimorphism in periodontitis.

Function of immune cells and effector molecules of the innate immune system in the establishment and maintenance of pregnancy in mammals - A review

In mammalian species, pregnancy is a complex process that involves the maternal recognition of pregnancy, implantation, decidualization, placentation, and parturition. The innate immune system is composed of cellular components, such as natural killer cells, neutrophils, monocytes, and macrophages, and effector molecules, such as cytokines, interferons, antimicrobial peptides, and complement components. The innate immune system plays a critical role as the first line of defense against infection or inflammation to maintain homeostasis and activate the adaptive immunity. During pregnancy, innate immune cells and effector molecules act on the regulation of innate immunity for host defense and processes such as embryo development, implantation, and placentation at the maternal-conceptus interface. In this review, we describe the components of the innate immune system and their functions at the maternal-conceptus interface to establish and maintain pregnancy in animal species that form hemochorial- or epitheliochorial-type placentas, including humans, rodents, ruminants, and pigs.

Bipotential B-neutrophil progenitors are present in human and mouse bone marrow and emerge in the periphery upon stress hematopoiesis

Hematopoiesis is a tightly regulated process that gets skewed toward myelopoiesis. This restrains lymphopoiesis, but the role of lymphocytes in this process is not well defined. To unravel the intricacies of neutrophil responses in COVID-19, we performed bulk RNAseq on neutrophils from healthy controls and COVID-19 patients. Principal component analysis revealed distinguishing neutrophil gene expression alterations in COVID-19 patients. ICU and ward patients displayed substantial transcriptional changes, with ICU patients exhibiting a more pronounced response. Intriguingly, neutrophils from COVID-19 patients, notably ICU patients, exhibited an enrichment of immunoglobulin (Ig) and B cell lineage-associated genes, suggesting potential lineage plasticity. We validated our RNAseq findings in a larger cohort. Moreover, by reanalyzing single-cell RNA sequencing (scRNAseq) data on human bone marrow (BM) granulocytes, we identified the cluster of granulocyte-monocyte progenitors (GMP) enriched with Ig and B cell lineage-associated genes. These cells with lineage plasticity may serve as a resource depending on the host's needs during severe systemic infection. This distinct B cell subset may play a pivotal role in promoting myelopoiesis in response to infection. The scRNAseq analysis of BM neutrophils in infected mice further supported our observations in humans. Finally, our studies using an animal model of acute infection implicate IL-7/GM-CSF in influencing neutrophil and B cell dynamics. Elevated GM-CSF and reduced IL-7 receptor expression in COVID-19 patients imply altered hematopoiesis favoring myeloid cells over B cells. Our findings provide novel insights into the relationship between the B-neutrophil lineages during severe infection, hinting at potential implications for disease pathogenesis.

IMPORTANCE

This study investigates the dynamics of hematopoiesis in COVID-19, focusing on neutrophil responses. Through RNA sequencing of neutrophils from healthy controls and COVID-19 patients, distinct gene expression alterations are identified, particularly in ICU patients. Notably, neutrophils from COVID-19 patients, especially in the ICU, exhibit enrichment of immunoglobulin and B cell lineage-associated genes, suggesting potential lineage plasticity. Validation in a larger patient cohort and single-cell analysis of bone marrow granulocytes support the presence of granulocyte-monocyte progenitors with B cell lineage-associated genes. The findings propose a link between B-neutrophil lineages during severe infection, implicating a potential role for these cells in altered hematopoiesis favoring myeloid cells over B cells. Elevated GM-CSF and reduced IL-7 receptor expression in stress hematopoiesis suggest cytokine involvement in these dynamics, providing novel insights into disease pathogenesis.

Prognostic Significance of Plasma Neutrophil Extracellular Trap Levels in Patients with Non-Small Cell Lung Cancer Treated with Immune Checkpoint Inhibitors

Neutrophil extracellular traps (NETs) released from neutrophils are related to cancer progression. However, the relationship between the therapeutic effects of immune checkpoint inhibitors (ICIs) such as anti-PD-1 and anti-PD-L1 antibodies and plasma NET concentration in patients with non-small cell lung cancer (NSCLC) is poorly understood. In this study, concentrations of citrullinated histone H3 (CitH3), a surrogate marker of NETs, in plasma before/after treatment were examined in patients with advanced or recurrent NSCLC undergoing ICI treatment (n = 185). The clinical significances of NET levels before/after treatment and posttreatment changes were statistically evaluated. As a result, multivariate Cox analysis showed that high NET levels before treatment were statistically significant predictors of unfavorable overall survival (OS; p < 0.001, HR 1.702, 95% CI 1.356-2.137) and progression-free survival (PFS; p < 0.001, HR 1.566, 95% CI 1.323-1.855). The Kaplan-Meier curves showed significant separation between the high- and low-NET groups in OS (p = 0.002) and PFS (p < 0.001). Additionally, high NET levels after treatment were also significantly associated with worse OS (p < 0.001) and PFS (p < 0.001) by multivariate Cox analysis. Notably, the pretreatment NET levels were significantly correlated with the plasma levels of NET-related inflammatory cytokines, such as IL-6 and IL-8, and with NET-related gene expression and immune-suppressive profile in peripheral blood mononuclear cells. Our findings suggest that NETs released from activated neutrophils might reduce the clinical efficacy of ICIs in patients with NSCLC.

