Neutrophil Populations Research Articles

­­­­­­­A type I IFN, prothrombotic hyperinflammatory neutrophil signature is distinct for COVID-19 ARDS­­­

Background: Acute respiratory distress syndrome (ARDS) is a severe critical condition with a high mortality that is currently in focus given that it is associated with mortality caused by coronavirus disease 2019 (COVID-19). Neutrophils play a key role in the lung injury characteristic of non-COVID-19 ARDS and there is also accumulating evidence of neutrophil mediated lung injury in patients who succumb to infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Methods: We undertook a functional proteomic and metabolomic survey of circulating neutrophil populations, comparing patients with COVID-19 ARDS and non-COVID-19 ARDS to understand the molecular basis of neutrophil dysregulation. Results: Expansion of the circulating neutrophil compartment and the presence of activated low and normal density mature and immature neutrophil populations occurs in ARDS, irrespective of cause. Release of neutrophil granule proteins, neutrophil activation of the clotting cascade and upregulation of the Mac-1 platelet binding complex with formation of neutrophil platelet aggregates is exaggerated in COVID-19 ARDS. Importantly, activation of components of the neutrophil type I interferon responses is seen in ARDS following infection with SARS-CoV-2, with associated rewiring of neutrophil metabolism, and the upregulation of antigen processing and presentation. Whilst dexamethasone treatment constricts the immature low density neutrophil population, it does not impact upon prothrombotic hyperinflammatory neutrophil signatures. Conclusions: Given the crucial role of neutrophils in ARDS and the evidence of a disordered myeloid response observed in COVID-19 patients, this work maps the molecular basis for neutrophil reprogramming in the distinct clinical entities of COVID-19 and non-COVID-19 ARDS.

Leukocyte TNFR1 and TNFR2 Expression Contributes to the Peripheral Immune Response in Cases with Ischemic Stroke.

Tumor necrosis factor receptor 1 and 2 (TNFR1 and TNFR2) have been found in brain parenchyma of stroke patients, and plasma levels are increased in the acute phase of stroke. We evaluated associations between TNFR1 and TNFR2 plasma levels and stroke severity, infarct size, and functional outcome. Furthermore, we examined cellular expression of TNFR1 and TNFR2 on leukocyte subpopulations to explore the origin of the increased receptor levels. Blood samples were taken from 33 acute ischemic stroke patients and 10 healthy controls. TNFR1 and TNFR2 plasma concentrations were measured and correlated against the Scandinavian Stroke Scale at admission, infarct volume, and the modified Rankin Scale score three months after stroke onset. Classical, intermediate, and non-classical monocytes as well as neutrophils were purified, and cellular expression of TNFR1 and TNFR2 was examined using flow cytometry. TNFR1 and TNFR2 plasma levels were both increased after ischemic stroke, but we found no correlation with patient outcome measurements. Compared to healthy controls, ischemic stroke patients had decreased non-classical monocyte and neutrophil populations expressing TNFR1 and increased neutrophils expressing TNFR2, and decreased non-classical populations co-expressing both TNFR1 and TNFR2. This study supports the hypothesis of an acute immunological response orchestrated by the peripheral immune system following an ischemic stroke. However, the origin of the increased TNFR1 and TNFR2 plasma levels could not be clearly linked to peripheral monocytes or neutrophils. Future studies are needed and will help clarify the potential role as treatment target.

Heterogeneity of neutrophils in arterial hypertension

Cellular heterogeneity and diversity are recognized to contribute to the functions of neutrophils under homeostatic and pathological conditions. We previously suggested that the chronic inflammatory responses associated with hypertension (HTN) are related to the participation of different subpopulations of neutrophils. Two populations of neutrophils can be obtained by density gradient centrifugation: normal-density neutrophils (NDN) and low-density neutrophils (LDN). However, the lack of standardized functional protocols has limited phenotypic characterization and functional comparisons of LDN and NDN.Based on their capability to incorporate Na+, maturity and activation stage, we characterized NDN and LDN in blood samples from ten patients with HTN and ten healthy individuals (HI) using flow cytometry. We compared the levels of reactive oxygen species (ROS), generation of neutrophil extracellular traps (NETs) and levels of apoptosis in NDN and LDN. In general, the NDN and LDN subpopulations from patients with HTN exhibited higher levels of sodium influx and ROS, and lower levels of apoptosis than the corresponding NDN and LDN subsets from HI. Transmission electron microscopy revealed NDN and LDN from patients with HTN exhibited alterations to mitochondrial morphology and fewer cytoplasmic granules than the corresponding HI subpopulations.Our results indicate both the NDN and LDN subpopulations enhance the effects of inflammation that contribute to the pathophysiology of HTN. Further detailed studies are required to characterize the events during ontogeny of the myeloid lineage that result in the diverse phenotypic characteristics of each subpopulation of LDN and NDN.

