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The advent of recent cutting-edge technologies has allowed the discovery and characterization of novel progenitors of human neutrophils, including SSCloCD66b+CD15+CD11b−CD49dhiproNeu1s, SSChiCD66b+CD15+CD11b−CD49dintproNeus2s, CD66b+CD15+CD11b+CD49d+CD101−preNeus, and Lin−CD66b+CD117+CD71+eNePs. In this research field, we recently identified CD66b−CD38+CD64dimCD115−, CD34+, and CD34dim/− cells exclusively committed to the neutrophil lineage (which we renamed as CD34+ and CD34dim/− neutrophil-committed progenitors), representing the earliest neutrophil precursors identifiable and sorted by flow cytometry. Moreover, based on their differential CD34 and CD45RA expression, we could identify 4 populations of neutrophil-committed progenitors: CD34+CD45RA−/NCP1s, CD34+CD45RA+/NCP2s, CD34dim/−CD45RA+/NCP3s, and CD34dim/−CD45RA−/NCP4s. This said, a very recent study by Ikeda and coworkers (PMID: 36862552) reported that neutrophil precursors, termed either neutrophil progenitors or "early neutrophil-committed progenitors," would generate immunosuppressive neutrophil-like CXCR1+CD14+CD16− monocytes. Hence, presuming that neutrophil progenitors/"early neutrophil-committed progenitors" correspond to neutrophil-committed progenitors, the selective neutrophil commitment that we attributed to neutrophil-committed progenitors is contradicted by Ikeda and coworkers' article. In this study, by performing a more analytical reevaluation at the phenotypic and molecular levels of the cells generated by neutrophil-committed progenitors 2 and 4 (selected as representatives of neutrophil-committed progenitors), we categorically exclude that neutrophil-committed progenitors generate neutrophil-like CXCR1+CD14+CD16− monocytes. Rather, we provide substantial evidence indicating that the cells generated by neutrophil progenitors/"early neutrophil-committed progenitors" are neutrophilic cells at a different stage of maturation, displaying moderate levels of CD14, instead of neutrophil-like CXCR1+CD14+CD16− monocytes, as pointed by Ikeda and coworkers. Hence, the conclusion that neutrophil progenitors/"early neutrophil-committed progenitors" aberrantly differentiate into neutrophil-like monocytes derives, in our opinion, from data misinterpretation. This work provides further evidence that human neutrophil-committed progenitors treated with SCF, FLT3L, and G-CSF do not generate monocytes. [ABSTRACT FROM AUTHOR]

Discoveries made in the past decades have brought out that, in addition to their classical primary defensive functions against infections, polymorphonuclear neutrophils play key effector roles not only in chronic inflammatory and immune-mediated diseases but also in cancer. In addition, depending on their differentiation/activation status and/or on the physiological or pathological microenvironment in which they reside, neutrophils have been shown to behave as highly plastic cells, able to acquire new phenotypes/functional states. All these features are well manifested in cancer and modulated during tumor progression. Herein, we discuss intriguing data by Lai Ng's group that have shed light on the origin and development of terminally differentiated, proangiogenic, tumor-associated neutrophils, facilitating tumor growth in a murine orthotopic model of pancreatic ductal adenocarcinoma. These findings help to progress toward the ambitious goal of selectively targeting only the skewed pathological neutrophil populations present within the tumor microenvironment. This News and Views article comments on recent data demonstrating that murine neutrophils, upon tumor entry, are reprogrammed into a final population able to prolong their survival and promote neovascularization (https://doi.org/10.1126/science.adf6493). [ABSTRACT FROM AUTHOR]