Neutrophils, an emerging new therapeutic platform

Neutrophils possess unique characteristics that render them indispensable to health, and patients with irregular neutrophil counts or functions suffer from increased morbidity and mortality. As neutrophils are short-lived postmitotic cells, genetic aberrations cannot be corrected directly in neutrophils and must be targeted in their progenitors. Neutrophils are increasingly being contemplated for a range of therapeutic applications, including restoration or modulation of immune function and targeting of solid tumors. This review addresses the state-of-the-art in neutrophil transfusions and their possible applications for infectious disease prevention and treatment. It offers a landscape of the most recent gene therapy approaches to address neutrophil-related genetic diseases. We also discuss how ongoing research could broaden the applicability of neutrophil-based therapies to solid cancer treatments and beyond.

Neutrophils in Cancer immunotherapy: friends or foes?

Neutrophils play a Janus-faced role in the complex landscape of cancer pathogenesis and immunotherapy. As immune defense cells, neutrophils release toxic substances, including reactive oxygen species and matrix metalloproteinase 9, within the tumor microenvironment. They also modulate the expression of tumor necrosis factor-related apoptosis-inducing ligand and Fas ligand, augmenting their capacity to induce tumor cell apoptosis. Their involvement in antitumor immune regulation synergistically activates a network of immune cells, bolstering anticancer effects. Paradoxically, neutrophils can succumb to the influence of tumors, triggering signaling cascades such as JAK/STAT, which deactivate the immune system network, thereby promoting immune evasion by malignant cells. Additionally, neutrophil granular constituents, such as neutrophil elastase and vascular endothelial growth factor, intricately fuel tumor cell proliferation, metastasis, and angiogenesis. Understanding the mechanisms that guide neutrophils to collaborate with other immune cells for comprehensive tumor eradication is crucial to enhancing the efficacy of cancer therapeutics. In this review, we illuminate the underlying mechanisms governing neutrophil-mediated support or inhibition of tumor progression, with a particular focus on elucidating the internal and external factors that influence neutrophil polarization. We provide an overview of recent advances in clinical research regarding the involvement of neutrophils in cancer therapy. Moreover, the future prospects and limitations of neutrophil research are discussed, aiming to provide fresh insights for the development of innovative cancer treatment strategies targeting neutrophils.

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. Secretion of LTB 4 -containing exosomes is required for effective neutrophil infiltration during inflammation. In this study, we show that neutrophils release nuclear DNA in a non-lytic, rapid, and repetitive manner, via a mechanism distinct from suicidal NET release and cell death. The packaging of nuclear DNA occurs in the lumen of nuclear envelope (NE)-derived multivesicular bodies (MVBs) that harbor the LTB 4 synthesizing machinery and is mediated by the lamin B receptor (LBR) and chromatin decondensation. Disruption of secreted exosome-associated DNA (SEAD) in a model of sterile inflammation in mouse skin amplifies and prolongs the presence of neutrophils, impeding the onset of resolution. Together, these findings advance our understanding of neutrophil functions during inflammation and the physiological significance of NETs, with implications for novel treatments for inflammatory disorders.

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.

A data browsing application for accessing gene and module-level blood transcriptome profiles of healthy pregnant women from high- and low-resource settings

Transcriptome profiling data, generated via RNA sequencing, are commonly deposited in public repositories. However, these data may not be easily accessible or usable by many researchers. To enhance data reuse, we present well-annotated, partially analyzed data via a user-friendly web application. This project involved transcriptome profiling of blood samples from 15 healthy pregnant women in a low-resource setting, taken at 6 consecutive time points beginning from the first trimester. Additional blood transcriptome profiles were retrieved from the National Center for Biotechnology Information (NCBI) Gene Expression Omnibus (GEO) public repository, representing a cohort of healthy pregnant women from a high-resource setting. We analyzed these datasets using the fixed BloodGen3 module repertoire. We deployed a web application, accessible at https://thejacksonlaboratory.shinyapps.io/BloodGen3_Pregnancy/which displays the module-level analysis results from both original and public pregnancy blood transcriptome datasets. Users can create custom fingerprint grid and heatmap representations via various navigation options, useful for reports and manuscript preparation. The web application serves as a standalone resource for exploring blood transcript abundance changes during pregnancy. Alternatively, users can integrate it with similar applications developed for earlier publications to analyze transcript abundance changes of a given BloodGen3 signature across a range of disease cohorts. Database URL: https://thejacksonlaboratory.shinyapps.io/BloodGen3_Pregnancy/.

Breast Cancer Immunity: It is TIME for the Next Chapter

Our ability to interrogate the tumor immune microenvironment (TIME) at an ever-increasing granularity has uncovered critical determinants of disease progression. Not only do we now have a better understanding of the immune response in breast cancer, but it is becoming possible to leverage key mechanisms to effectively combat this disease. Almost every component of the immune system plays a role in enabling or inhibiting breast tumor growth. Building on early seminal work showing the involvement of T cells and macrophages in controlling breast cancer progression and metastasis, single-cell genomics and spatial proteomics approaches have recently expanded our view of the TIME. In this article, we provide a detailed description of the immune response against breast cancer and examine its heterogeneity in disease subtypes. We discuss preclinical models that enable dissecting the mechanisms responsible for tumor clearance or immune evasion and draw parallels and distinctions between human disease and murine counterparts. Last, as the cancer immunology field is moving toward the analysis of the TIME at the cellular and spatial levels, we highlight key studies that revealed previously unappreciated complexity in breast cancer using these technologies. Taken together, this article summarizes what is known in breast cancer immunology through the lens of translational research and identifies future directions to improve clinical outcomes.