β2 Integrin Regulation of Neutrophil Functional Plasticity and Fate in the Resolution of Inflammation.

Neutrophils act as the first line of cellular defense against invading pathogens or tissue injury. Their rapid recruitment into inflamed tissues is critical for the elimination of invading microorganisms and tissue repair, but is also capable of inflicting damage to neighboring tissues. The β2 integrins and Mac-1 (CD11b/CD18, αMβ2 or complement receptor 3) in particular, are best known for mediating neutrophil adhesion and transmigration across the endothelium and phagocytosis of microbes. However, Mac-1 has a broad ligand recognition property that contributes to the functional versatility of the neutrophil population far beyond their antimicrobial function. Accumulating evidence over the past decade has demonstrated roles for Mac-1 ligands in regulating reverse neutrophil transmigration, lifespan, phagocytosis-induced cell death, release of neutrophil extracellular traps and efferocytosis, hence extending the traditional β2 integrin repertoire in shaping innate and adaptive immune responses. Understanding the functions of β2 integrins may partly explain neutrophil heterogeneity and may be instrumental to develop novel therapies specifically targeting Mac-1-mediated pro-resolution actions without compromising immunity. Thus, this review details novel insights on outside-in signaling through β2 integrins and neutrophil functional heterogeneity pertinent to the resolution of inflammation.

Dexmedetomidine mitigates lipopolysaccharide-induced acute lung injury in septic rats via inhibition of NF-κB associated anti-inflammatory pathway

Purpose: To investigate the effect of dexmedetomidine in a rat model of acute lung injury (ALI), and the underlying mechanism.
 Methods: Acute lung injury (ALI) was induced in adult male Sprague Dawley rats (n = 27) using lipopolysaccharide (LPS). Three rat groups were used (9 rats/group): untreated control, LPS and treatment groups. Pathological lesions in rat pulmonary tissues were assessed and inflammatory scores determined. The levels TNF-α and IL-6 in BALF were determined using their respective enzyme-linked immunosorbent assay (ELISA) kits, while protein levels of p-IκB and NF-κB p65 were assessed by Western blotting.
 Results: Lung tissue damage was markedly mitigated in treatment mice, relative to LPS mice (p < 0.05). Inflammatory scores and population of neutrophils and macrophages increased significantly in LPS mice, relative to control, but decreased by dexmedetomidine exposure (p < 0.05). Similarly, TNF-α and IL-6 levels in pulmonary tissue homogenates of LPS rats were increased, relative to control rats, but were downregulated by dexmedetomidine exposure (p < 0.05). Moreover, dexmedetomidine downregulated the expressions of p-IκB and NF-κB p65 in pulmonary tissues (p < 0.05).
 Conclusion: Dexmedetomidine mitigates LPS-induced ALI in rats by blocking the activation of NF-κB and IκB, coupled with inhibition of the secretion of TNF-α and IL-6.
 Keywords: Acute lung injury, Dexmedetomidine, Inflammatory cytokines, NF-κB pathway, Sepsis

Abstract LT010: Pleiotrophin drives pro-metastatic immune niche within breast tumor microenvironment

Abstract Background: Pleiotrophin (PTN), a heparin binding cytokine important during embryonic development, is expressed at elevated levels in several cancers, including breast cancer. High PTN expression in serum and tumor tissues of breast cancer patients correlates with worse outcome. Previous studies indicate PTN contributes to angiogenesis, hematopoiesis, and inflammation; however, the function of PTN in breast cancer progression and metastasis has not been elucidated. Methods: The effect of anti-PTN therapy (mAb; 3B10) on breast tumor progression and pulmonary metastasis was evaluated in four preclinical models of breast cancer: 4T1, E0771, Met-1, MMTV-PyMT. In addition, the effect of global loss of PTN using Ptn-deficient mice was evaluated in two murine models of breast cancer. Tissues from these experiments were analyzed by RNAseq and histology for changes in angiogenesis, hematopoiesis, immune cell infiltration, and cytokine/chemokine expression. Findings: TCGA data shows high PTN expression correlates with poor survival of Stage IV breast cancer patients. Furthermore, our data indicate that: a) blocking PTN pharmacologically or genetically results in a significant reduction of lung metastasis in multiple preclinical mouse models of breast cancer, b) scRNAseq and dual FISH-IHC (fluorescence in-situ hybridization and immunohistochemistry) demonstrates that endothelial cells and select population of tumor cells express PTN in the tumor microenvironment (TME), c) inhibition of PTN results in a decrease in overall inflammation with a particular decrease in neutrophil populations at primary and secondary tumor sites, d) in a genetically engineered mouse model (GEMM) of breast cancer, MMTV-PyMT, PTN expression is enriched at the metastatic site. Conclusion: Our data suggests that PTN is important in driving a pro-metastatic immune niche within the TME that promotes tumor cell escape from the primary tumor and survival of metastatic cancer cells in secondary sites. Additionally, our studies highlight that inhibition of PTN has potential to reduce metastatic burden in breast cancer and suggest that future studies testing the combination of PTN inhibition with standard chemotherapy or immune therapy are warranted. Citation Format: Debolina Ganguly, Noah Sorrelle, Adrian Dominguez, Jason Toombs, Marcel Schmidt, Fa Valdes Mora, David Gallego Ortega, Anton Wellstein, Rolf A. Brekken. Pleiotrophin drives pro-metastatic immune niche within breast tumor microenvironment [abstract]. In: Proceedings of the AACR Virtual Special Conference on the Evolving Tumor Microenvironment in Cancer Progression: Mechanisms and Emerging Therapeutic Opportunities; in association with the Tumor Microenvironment (TME) Working Group; 2021 Jan 11-12. Philadelphia (PA): AACR; Cancer Res 2021;81(5 Suppl):Abstract nr LT010.