Introduction: Peripheral monocytes in humans are conventionally divided into classical (CL, CD14++CD16− ), intermediate (INT, CD14++CD16+) and nonclassical (NC, CD14dim/− CD16++) cells, based on their expression levels of CD14 and CD16. A major fraction of the NC-monocytes has been shown to express the 6-sulfo LacNAc (slan) antigen, but whether these slan+/NCmonocytes represent the prototypical non-classical monocytes or whether they are simply a sub-fraction with identical features as the remainder of NC monocytes is still unclear. Methods: We analyzed transcriptome (by bulk and single cell RNA-seq), proteome, cell surface markers and production of discrete cytokines by peripheral slan+/NC- and slan− /NC-monocytes, in comparison to total NC-, CL- and INT- monocytes. Results: By bulk RNA-seq and proteomic analysis, we found that slan+/NCmonocytes express higher levels of genes and proteins specific of NCmonocytes than slan− /NC-monocytes do. Unsupervised clustering of scRNAseq data generated one cluster of NC- and one of INT-monocytes, where all slan+/NC-monocytes were allocated to the NC-monocyte cluster, while slan− / NC-monocytes were found, in part (13.4%), within the INT-monocyte cluster. In addition, total NC- and slan− /NC-monocytes, but not slan+/NC-monocytes, were found by both bulk RNA-seq and scRNA-seq to contain a small percentage of natural killer cells. Conclusion: In addition to comparatively characterize total NC-, slan− /NC- and slan+/NC-monocyte transcriptomes and proteomes, our data prove that slan+/ NC-, but not slan− /NC-, monocytes are more representative of prototypical NC-monocytes. [ABSTRACT FROM AUTHOR]

Granulomatosis with polyangiitis (GPA) is a systemic necrotizing vasculitis that is associated with granulomatous inflammation and the presence of anti-neutrophil cytoplasmic antibodies (ANCAs) directed against proteinase 3 (PR3). We previously determined that PR3 on the surface of apoptotic neutrophils interferes with induction of antiinflammatory mechanisms following phagocytosis of these cells by macrophages. Here, we demonstrate that enzymatically active membrane-associated PR3 on apoptotic cells triggered secretion of inflammatory cytokines, including granulocyte CSF (G-CSF) and chemokines. This response required the IL-1R1/MyD88 signaling pathway and was dependent on the synthesis of NO, as macrophages from animals lacking these pathways did not exhibit a PR3-associated proinflammatory response. The PR3-induced microenvironment facilitated recruitment of inflammatory cells, such as macrophages, plasmacytoid DCs (pDCs), and neutrophils, which were observed in close proximity within granulomatous lesions in the lungs of GPA patients. In different murine models of apoptotic cell injection, the PR3-induced microenvironment instructed pDC-driven Th9/Th2 cell generation. Concomitant injection of anti-PR3 ANCAs with PR3-expressing apoptotic cells induced a Th17 response, revealing a GPA-specific mechanism of immune polarization. Accordingly, circulating [CD4.sup.+] T cells from GPA patients had a skewed distribution of Th9/Th2/Th17. These results reveal that PR3 disrupts immune silencing associated with clearance of apoptotic neutrophils and provide insight into how PR3 and PR3-targeting ANCAs promote GPA pathophysiology., Introduction Granulomatosis with polyangiitis (GPA) is a systemic autoimmune disease characterized by granulomatous inflammation and necrotizing vasculitis (1). GPA is associated with anti-neutrophil cytoplasmic antibodies (ANCAs) directed against the neutrophil- [...]

Apolipoprotein CIII (ApoCIII) represents a key regulator of plasma lipid metabolism and a recognized risk factor for atherosclerosis and cardiovascular diseases. Beyond the regulation of lipoprotein trafficking, ApoCIII is also involved in endothelial dysfunction and monocyte recruitment related to atherothrombosis. With tissue factor (TF) being the primary initiator of the blood coagulation cascade, we hypothesized that ApoCIII-treated monocytes could express it. Hence, human CD14+-monocytes and autologous neutrophils were incubated with ApoCIII and sera from human subjects containing previously measured ApoCIII amounts. By RT-qPCR and ELISA, CD14+-monocytes, but not neutrophils, were found to show increased mRNA expression and production of TNFα, IL-1β and IL-6 as well as TF mRNA once exposed to ultra-purified ApoCIII. By flow cytometry, CD14+-monocytes were found to rapidly express TF on their cell surface membrane when incubated with either ApoCIII or sera with known concentrations of ApoCIII. Finally, preincubation with specific ApoCIII-neutralizing antibodies significantly reduced the ability of most sera with known concentrations of ApoCIII to upregulate TF protein, other than partially inhibiting cytokine release, in CD14+-monocytes. In sum, herein we demonstrate that ApoCIII activates CD14+-monocytes to express TF. The data identify a potential mechanism which links circulating apolipoproteins with inflammation and atherothrombosis-related processes underlying cardiovascular risk. [ABSTRACT FROM AUTHOR]