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

BACKGROUND

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

SUMMARY

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

KEY MESSAGES

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

Neutrophil extracellular traps regulating tumorimmunity in hepatocellular carcinoma

As a component of the innate immune system, there is emerging evidence to suggest that neutrophils may play a critical role in the initiation and progression of hepatocellular carcinoma (HCC). Neutrophil extracellular traps (NETs) are web-like chromatin structures that protrude from the membranes during neutrophil activation. Recent research has shown that NETs, which are at the forefront of the renewed interest in neutrophil studies, are increasingly intertwined with HCC. By exploring the mechanisms of NETs in HCC, we aim to improve our understanding of the role of NETs and gain deeper insights into neutrophil biology. Therefore, this article provides a summary of key findings and discusses the emerging field of NETs in HCC.

Mitochondria-induced formation of neutrophil extracellular traps is enhanced in the elderly via Toll-like receptor 9

Neutrophil extracellular traps are potent antimicrobial weapons; however, their formation during sterile inflammation is detrimental, and the mechanism of induction is still unclear. Since advanced age is the primary clinical risk factor for poor outcomes in inflammatory diseases, we hypothesized that sterile stimuli, represented by mitochondria, would induce neutrophil extracellular trap formation in an age-dependent manner. Therefore, we analyzed induction of neutrophil extracellular traps in patients grouped according to age or immune status and observed that neutrophils from elderly patients responded to the presence of mitochondria with enhanced neutrophil extracellular trap formation. These neutrophil extracellular traps were also found to be more oxidized and exhibited higher resistance to DNase I degradation. Additionally, a higher concentration of residual neutrophil extracellular traps was detected in the plasma of the elderly. This plasma was capable of priming neutrophils through TLR9-mediated signaling, leading to further neutrophil extracellular trap formation, which was successfully inhibited with chloroquine. Finally, in a mouse model of mitochondria-induced acute lung injury, we observed that neutrophils from aged mice displayed impaired chemotactic activity but exhibited a trend of higher neutrophil extracellular trap formation. Thus, we propose that residual neutrophil extracellular traps circulating in the elderly preactivate neutrophils, making them more prone to enhanced neutrophil extracellular trap formation when exposed to mitochondria during sterile inflammation. Further investigation is needed to determine whether this vicious circle could be a suitable therapeutic target.

Advances in Clinical Mass Cytometry

The advent of high-dimensional single-cell technologies has enabled detection of cellular heterogeneity and functional diversity of immune cells during health and disease conditions. Because of its multiplexing capabilities and limited compensation requirements, mass cytometry or cytometry by time of flight (CyTOF) has played a superior role in immune monitoring compared with flow cytometry. Further, it has higher throughput and lower cost compared with other single-cell techniques. Several published articles have utilized CyTOF to identify cellular phenotypes and features associated with disease outcomes. This article introduces CyTOF-based assays to profile immune cell-types, cell-states, and their applications in clinical research.

Preoperative Immature Neutrophils Predict Clinical Outcomes in Patients with Uncomplicated Type-B Aortic Dissection After Thoracic Endovascular Aortic Repair

Purpose

Inflammation is a hallmark of the initial development and progression of aortic dissection. This study aimed to investigate the predictive value of preoperative neutrophils in aorta-related adverse events (AAEs) after thoracic endovascular aortic repair (TEVAR) for type B aortic dissection (TBAD).

Patients and Methods

A total of 80 patients with TBAD undergoing TEVAR were enrolled in our hospital. Preoperative inflammatory markers, including white blood cells (WBCs), neutrophils, neutrophil-to-lymphocyte ratio (NLR) and plasma high-sensitivity C-reactive protein (hs-CRP), were measured. Circulating neutrophil subpopulation was determined by flow cytometry. Kaplan-Meier curve was performed to determine whether neutrophil subsets independently predicted aorta-related adverse events (AAEs) after TEVAR.

Results

Compared with control group, the prevalence of hypertension and the levels of inflammatory indicators including WBCs, total neutrophils, NLR, immature neutrophils and hs-CRP were significantly higher in TBAD patients. Receiver operating characteristic (ROC) curve showed that NLR, absolute number of total neutrophils and percent CD10- immature neutrophils had excellent area under curves. During the 18-month follow-up, 16 (20.0%) were reported to occur AAEs, while 4 deaths (5.0%) were documented. Percent immature neutrophil was markedly higher in TBAD patients experiencing AAEs as compared with those without AAEs. Kaplan-Meier curve and Cox regression analysis demonstrated that percent immature neutrophil was the only predictor correlated with the occurrence of AAEs (hazard ratio 7.66, 95% CI: 2.91, 20.17, P = 0.018).

Conclusion

Increased CD10- immature neutrophils could act as a potential biomarker related to long-term adverse outcomes in TBAD patients following TEVAR.

Circulating and Tumor-Associated Neutrophils in the Era of Immune Checkpoint Inhibitors: Dynamics, Phenotypes, Metabolism, and Functions

Neutrophils are the most abundant myeloid cells in the blood and are a considerable immunological component of the tumor microenvironment. However, their functional importance has often been ignored, as they have always been considered a mono-dimensional population of terminally differentiated, short-living cells. During the last decade, the use of cutting-edge, single-cell technologies has revolutionized the classical view of these cells, unmasking their phenotypic and functional heterogeneity. In this review, we summarize the emerging concepts in the field of neutrophils in cancer, by reviewing the recent literature on the heterogeneity of both circulating neutrophils and tumor-associated neutrophils, as well as their possible significance in tumor prognosis and resistance to immune checkpoint inhibitors.

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.