Impact of SARS-CoV-2 infection on the recovery of peripheral blood mononuclear cells by density gradient

SARS-CoV-2 virus infection is responsible for coronavirus disease (COVID-19), which is characterised by a hyperinflammatory response that plays a major role in determining the respiratory and immune-mediated complications of this condition. While isolating peripheral blood mononuclear cells (PBMCs) from whole blood of COVID-19 patients by density gradient centrifugation, we noticed some changes in the floating properties and in the sedimentation of the cells on density medium. Investigating this further, we found that in early phase COVID-19 patients, characterised by reduced circulating lymphocytes and monocytes, the PBMC fraction contained surprisingly high levels of neutrophils. Furthermore, the neutrophil population exhibited alterations in the cell size and in the internal complexity, consistent with the presence of low density neutrophils (LDNs) and immature forms, which may explain the shift seen in the floating abilities and that may be predictive of the severity of the disease. The percentage of this subset of neutrophils found in the PBMC band was rather spread (35.4 ± 27.2%, with a median 28.8% and IQR 11.6–56.1, Welch’s t-test early phase COVID-19 versus blood donor healthy controls P < 0.0001). Results confirm the presence of an increased number of LDNs in patients with early stage COVID-19, which correlates with disease severity and may be recovered by centrifugation on a density gradient together with PBMCs.

-------A type I IFN, prothrombotic hyperinflammatory neutrophil signature is distinct for COVID-19 ARDS--.

Background: Acute respiratory distress syndrome (ARDS) is a severe critical condition with a high mortality that is currently in focus giventhat it is associated with mortality caused by coronavirus disease 2019 (COVID-19). Neutrophils play a key role in the lung injury characteristic of non-COVID-19 ARDS and there is also accumulating evidence of neutrophil mediated lung injury in patients who succumb to infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Methods: We undertook a functional proteomic and metabolomic survey of circulating neutrophil populations, comparing patients with COVID-19 ARDS and non-COVID-19 ARDS to understand the molecular basis of neutrophil dysregulation. Results: Expansion of the circulating neutrophil compartment and the presence of activated low and normal density mature and immature neutrophil populations occurs in ARDS, irrespective of cause. Release of neutrophil granule proteins, neutrophil activation of the clotting cascade and upregulation of the Mac-1 platelet binding complex with formation of neutrophil platelet aggregates is exaggerated in COVID-19 ARDS. Importantly, activation of components of the neutrophil type I interferon responses is seen in ARDS following infection with SARS-CoV-2, with associated rewiring of neutrophil metabolism, and the upregulation of antigen processing and presentation. Whilst dexamethasone treatment constricts the immature low density neutrophil population, it does not impact upon prothrombotic hyperinflammatory neutrophil signatures. Conclusions: Given the crucial role of neutrophils in ARDS and the evidence of a disordered myeloid response observed in COVID-19 patients, this work maps the molecular basis for neutrophil reprogramming in the distinct clinical entities of COVID-19 and non-COVID-19 ARDS.

Transcriptional Diversity and Niche-Specific Distribution of Leukocyte Populations during Staphylococcus aureus Craniotomy-Associated Biofilm Infection.

Neurosurgery for brain tumor resection or epilepsy treatment requires a craniotomy to gain access to the brain. Despite prophylactic measures, infectious complications occur at a frequency of 1-3%, with approximately half caused by Staphylococcus aureus (S. aureus) that forms a biofilm on the bone flap and is recalcitrant to antibiotics. Using single-cell RNA sequencing in a mouse model of S. aureus craniotomy infection, this study revealed the complex transcriptional heterogeneity of resident microglia and infiltrating monocytes in the brain, in addition to transcriptionally diverse granulocyte subsets in the s.c. galea and bone flap. In the brain, trajectory analysis identified the transition of microglia from a homeostatic/anti-inflammatory to proinflammatory and proliferative populations, whereas granulocytes in the brain demonstrated a trajectory from a granulocyte myeloid-derived suppressor cell (MDSC)-like phenotype to a small population of mature polymorphonuclear neutrophils (PMNs). In the galea, trajectory analysis identified the progression from two distinct granulocyte-MDSC-like populations to PMN clusters enriched for IFN signaling and cell cycle genes. Based on their abundance in the galea and bone flap, PMNs and MDSCs were depleted using anti-Ly6G, which resulted in increased bacterial burden. This revealed a critical role for PMNs in S. aureus containment because MDSCs were found to attenuate PMN antibacterial activity, which may explain, in part, why craniotomy infection persists in the presence of PMN infiltrates. These results demonstrate the existence of a transcriptionally diverse leukocyte response that likely influences the chronicity of S. aureus craniotomy infection.