Formalin-evoked pain triggers sex-specific behavior and spinal immune response

Mounting evidence shows sex-related differences in the experience of pain with women suffering more from chronic pain than men. Yet, our understanding of the biological basis underlying those differences remains incomplete. Using an adapted model of formalin-induced chemical/inflammatory pain, we report here that in contrast to male mice, females distinctly display two types of nocifensive responses to formalin, distinguishable by the duration of the interphase. Females in proestrus and in metestrus exhibited respectively a short-lasting and a long-lasting interphase, underscoring the influence of the estrus cycle on the duration of the interphase, rather than the transcriptional content of the dorsal horn of the spinal cord (DHSC). Additionally, deep RNA-sequencing of DHSC showed that formalin-evoked pain was accompanied by a male-preponderant enrichment in genes associated with the immune modulation of pain, revealing an unanticipated contribution of neutrophils. Taking advantage of the male-enriched transcript encoding the neutrophil associated protein Lipocalin 2 (Lcn2) and using flow cytometry, we confirmed that formalin triggered the recruitment of LCN2-expressing neutrophils in the pia mater of spinal meninges, preferentially in males. Our data consolidate the contribution of female estrus cycle to pain perception and provide evidence supporting a sex-specific immune regulation of formalin-evoked pain.

Sex differences in the inflammatory response to stroke

Ischemic stroke is a leading cause of morbidity and mortality and disproportionally affects women, in part due to their higher longevity. Older women have poorer outcomes after stroke with high rates of cognitive deficits, depression, and reduced quality of life. Post-stroke inflammatory responses are also sexually dimorphic and drive differences in infarct size and recovery. Factors that influence sex-specific immune responses can be both intrinsic and extrinsic. Differences in gonadal hormone exposure, sex chromosome compliment, and environmental/social factors can drive changes in transcriptional and metabolic profiles. In addition, how these variables interact, changes across the lifespan. After the onset of ischemic injury, necrosis and apoptosis occur, which activate microglia and other glial cells within the central nervous system, promoting the release of cytokines and chemokines and neuroinflammation. Cells involved in innate and adaptive immune responses also have dual functions after stroke as they can enhance inflammation acutely, but also contribute to suppression of the inflammatory cascade and later repair. In this review, we provide an overview of the current literature on sex-specific inflammatory responses to ischemic stroke. Understanding these differences is critical to identifying therapeutic options for both men and women.

Maternal Dietary Inflammatory Potential and Offspring Birth Outcomes in a Chinese Population

BACKGROUND

Chronic inflammation perturbations during pregnancy may impact fetal growth; however, research on the association between dietary inflammation and birth outcomes is limited and inconsistent.

OBJECTIVES

This study seeks to assess whether the dietary inflammatory potential is related to birth outcomes among pregnant women in China.

METHODS

A total of 7194 mothers aged 17-46 y and their infants in China were included in this cross-sectional study. Dietary intake was assessed by a FFQ, which yielded scores on the energy-adjusted dietary inflammatory index (E-DII). Birth outcomes included birth weight, gestational age, birth weight z score, low birth weight (LBW), macrosomia, preterm birth, small-for-gestational-age (SGA), large-for-gestational-age (LGA), and birth defects. Generalized estimating equation and restricted cubic spline fit each outcome on continuous or quartiles of E-DII after adjusting for covariates.

RESULTS

The maternal E-DII ranged from -5.35 to 6.77. Overall, birth weight and gestation age (mean ± SD) were 3267.9 ± 446.7 g and 39.6 ± 1.3 wk, respectively, and the birth weight z score was 0.02 ± 1.14. A total of 3.2% of infants were born with LBW, 6.1% with macrosomia, 3.0% were preterm birth, 10.7% were born SGA, 10.0% were born LGA, and 2.0% were born with birth defects. E-DII was associated with a 9.8 g decrease in birth weight (95% CI: -16.9, -2.6) and a 1.09-fold (95% CI: 1.01, 1.18), 1.11-fold (95% CI: 1.02, 1.21), and 1.12-fold (95% CI: 1.02, 1.24) greater risk of LBW, preterm birth, and birth defects, respectively. The maternal E-DII score was nonlinearly associated with gestational age (P for linearity = 0.009, P for curvature = 0.044).

CONCLUSIONS

Among pregnant Chinese women, proinflammatory diets during pregnancy were related to reduced offspring birth weight and an increased risk of LBW, preterm birth, and birth defects. These findings might inform potential prevention strategies for pregnant women in China.

Gender-Specific Impact of Sex Hormones on the Immune System

Sex hormones are key determinants of gender-related differences and regulate growth and development during puberty. They also exert a broad range modulation of immune cell functions, and a dichotomy exists in the immune response between the sexes. Both clinical and animal models have demonstrated that androgens, estrogens, and progestogens mediate many of the gender-specific differences in immune responses, from the susceptibility to infectious diseases to the prevalence of autoimmune disorders. Androgens and progestogens mainly promote immunosuppressive or immunomodulatory effects, whereas estrogens enhance humoral immunity both in men and in women. This study summarizes the available evidence regarding the physiological effects of sex hormones on human immune cell function and the underlying biological mechanisms, focusing on gender differences triggered by different amounts of androgens between males and females.

Sex differences in depression: An immunological perspective

Depression is a heterogenous disorder with symptoms that present differently across individuals. In a subset of people depression is associated with alterations of the immune system that may contribute to disorder onset and symptomology. Women are twice as likely to develop depression and on average have a more sensitive adaptive and innate immune system when compared to men. Sex differences in pattern recognition receptors (PRRs), release of damage-associated molecular patterns (DAMPs), cell populations, and circulating cytokines play a critical role in inflammation onset. Sex differences in innate and adaptive immunity change the response of and repair to damage caused by dangerous pathogens or molecules in the body. This article reviews the evidence for sex specific immune responses that contribute to the sex differences in symptoms of depression that may account for the higher rate of depression in women.

Immune-metabolic adaptations in pregnancy: A potential stepping-stone to sepsis

Physiological shifts during pregnancy predispose women to a higher risk of developing sepsis resulting from a maladapted host-response to infection. Insightful studies have delineated subtle point-changes to the immune system during pregnancy. Here, we present an overlay of these point-changes, asking what changes and when, at a physiological, cellular, and molecular systems-level in the context of sepsis. We identify distinct immune phases in pregnancy delineated by placental hormone-driven changes in homeostasis setpoints of the immune and metabolic systems that subtly mirrors changes observed in sepsis. We propose that pregnancy immune-metabolic setpoint changes impact feedback thresholds that increase risk for a maladapted host-response to infection and thus act as a stepping-stone to sepsis. Defining maternal immune-metabolic setpoint changes is not only vital for tailoring the right diagnostic tools for early management of maternal sepsis but will facilitate an unravelling of the pathophysiological pathways that predispose an individual to sepsis.

Gestationally dependent immune organization at the maternal-fetal interface

The immune system and placenta have a dynamic relationship across gestation to accommodate fetal growth and development. High-resolution characterization of this maternal-fetal interface is necessary to better understand the immunology of pregnancy and its complications. We developed a single-cell framework to simultaneously immuno-phenotype circulating, endovascular, and tissue-resident cells at the maternal-fetal interface throughout gestation, discriminating maternal and fetal contributions. Our data reveal distinct immune profiles across the endovascular and tissue compartments with tractable dynamics throughout gestation that respond to a systemic immune challenge in a gestationally dependent manner. We uncover a significant role for the innate immune system where phagocytes and neutrophils drive temporal organization of the placenta through remarkably diverse populations, including PD-L1⁺ subsets having compartmental and early gestational bias. Our approach and accompanying datasets provide a resource for additional investigations into gestational immunology and evoke a more significant role for the innate immune system in establishing the microenvironment of early pregnancy.

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.

Pregnancy imparts distinct systemic adaptive immune function

PROBLEM

Pregnancy represents a state of systemic immune activation that is primarily driven by alterations in circulating innate immune cells. Recent studies have suggested that cellular adaptive immune components, T cells and B cells, also undergo changes throughout gestation. However, the phenotypes and functions of such adaptive immune cells are poorly understood. Herein, we utilized high-dimensional flow cytometry and functional assays to characterize T-cell and B-cell responses in pregnant and non-pregnant women.

METHODS

Peripheral blood mononuclear cells from pregnant (n = 20) and non-pregnant (n = 25) women were used for phenotyping of T-cell and B-cell subsets. T-cell proliferation and B-cell activation were assessed by flow cytometry after in vitro stimulation, and lymphocyte cytotoxicity was evaluated by using a cell-based assay. Statistical comparisons were performed with linear mixed-effects models.

RESULTS

Pregnancy was associated with modestly enhanced basal activation of peripheral CD4+ T cells. Both CD4+ and CD8+ T cells from pregnant women showed increased activation-induced proliferation; yet, a reduced proportion of these cells expressed activation markers compared to non-pregnant women. There were no differences in peripheral lymphocyte cytotoxicity between study groups. A greater proportion of B cells from pregnant women displayed memory-like and activated phenotypes, and such cells exhibited higher activation following stimulation.

CONCLUSION

Maternal circulating T cells and B cells display distinct responses during pregnancy. The former may reflect the unique capacity of T cells to respond to potential threats without undergoing aberrant activation, thereby preventing systemic inflammatory responses that can lead to adverse perinatal consequences.

Neutrophil extracellular traps: from physiology to pathology

At the frontline of the host defence response, neutrophil antimicrobial functions have adapted to combat infections and injuries of different origins and magnitude. The release of web-like DNA structures named neutrophil extracellular traps (NETs) constitutes an important mechanism by which neutrophils prevent pathogen dissemination or deal with microorganisms of a bigger size. At the same time, nuclear and granule proteins with microbicidal activity bind to these DNA structures promoting the elimination of entrapped pathogens. However, these toxic properties may produce unwanted effects in the host, when neutrophils uncontrollably release NETs upon persistent inflammation. As a consequence, NET accumulation can produce vessel occlusion, tissue damage, and prolonged inflammation associated with the progression and exacerbation of multiple pathologic conditions. This review outlines recent advances in understanding the mechanisms of NET release and functions in sterile disease. We also discuss mechanisms of physiological regulation and the importance of neutrophil heterogeneity in NET formation and composition.

Neutrophil extracellular traps in systemic autoimmune and autoinflammatory diseases

Systemic autoimmune diseases are characterized by the failure of the immune system to differentiate self from non-self. These conditions are associated with significant morbidity and mortality, and they can affect many organs and systems, having significant clinical heterogeneity. Recent discoveries have highlighted that neutrophils, and in particular the neutrophil extracellular traps that they can release upon activation, can have central roles in the initiation and perpetuation of systemic autoimmune disorders and orchestrate complex inflammatory responses that lead to organ damage. Dysregulation of neutrophil cell death can lead to the modification of autoantigens and their presentation to the adaptive immune system. Furthermore, subsets of neutrophils that seem to be more prevalent in patients with systemic autoimmune disorders can promote vascular damage and increased oxidative stress. With the emergence of new technologies allowing for improved assessments of neutrophils, the complexity of neutrophil biology and its dysregulation is now starting to be understood. In this Review, we provide an overview of the roles of neutrophils in systemic autoimmune and autoinflammatory diseases and address putative therapeutic targets that may be explored based on this new knowledge.