IMMATURE LOW-DENSITY NEUTROPHILS AS MEDIATORS OF PYODERMA GANGRENOSUM AND INFLAMMATORY BOWEL DISEASE PATHOGENESIS

Pyoderma gangrenosum (PG) is a debilitating skin condition characterized by deep, pus-filled, non-healing ulcers packed with neutrophils and is a common extraintestinal manifestation of inflammatory bowel disease (IBD). Strikingly, ∼40% of people with an initial presentation of PG go on to be also diagnosed with IBD, suggesting that both diseases have common factors driving their pathogenesis. The molecular and cellular mechanisms of PG and IBD co-development are currently unknown, hampering the development of effective treatment strategies for individuals affected by both diseases. Prior studies of individuals with PG demonstrate an enrichment of circulating immature low-density neutrophils (LDGs) that are sensitized to undergo NETosis, a specialized form of cell death. NETosis induces inflammation and, when dysregulated, can promote chronic cycles of inflammation. We hypothesize that LDGs mediate NETosis-driven inflammation in both PG and IBD, but the LDGs from individuals that develop both diseases are functionally distinct. In this translational study, blood samples are collected from healthy subjects or individuals with only PG, only Crohn’s disease, only ulcerative colitis, or individuals with both PG and IBD for the analysis of neutrophil populations, neutrophil function, as well as circulating markers of inflammation and NETosis. Preliminary data from 45 subjects demonstrate an enrichment of circulatory LDGs (CD45+ CD15+ CD66b+ CD10+ CD16+ cells from the low density fraction) in individuals with inflammatory disease as compared to healthy subjects (19.2% +/- 2.81%, n=41 vs. 9.9% +/- 2.9%, n=4; p=0.04). This is correlated with increased NETosis in vitro, however differences in the responsiveness of LDGs to priming signals, such as IL-1β, TNFα, and IL-6, are emerging between disease sub-groups. There is considerable variation in the levels of LDGs within disease sub-groups and analyses are underway to determine whether this variation correlates with subject reported disease activity, inflammatory markers (serum C-reactive protein), or circulating markers of NETosis (serum citrullinated histone 3). These preliminary findings point to the presence of a unique population of cells potentially contributing to inflammatory cross-talk between the skin and gut. Further analysis of these potentially disease driving cells may result in more effective care of IBD patients with extraintestinal manifestations, such as PG, through more mechanistically targeted therapeutic approaches, as well as potential biomarker discovery that predicts which PG patients are more likely to develop IBD leading to earlier intervention and better disease outcomes.

Dietary exposure to chlorpyrifos affects systemic and hepatic immune-cell phenotypes in diabetic mice

Hyperglycemia induces low-grade systemic inflammation and immune dysregulation, leading to overstated reactions to immune stimuli and diabetes-related organ damage. Tissue inflammation is characterized by leukocyte infiltration, and T cells play crucial roles in directing leukocyte-mediated inflammatory responses. The aim of the study was to investigate the effects of dietary exposure to chlorpyrifos (CPF) on systemic and hepatic immune-cell phenotypes in C57BL/6 mice with streptozotocin (STZ)-induced diabetes. Mice received an intraperitoneal injection of STZ for 5 consecutive days to induce diabetes, and diabetic mice were given either an AIN-93-based control diet or a CPF-containing diet at doses of 0.5, 1, or 2 mg/kg body weight/day for 28 days. Results showed that dietary exposure to CPF had no influence on the body weight or the erythrocyte hemoglobin A1c level in diabetic mice. Both blood and hepatic neutrophil populations were enhanced by CPF exposure. CPF-exposed groups had lower percentages of blood T cells without altering the proportions of CD4+ and CD8+ T-cell subsets, and lower expression levels of the Bcl-2 antiapoptotic gene in the spleen. CPF exposure reduced the percentage of blood regulatory T cells (Tregs); however, the Treg population was upregulated in the liver even when hepatic T cells were not affected by CPF in diabetic mice. Hepatic expressions of Treg-related genes were suppressed in all CPF-exposed groups. Higher plasma levels of aspartate aminotransferase and expression levels of the hepatic interleukin-1β gene were observed in diabetic mice exposed to medium and high doses of CPF. These findings suggest that dietary exposure to CPF affects the distribution of both myeloid and lymphoid immune cells in the blood and liver under hyperglycemic conditions, which may lead to hyperinflammation when encountering immune stimuli.