Sexual dimorphism in immune cell responses following stroke

Recent bodies of work in regard to stroke have revealed significant sex differences in terms of risk and outcome. While differences in sex hormones have been the focus of earlier research, the reasons for these differences are much more complex and require further identification. This review covers differences in sex related immune responses with a focus on differences in immune cell composition and function. While females are more susceptible to immune related diseases, they seem to have better outcomes from stroke at the experimental level with reduced pro-inflammatory responses. However, at the clinical level, the picture is much more complex with worse neurological outcomes from stroke. While the use of exogenous sex steroids can replicate some of these findings, it is apparent that many other factors are involved in the modulation of immune responses. As a result, more research is needed to better understand these differences and identify appropriate interventions and risk modification.

Establishment of Review Criteria Coordinating With the Automated Digital Cell Morphology Identification System in a Specialized Women’s and Children’s Hospital

Objective

We aimed to establish appropriate review criteria for blood cell analysis in a specialized women’s and children’s hospital. Also, the CellaVision DI-60, was developed as one of the automated digital cell morphology analyzer, we evaluated if it was shown to be most effective under the certain review criteria.

Methods

A total of 2890 blood samples were detected to optimize the previously established review criteria for women and children with the Sysmex XE-2100. A total of 623 samples were used to validate the criteria.

Results

The microscopic-review rate based on the initial review criteria was 51.0%. After optimization, it was reduced to 17.3% and the false-negative rate was 3.85%. There was &gt; 80% consistency between manual review results and CellaVision DI-60 preclassification when samples triggered the platelet- or red cell-related rules. The sensitivity for abnormalities (immature granulocytes, nucleated red blood cells) of reclassification was 90% to 100% and the false-negative rate was &lt; 5%. However, direct microscopic review was required when the “Blasts/AbnLympho?” and “Atypical Lympho?” flags were triggered.

Conclusion

Specialized review criteria are needed for women and children. An automated morphology identification system might help to improve the review criteria.

Development of a standardized and validated flow cytometry approach for monitoring of innate myeloid immune cells in human blood

Innate myeloid cell (IMC) populations form an essential part of innate immunity. Flow cytometric (FCM) monitoring of IMCs in peripheral blood (PB) has great clinical potential for disease monitoring due to their role in maintenance of tissue homeostasis and ability to sense micro-environmental changes, such as inflammatory processes and tissue damage. However, the lack of standardized and validated approaches has hampered broad clinical implementation. For accurate identification and separation of IMC populations, 62 antibodies against 44 different proteins were evaluated. In multiple rounds of EuroFlow-based design-testing-evaluation-redesign, finally 16 antibodies were selected for their non-redundancy and separation power. Accordingly, two antibody combinations were designed for fast, sensitive, and reproducible FCM monitoring of IMC populations in PB in clinical settings (11-color; 13 antibodies) and translational research (14-color; 16 antibodies). Performance of pre-analytical and analytical variables among different instruments, together with optimized post-analytical data analysis and reference values were assessed. Overall, 265 blood samples were used for design and validation of the antibody combinations and in vitro functional assays, as well as for assessing the impact of sample preparation procedures and conditions. The two (11- and 14-color) antibody combinations allowed for robust and sensitive detection of 19 and 23 IMC populations, respectively. Highly reproducible identification and enumeration of IMC populations was achieved, independently of anticoagulant, type of FCM instrument and center, particularly when database/software-guided automated (vs. manual “expert-based”) gating was used. Whereas no significant changes were observed in identification of IMC populations for up to 24h delayed sample processing, a significant impact was observed in their absolute counts after &gt;12h delay. Therefore, accurate identification and quantitation of IMC populations requires sample processing on the same day. Significantly different counts were observed in PB for multiple IMC populations according to age and sex. Consequently, PB samples from 116 healthy donors (8-69 years) were used for collecting age and sex related reference values for all IMC populations. In summary, the two antibody combinations and FCM approach allow for rapid, standardized, automated and reproducible identification of 19 and 23 IMC populations in PB, suited for monitoring of innate immune responses in clinical and translational research settings.

Pathological mechanisms and crosstalk among different forms of cell death in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a systemic autoimmune disorder characterized by a profound immune dysregulation and the presence of a variety of autoantibodies. Aberrant activation of programmed cell death (PCD) signaling and accelerated cell death is critical in the immunopathogenesis of SLE. Accumulating cellular components from the dead cells and ineffective clearance of the dead cell debris, in particular the nucleic acids and nucleic acids-protein complexes, provide a stable source of self-antigens, which potently activate auto-reactive B cells and promote IFN-I responses in SLE. Different cell types display distinct susceptibility and characteristics to a certain type of cell death, while different PCDs in various cells have mutual and intricate connections to promote immune dysregulation and contribute to the development of SLE. In this review, we discuss the role of various cell death pathways and their interactions in the pathogenesis of SLE. An in depth understanding of the interconnections among various forms cell death in SLE will lead to a better understanding of disease pathogenesis, shedding light on the development of novel therapeutic targets.

Sex Steroids Effects on Asthma: A Network Perspective of Immune and Airway Cells

A multitude of evidence has suggested the differential incidence, prevalence and severity of asthma between males and females. A compilation of recent literature recognized sex differences as a significant non-modifiable risk factor in asthma pathogenesis. Understanding the cellular and mechanistic basis of sex differences remains complex and the pivotal point of this ever elusive quest, which remains to be clarified in the current scenario. Sex steroids are an integral part of human development and evolution while also playing a critical role in the conditioning of the immune system and thereby influencing the function of peripheral organs. Classical perspectives suggest a pre-defined effect of sex steroids, generalizing estrogens popularly under the “estrogen paradox” due to conflicting reports associating estrogen with a pro- and anti-inflammatory role. On the other hand, androgens are classified as “anti-inflammatory,” serving a protective role in mitigating inflammation. Although considered mainstream and simplistic, this observation remains valid for numerous reasons, as elaborated in the current review. Women appear immune-favored with stronger and more responsive immune elements than men. However, the remarkable female predominance of diverse autoimmune and allergic diseases contradicts this observation suggesting that hormonal differences between the sexes might modulate the normal and dysfunctional regulation of the immune system. This review illustrates the potential relationship between key elements of the immune cell system and their interplay with sex steroids, relevant to structural cells in the pathophysiology of asthma and many other lung diseases. Here, we discuss established and emerging paradigms in the clarification of observed sex differences in asthma in the context of the immune system, which will deepen our understanding of asthma etiopathology.

Neutrophil phenotypes and functions in cancer: A consensus statement

Neutrophils are the first responders to infection and inflammation and are thus a critical component of innate immune defense. Understanding the behavior of neutrophils as they act within various inflammatory contexts has provided insights into their role in sterile and infectious diseases; however, the field of neutrophils in cancer is comparatively young. Here, we summarize key concepts and current knowledge gaps related to the diverse roles of neutrophils throughout cancer progression. We discuss sources of neutrophil heterogeneity in cancer and provide recommendations on nomenclature for neutrophil states that are distinct in maturation and activation. We address discrepancies in the literature that highlight a need for technical standards that ought to be considered between laboratories. Finally, we review emerging questions in neutrophil biology and innate immunity in cancer. Overall, we emphasize that neutrophils are a more diverse population than previously appreciated and that their role in cancer may present novel unexplored opportunities to treat cancer.

Single-cell atlas of peripheral blood mononuclear cells from pregnant women

Background

During pregnancy, mother–child interactions trigger a variety of subtle changes in the maternal body, which may be reflected in the status of peripheral blood mononuclear cells (PBMCs). Although these cells are easy to access and monitor, a PBMC atlas for pregnant women has not yet been constructed.

Methods

We applied single‐cell RNA sequencing (scRNA‐seq) to profile 198,356 PBMCs derived from 136 pregnant women (gestation weeks 6 to 40) and a control cohort. We also used scRNA‐seq data to establish a transcriptomic clock and thereby predicted the gestational age of normal pregnancy.

Results

We identified reconfiguration of the peripheral immune cell phenotype during pregnancy, including interferon‐stimulated gene upregulation, activation of RNA splicing‐related pathways and immune activity of cell subpopulations. We also developed a cell‐type‐specific model to predict gestational age of normal pregnancy.

Conclusions

We constructed a single‐cell atlas of PBMCs in pregnant women spanning the entire gestation period, which should help improve our understanding of PBMC composition turnover in pregnant women.

Dysbiosis of the Female Murine Gut Microbiome Exacerbates Neutrophil-Mediated Vascular Allograft Injury by Affecting Immunoregulation by Acetate

BACKGROUND

The gut microbiota affects immune responses that cause organ transplant rejection, but the mechanisms by which this occurs remain poorly understood.

METHODS

We have examined, in a murine model, how disruption of the gut microbiota with antibiotics early in life alters this microbial community later in life to affect immune responses that injure vascular allografts.

RESULTS

Analysis of 16S rRNA and whole genome sequencing of the gut microbiota demonstrated that early life disruption of this microbial community with antibiotics caused a reduction in taxa and enzymatic genes involved in the synthesis of acetate, an immunoregulatory metabolite in mice and humans. When allograft vascular injury was examined, early life disruption of the gut microbiota increased neutrophil accumulation and related medial injury of transplanted arteries. Normalizing the gut microbiota by co-housing and oral administration of acetate prevented neutrophil-mediated vascular allograft injury.

CONCLUSIONS

Dysbiosis of the gut microbiome that reduces its production of the immunoregulatory metabolite acetate exacerbates neutrophil-mediated allograft vascular injury.

Longitudinal study of 2 patients with cyclic thrombocytopenia, STAT3 and MPL mutations

Cyclic thrombocytopenia (CTP) is a rare disease of periodic platelet count oscillations. The pathogenesis of CTP remains elusive. To study the underlying pathophysiology and genetic and cellular associations with CTP, we applied systems biology approaches to 2 patients with stable platelet cycling and reciprocal thrombopoietin (TPO) cycling at multiple time points through 2 cycles. Blood transcriptome analysis revealed cycling of platelet-specific genes, which are in parallel with and precede platelet count oscillation, indicating that cyclical platelet production leads platelet count cycling in both patients. Additionally, neutrophil and erythrocyte-specific genes also showed fluctuations correlating with platelet count changes, consistent with TPO effects on hematopoietic progenitors. Moreover, we found novel genetic associations with CTP. One patient had a novel germline heterozygous loss-of-function (LOF) thrombopoietin receptor (MPL) c.1210G>A mutation, and both had pathogenic somatic gain-of-function (GOF) variants in signal transducer and activator of transcription 3 (STAT3). In addition, both patients had clonal T-cell populations that remained stable throughout platelet count cycles. These mutations and clonal T cells may potentially involve in the pathogenic baseline in these patients, rendering exaggerated persistent thrombopoiesis oscillations of their intrinsic rhythm upon homeostatic perturbations. This work provides new insights into the pathophysiology of CTP and possible therapies.