IMMATURE LOW-DENSITY NEUTROPHILS AS MEDIATORS OF PYODERMA GANGRENOSUM AND INFLAMMATORY BOWEL DISEASE PATHOGENESIS

Abstract Pyoderma gangrenosum (PG) is a debilitating skin condition characterized by deep, pus-filled, non-healing ulcers packed with neutrophils and is a common extraintestinal manifestation of inflammatory bowel disease (IBD). Strikingly, ~40% of people with an initial presentation of PG go on to be also diagnosed with IBD, suggesting that both diseases have common factors driving their pathogenesis. The molecular and cellular mechanisms of PG and IBD co-development are currently unknown, hampering the development of effective treatment strategies for individuals affected by both diseases. Prior studies of individuals with PG demonstrate an enrichment of circulating immature low-density neutrophils (LDGs) that are sensitized to undergo NETosis, a specialized form of cell death. NETosis induces inflammation and, when dysregulated, can promote chronic cycles of inflammation. We hypothesize that LDGs mediate NETosis-driven inflammation in both PG and IBD, but the LDGs from individuals that develop both diseases are functionally distinct. In this translational study, blood samples are collected from healthy subjects or individuals with only PG, only Crohn’s disease, only ulcerative colitis, or individuals with both PG and IBD for the analysis of neutrophil populations, neutrophil function, as well as circulating markers of inflammation and NETosis. Preliminary data from 45 subjects demonstrate an enrichment of circulatory LDGs (CD45+ CD15+ CD66b+ CD10+ CD16+ cells from the low density fraction) in individuals with inflammatory disease as compared to healthy subjects (19.2% +/- 2.81%, n=41 vs. 9.9% +/- 2.9%, n=4; p=0.04). This is correlated with increased NETosis in vitro, however differences in the responsiveness of LDGs to priming signals, such as IL-1β, TNFα, and IL-6, are emerging between disease sub-groups. There is considerable variation in the levels of LDGs within disease sub-groups and analyses are underway to determine whether this variation correlates with subject reported disease activity, inflammatory markers (serum C-reactive protein), or circulating markers of NETosis (serum citrullinated histone 3). These preliminary findings point to the presence of a unique population of cells potentially contributing to inflammatory cross-talk between the skin and gut. Further analysis of these potentially disease driving cells may result in more effective care of IBD patients with extraintestinal manifestations, such as PG, through more mechanistically targeted therapeutic approaches, as well as potential biomarker discovery that predicts which PG patients are more likely to develop IBD leading to earlier intervention and better disease outcomes.

Indicators of immunosuppression peripartum in dual purpose cows in the tropics affected health, productive and reproductive parameters.

The objective of the study was to identify immunosuppression peripartum indicators in dual purpose cows in the tropics and determine their effects on productive and reproductive parameters. The indicators used were: changes in leukocyte and neutrophils population, concentrations of energy metabolites (β-hydroxybutyrate and glucose) and body condition scores (BCS). Blood sampling and BCS (scale 1 – 5) were taken weekly during the peripartum. Uterine health was assessed (3 weeks postpartum) by ultrasonography and using a vaginal score (0-3) described by Sheldon et al. (2006). Cows (n=30) were classified as healthy or clinical endometritis (CE). CE prevalence was as high as 29.6%. Leukocyte and neutrophils populations diminished while in the peripartum and were lower (P<0.05) in cows suffering CE. Healthy cows had higher (P<0.05) daily milk production than those with CE (18.84±0.63 vs 14.76±0.84 kg). CE cows had lower (P<0.05) reproductive performance compared with healthy cows (open days: 244.40 ± 35.00 vs 178.00 ± 23.33 and services by conception 3.33 ± 0.51 vs 1.83 ± 0.34). BCS similarly (P>0.05) decreased following parturition in both groups. Concentrations of energy metabolites during peripartum fluctuated in a similar (P>0.05) manner in healthy and CE cows. In summary, dual purpose cows in tropical conditions, presented peripartum immunosuppression indicators, characterized by a decline in the leukocyte population, mainly neutrophils, as well as decreased glucose concentrations and BCS postpartum. In addition to it, there was a rise in the β-hydroxybutyrate concentrations and cows presenting CE had a negative effect in the productive and reproductive parameters.