Evaluation of immature granulocyte parameters in myeloid neoplasms assayed by Sysmex XN hematology analyzer

Immature granulocytes (IGs) have significance for the diagnosis of myeloid neoplasms (MNs). The current study aims to use a hematology analyzer to evaluate the accuracy of IG parameters in MNs. Blood specimens from 388 patients with MN, 524 with non-hematological neoplasms (non-HNs), including 109 patients with inflammation and 68 undergoing G-CSF administration, and 500 healthy control subjects were analyzed. IG parameters was assayed by Sysmex XN-9000 (XN) and compared with manual assessments. A high level of agreement between IG% derived from XN and manual measurements for MN patients (r = 0.828, p < 0.0001) was revealed but only a moderate correlation for acute myeloid leukemia patients (AML; r = 0.597; p < 0.0001). Bland-Altman bias analysis was conducted, and the results showed that differences in IG% from XN and manual analysis for MN patients were considered clinically insignificant. ROC analysis demonstrated a good performance of IG# (AUC = 0.842) and IG% (AUC = 0.885) assessed by XN for MN patients with cut-off values of 0.200 × 109/L and 1.95%, respectively. IG parameters from Sysmex XN analyzer are helpful for screening of MNs even though granulocyte morphological abnormalities may interfere with IG parameter accuracy.

Circulatory Neutrophils Exhibit Enhanced Neutrophil Extracellular Trap Formation in Early Puerperium: NETs at the Nexus of Thrombosis and Immunity

Pregnancy is associated with elevated maternal levels of cell-free DNA of neutrophil extracellular trap (NET) origin, as circulatory neutrophils exhibit increased spontaneous NET formation, mainly driven by G-CSF and finely modulated by sex hormones. The postpartum period, on the other hand, involves physiological alterations consistent with the need for protection against infections and fatal haemorrhage. Our findings indicate that all relevant serum markers of neutrophil degranulation and NET release are substantially augmented postpartum. Neutrophil pro-NETotic activity in vitro is also upregulated particularly in post-delivery neutrophils. Moreover, maternal puerperal neutrophils exhibit a strong pro-NETotic phenotype, associated with increased levels of all key players in the generation of NETs, namely citH3, MPO, NE, and ROS, compared to non-pregnant and pregnant controls. Intriguingly, post-delivery NET formation is independent of G-CSF in contrast to late gestation and complemented by the presence of TF on the NETs, alterations in the platelet activity status, and activation of the coagulation cascade, triggered by circulating microparticles. Taken together, our results reveal the highly pro-NETotic and potentially procoagulant nature of postpartum neutrophils, bridging an overt immune activation with possible harmful thrombotic incidence.

Analysis of transcriptomic data sets supports the role of IL-6 in NETosis and immunothrombosis in severe COVID-19

Background

There is an urgent need to understand the key events driving pathogenesis of severe COVID-19 disease, so that precise treatment can be instituted. In this respect NETosis is gaining increased attention in the scientific community, as an important pathological process contributing to mortality. We sought to test if indeed there exists robust evidence of NETosis in multiple transcriptomic data sets from human subjects with severe COVID-19 disease. Gene set enrichment analysis was performed to test for up-regulation of gene set functional in NETosis in the blood of patients with COVID-19 illness.

Results

Blood gene expression functional in NETosis increased with severity of illness, showed negative correlation with blood oxygen saturation, and was validated in the lung of COVID-19 non-survivors. Temporal expression of IL-6 was compared between severe and moderate illness with COVID-19. Unsupervised clustering was performed to reveal co-expression of IL-6 with complement genes. In severe COVID-19 illness, there is transcriptional evidence of activation of NETosis, complement and coagulation cascade, and negative correlation between NETosis and respiratory function (oxygen saturation). An early spike in IL-6 is observed in severe COVID-19 illness that is correlated with complement activation.

Conclusions

Based on the transcriptional dynamics of IL-6 expression and its downstream effect on complement activation, we constructed a model that links early spike in IL-6 level with persistent and self-perpetuating complement activation, NETosis, immunothrombosis and respiratory dysfunction. Our model supports the early initiation of anti-IL6 therapy in severe COVID-19 disease before the life-threatening complications of the disease can perpetuate themselves autonomously.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12863-021-01001-1.

Gene-Specific Sex Effects on Susceptibility to Infectious Diseases

Inflammation is an integral part of defense against most infectious diseases. These pathogen-induced immune responses are in very many instances strongly influenced by host’s sex. As a consequence, sexual dimorphisms were observed in susceptibility to many infectious diseases. They are pathogen dose-dependent, and their outcomes depend on pathogen and even on its species or subspecies. Sex may differentially affect pathology of various organs and its influence is modified by interaction of host’s hormonal status and genotype: sex chromosomes X and Y, as well as autosomal genes. In this Mini Review we summarize the major influences of sex in human infections and subsequently focus on 22 autosomal genes/loci that modify in a sex-dependent way the response to infectious diseases in mouse models. These genes have been observed to influence susceptibility to viruses, bacteria, parasites, fungi and worms. Some sex-dependent genes/loci affect susceptibility only in females or only in males, affect both sexes, but have stronger effect in one sex; still other genes were shown to affect the disease in both sexes, but with opposite direction of effect in females and males. The understanding of mechanisms of sex-dependent differences in the course of infectious diseases may be relevant for their personalized management.