The Innate and Adaptive Immune Landscape of SARS-CoV-2-Associated Multisystem Inflammatory Syndrome in Children (MIS-C) from Acute Disease to Recovery

Multisystem inflammatory syndrome in children (MIS-C) is a life-threatening disease occurring several weeks after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. MIS-C has overlapping clinical features with Kawasaki Disease (KD), a rare childhood vasculitis, but whether these diseases share underpinning immunological perturbations is unknown. Deep immune profiling showed acute MIS-C patients had highly activated neutrophils, classical monocytes and memory CD8+ T-cells; increased frequencies of B-cell plasmablasts and double-negative B-cells; and increased cytokine levels. Post treatment samples from the same patients, taken when symptoms were resolving, identified recovery-associated immune features including CD163+ monocytes, emergence of a new population of immature neutrophils and, in some patients, a transient increase in arginase. Our data show MIS-C and KD share substantial immunopathology during the acute and recovery stages of disease and identify potential new mechanisms of action for IVIG, a widely used anti-inflammatory drug used to treat MIS-C, KD and other inflammatory diseases.

The Functional Heterogeneity of Neutrophil-Derived Extracellular Vesicles Reflects the Status of the Parent Cell.

Similar to other cell types, neutrophilic granulocytes also release extracellular vesicles (EVs), mainly medium-sized microvesicles/microparticles. According to published data, authors have reached a consensus on the physical parameters (size, density) and chemical composition (surface proteins, proteomics) of neutrophil-derived EVs. In contrast, there is large diversity and even controversy in the reported functional properties. Part of the discrepancy may be ascribed to differences in the viability of the starting cells, in eliciting factors, in separation techniques and in storage conditions. However, the most recent data from our laboratory prove that the same population of neutrophils is able to generate EVs with different functional properties, transmitting pro-inflammatory or anti-inflammatory effects on neighboring cells. Previously we have shown that Mac-1 integrin is a key factor that switches anti-inflammatory EV generation into pro-inflammatory and antibacterial EV production. This paper reviews current knowledge on the functional alterations initiated by neutrophil-derived EVs, listing their effects according to the triggering agents and target cells. We summarize the presence of neutrophil-derived EVs in pathological processes and their perspectives in diagnostics and therapy. Finally, the functional heterogeneity of differently triggered EVs indicates that neutrophils are capable of producing a broad spectrum of EVs, depending on the environmental conditions prevailing at the time of EV genesis.

Essential Role of Neutrophils in the Protective Immune Response Induced by a Live Attenuated Leishmania Vaccine.

No licensed vaccine exists against visceral leishmaniasis (VL), a disease caused by the Leishmania donovani parasite. We have previously reported both macrophages and dendritic cells play important role in the protection induced by a live attenuated centrin gene-deleted L. donovani (LdCen-/- ) parasite vaccine. The role of neutrophils in orchestrating the initial innate response to pathogens is widely recognized. To investigate the early interaction of LdCen-/- with neutrophils, we immunized mice intradermally in the ear pinna with LdCen-/- Compared with LdWT infection, LdCen-/- parasites induced higher recruitment of neutrophils to the ear dermis and ear draining lymph nodes (dLN) as early as 6-18 h after immunization, which were predominantly proinflammatory in nature. Neutrophils from ear dLN of LdCen-/- -immunized mice exhibited heightened expression of costimulatory molecules and attenuated expression of coinhibitory molecules necessary for higher T cell activation. Further phenotypic characterization revealed heterogeneous neutrophil populations containing Nα and Nβ subtypes in the ear dLN. Of the two, the parasitized Nα subset from LdCen-/- -immunized mice exhibited much stronger Ag-specific CD4+ T cell proliferation ex vivo. Adoptive transfer of neutrophils bearing LdCen-/- parasites induced an increased Th1 response in naive mice. Importantly, neutrophil depletion significantly abrogated Ag-specific CD4+ T cell proliferation in LdCen-/- -immunized mice and impaired protection against virulent challenge. Conversely, replenishing of neutrophils significantly restored the LdCen-/- -induced host-protective response. These results suggest that neutrophils are indispensable for protective immunity induced by LdCen-/- parasite vaccine.

СОСТОЯНИЕ МУКОЗАЛЬНОГО ИММУНИТЕТА У ДЕТЕЙ С ВНЕБОЛЬНИЧНОЙ ПНЕВМОНИЕЙ НА ФОНЕ СНИЖЕННОЙ РЕЗИСТЕНТНОСТИ ОРГАНИЗМА

Objective of the research: in-depth study of local immunity indices in children with recurrent respiratory diseases (RRD) who fell ill with community-acquired pneumonia (CAP) to optimize immunotherapy. Materials and methods: 83 children aged 3 to 7 years with CAP were under observation. The main group included 50 children with RRD who fell ill with CAP. The comparison group included 33 preschool children with good body's resistance (not belonging to the group of frequently ill children with IR values of 0,2–0,3) who fell ill with CAP. Methods: the indicators of mucosal immunity of induced sputum with an assessment of its cellular composition, the severity of destructive changes in the neutrophil population and phagocytic activity of neutrophilic granulocytes were studied. Intraleukocyte microbicidal system of neutrophil, the level of main classes immunoglobulins and sIgA were assessed. The local cytokine profile was studied by the content of pro-inflammatory and anti-inflammatory cytokines (IL-4, IL-8, IL-10, TNFα, IFNγ). Results: the study revealed a pronounced imbalance between different functional characteristics of neutrophilic granulocytes – along with depression of neutrophil release in children with RRD, there is an increase in the number of neutrophils with signs of nucleus and cytoplasm destruction. Inhibition of cytotoxic activity, manifested by a decrease in oxygen-dependent biocidal activity and inhibition of the intraleukocytic microbicidal system of neutrophils was revealed. It was shown that inhibition of immunoglobulins synthesis and imbalance in the system of local synthesis of pro-inflammatory and anti-inflammatory cytokines are important factors in the disorders of local mucosal profile. Against the background of the revealed disorders of mucosal immunity, there is a longer dynamics of relief of main CAP clinical and radiological symptoms in children with RRD, which provides a scientific justification for the including of immunocorrective therapy in the treatment complex for these patients.

Development and characterization of a novel autochthonous semi-spontaneous bladder cancer model by pathological evaluation, single cell sequencing and proteomic profiling

There is scarce knowledge of the molecular events of recurrence and progression in non-muscle invasive bladder cancer (NMIBC). The heterogeneity of patients’ clinical disease impacts the use of molecular tools and hampers therapeutic strategies. To improve the understanding of tumor development and progression in the native microenvironment, we induced and profiled an autochthonous bladder cancer model. 0.05% OH-BBN was administrated in drinking water to Hgf-Cdk4(R24C) mice for 10 weeks. Histopathology evaluation of tissue, single cell RNA sequencing, and urine and serum proteomics by the Proximity Extension Assay were performed. Therapeutic studies (anti-PD1, CpG ODN) were performed at the NMIBC stage and on a transplanted novel cell line. Exposure of transgenic animals to OH-BBN for 10 weeks led to urothelial NMIBC that differed from exposed wt C57BL/6 mice, while females developed T1 tumors faster than males. Tumors were of Tis/T1 stage with squamous differentiation and within 10 weeks progressed to muscle invasive bladder cancer (MIBC). Single cell sequencing displayed three malignant or premalignant cell clusters with distinct molecular profiles trending towards the luminal or basal subtype and genomic instability. Carcinogen induced bladders presented a clear change in neutrophil, macrophage and fibroblast populations. Anti-PD1 monotherapy at NMIBC did not protect animals from progression, but a possible delay in tumor growth was seen in females. Sex differences in proteomic profiles of urine and serum were obvious, however indicators of myeloid cell recruitment to the tumor microenvironment were shared. Subcutaneous tumors of an outgrown Hgf-Cdk4(R24C) tumor derived cell line were significantly controlled using CpG ODN treatment only in female mice. Hgf-Cdk4(R24C) mice develop NMIBC upon OH-BBN exposure and progress to MIBC. Female animals present more rapid tumor establishment than males. Single cell RNA sequencing revealed the coexistence of heterogeneous tumor cell populations. Sex specific differences appeared in tumor growth, proteomic profiling and therapeutic outcome and should be further explored.

Synergistic Roles of Macrophages and Neutrophils in Osteoarthritis Progression.

To evaluate the role of immune cells and their effector cytokines in the pathogenesis and progression of knee osteoarthritis (OA) in matched OA synovial fluid (SF) and synovial tissue samples. Cells from matched samples of synovial tissue and SF acquired from individuals undergoing total knee replacement for OA (n = 39) were characterized for immune cell-associated surface markers and intracellular cytokine expression using polychromatic flow cytometry. Additional individuals with radiographic knee OA (Kellgren/Lawrence severity grades ≥1) who had available etarfolatide (inflammatory cell) imaging (n = 26) or baseline and 3-year data on progression of radiographic knee OA (n = 85) were also assessed. SF cytokine concentrations in all cohorts were evaluated for associations with synovial tissue and SF cell phenotypes and severity of radiographic knee OA. Macrophages (predominant in the synovial tissue, 53% of total cells) and neutrophils (predominant in the SF, 26% of total cells) were the major immune cell populations identified in the OA knee joints, exhibiting expression of or association with transforming growth factor β1 (TGFβ1) and elastase, respectively, in the SF. Expression levels of TGFβ1 and elastase were significantly associated with severity of radiographic knee OA. Baseline SF concentrations of TGFβ1 and elastase along with radiographic knee OA severity scores were predictive of knee OA progression, with areas under the receiver operating characteristic curves of 0.810 (for TGFβ1), 0.806 (for elastase), and 0.846 (for both TGFβ1 and elastase combined), with greater stability of prediction when both markers were utilized. Our findings demonstrate the hitherto underappreciated role of neutrophils in the sterile inflammatory process and progression of OA. Two soluble mediators, SF elastase and TGFβ1, are strong predictors of knee OA progression, reflecting a synergistic role of neutrophil and macrophage populations in the pathogenesis and worsening of OA that could potentially be utilized to identify patients who may have a greater risk of more rapid disease progression.

Analyzing Risk of Infection with Anti-CD38 Monoclonal Antibody Therapy for Patients with Multiple Myeloma

Monoclonal antibodies targeting CD38 are emerging as a mainstay of therapy for Multiple Myeloma (MM) in the relapse setting as well as upfront. These antibodies not only target CD38 on myeloma cells inducing anti-tumor pleiotropic effects, they also influence normal CD38-expressing cells, including normal plasma cells, natural killer cells and immunosuppressive regulatory cells (van de Donk et al , 2018). These cells play a key role in innate as well as humoral immunity and provide protection against a variety of infectious insults; hence, their depletion in MM patients (pts) can be expected to have deleterious immunological effects due to the dismantling of an effective immune responses in a population already strained by dysfunctional immunity. While it has been previously shown that NK cells decline with exposure to daratumumab (DARA) (Casneuf et al , 2017), its clinical impact on the incidence of infection has yet to be elucidated because clinical trials have shown conflicting results, while POLLUX and CASTOR trials showed generally similar rates of grade 3 or 4 infections (28·3% vs. 22·8% and 21·4% vs. 19·0%, respectively, the ALCYONE trial, reported that grade 3-4 infections were higher in the DARA arm (23·1% vs. 14·7%). Here, we aim to explore the impact of different risk factors on infection during DARA therapy. Methods: We retrospectively reviewed patient records who received DARA-containing regimens for MM between Jan 2016 and Jan 2020. The history of infection, prior therapies, rate of infection during therapy with DARA, hospitalizations, baseline and nadir absolute counts of lymphocyte, monocyte and neutrophil population were extracted. Pts who had less than 1 month of DARA were excluded. Survival was measured from time of DARA start. Survival distribution was estimated using Kaplan-Meier methods and differences of OS, PFS between groups was examined by Wilcoxon test. The effect of treatment on OS and PFS was estimated using a Cox model after controlling for the effects of different variables. Results: Of 123 pts reviewed, median line of therapy was 3 (range: 0-9). Median time from diagnosis was 52 months (range: 0- 232 months). 43 pts (35%) were Black and 77 (63%) Caucasian. Median age was 70 (range 34-94 y/o). 86 (70%) were IgG, 24 were IgA (20%) and 10 light chain myeloma (10%). 24 (20%) had stage I, 37 (30%) had stage II and 61 (50%) had ISS stage III. 66 (53%) pts had transplant as prior therapy and the rest did not undergo transplant. 29 (24%) pts had DARA as a single agent, 66 (53%) in combination with IMiDs and 28 (23%) pts in combination with PI. Median duration of therapy was 133 days (range 30-1245 days). Median ANC 1243 /ml (range: 420-1120). Median ALC 710 /mL (170-8020). Median AMC was 455 /mL (0-2300). 31 pts had history of prior infections and the rest did not. 39 pts had infection during DARA. Overall, there were 125 hospital admission encounters for whole cohort occurred in 36% of cases, more than half of them (55%) were attributable to an infectious process. Bacterial pathogens accounted for the majority of infection. Pts with infection during DARA therapy had statistically significant nadir ALC (median 560 /ml) compared to pts without any infection. The univariate analysis showed age, history of infection, nadir ALC less than 600/ml and number of prior line of therapy as significant factors associated with infection rate during DARA therapy. Multivariate analysis after controlling for these factors shows only Low nadir ALC less than 600 /ml, hazard ratio (HR): 2.15, 95% confidence interval (CI): 1.19-3.76, and history of infection, HR: 1.87, 95% CI: 1.11-2.92, stands out as statistically significant factor. The whole cohort were divided based on ALC&amp;lt;600 during the therapy or history of previous infection; the group with none of these two risk factors was assigned as low risk, the group with either of those as intermediate risk and the pts with both risk factor were characterized as high-risk group (Figure-1). Conclusion: Here we showed that infections is frequent among MM pts treated with DARA-containing regimen and assessed risk factors associated infection during DARA therapy. Dropping ALC and history of prior infection are significant factors associated with higher risk of infection during DARA therapy. These finding suggests vigilance for, and identification of risk factor are warranted for treating MM patient with DARA. The risk model is warranted to be examined in a prospective study. Disclosures de Lima: Pfizer: Other: Personal fees, advisory board, Research Funding; BMS: Other: Personal Fees, advisory board; Incyte: Other: Personal Fees, advisory board; Kadmon: Other: Personal Fees, Advisory board; Celgene: Research Funding. Malek:Cumberland: Research Funding; Takeda: Other: Advisory board , Speakers Bureau; Bluespark: Research Funding; Sanofi: Other: Advisory board; Clegene: Other: Advisory board , Speakers Bureau; Amgen: Honoraria; Medpacto: Research Funding; Janssen: Other: Advisory board, Speakers Bureau.