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Systematic inflammation has been reported to contribute to cancer progression through various mechanisms; however, the exact mechanism is still the subject of research. In this study, we evaluated the influence of systematic inflammation on lung metastasis, using a murine abdominal sepsis model, and assessed its relationship with pneumonia after curative esophagectomy in patients with esophageal cancer.We used a murine abdominal sepsis model given highly metastatic osteosarcoma, to reveal the mechanism of systematic inflammation and its potential for lung metastasis. The therapeutic effect of aspirin (ASA) in preventing distant metastasis was also investigated. Subsequently, we analyzed, retrospectively, the relationship between pneumonia and lung metastasis after esophagectomy in patients who underwent esophagectomy at Keio University between January, 2007 and October, 2020.Abdominal sepsis provoked lung injury in the acute phase. ASA inhibited the recruitment of neutrophils triggered by the lung injury, and it also suppressed lung metastasis. Our retrospective study revealed that lung metastasis was more frequent in patients with postoperative pneumonia.Postoperative acute lung injury is associated with a higher risk of lung metastasis. ASA may be a potential preoperative treatment for inhibiting lung metastasis by preventing the recruitment of neutrophils.

Classical dendritic cells (cDC) are professional antigen-presenting cells (APC) that regulate immunity and tolerance. Neutrophil-derived cells with properties of DCs (nAPC) are observed in human diseases and after culture of neutrophils with cytokines. Here we show that FcγR-mediated endocytosis of antibody-antigen complexes or an anti-FcγRIIIB-antigen conjugate converts neutrophils into nAPCs that, in contrast to those generated with cytokines alone, activate T cells to levels observed with cDCs and elicit CD8+ T cell-dependent anti-tumor immunity in mice. Single cell transcript analyses and validation studies implicate the transcription factor PU.1 in neutrophil to nAPC conversion. In humans, blood nAPC frequency in lupus patients correlates with disease. Moreover, anti-FcγRIIIB-antigen conjugate treatment induces nAPCs that can activate autologous T cells when using neutrophils from individuals with myeloid neoplasms that harbor neoantigens or those vaccinated against bacterial toxins. Thus, anti-FcγRIIIB-antigen conjugate-induced conversion of neutrophils to immunogenic nAPCs may represent a possible immunotherapy for cancer and infectious diseases., Neutrophils are versatile immune cells that may also serve as antigen-presenting cells (APC). Here the authors show that engaging FcγRs on neutrophils with immune complexes or an anti-FcγR-antigen conjugate induces neutrophil APC with comparable functions as classical dendritic cells, and with therapeutic potentials for cancer and infectious diseases.

It is widely appreciated that Fcγ receptors (FcγRs) regulate autoimmunity and end-organ damage, which are essential elements of systemic lupus erythematosus (SLE). FcγR polymorphisms, together with other genetic and environmental factors, dictate susceptibility to disease by altering the humoral response to lupus autoantigens as well as modifying the effector response of leukocytes responsible for end-organ damage. A balance of inhibitory and activating FcγRs on leukocyte subsets promotes immune complex clearance and may set the threshold for activation of cellular effector responses that potentially have deleterious effects on host tissue. In particular, FcγRIIB inhibits B cell reactivity to autoantigens and plays a central role in preserving peripheral immune tolerance. In this chapter, the structural and functional features of individual FcγR family members are outlined. The role of FcγRs in the initiation of autoantibody production, immune complex clearance, and SLE manifestations (such as nephritis) are discussed primarily in the context of murine models of disease as mice with genetically engineered modification of FcγRs expression have served as important tools in this area. Finally, a summary of the association of FcγR polymorphisms with susceptibility to SLE in humans is provided.

Group A Streptococcus (GAS) secretes deoxyribonucleases and evades neutrophil extracellular killing by degrading neutrophil extracellular traps (NETs). However, limited information is currently available on the interaction between GAS and NETs in the pathogenicity of GAS pharyngitis. In this study, we modified a mouse model of GAS pharyngitis and revealed an essential role for DNase in this model. After intranasal infection, the nasal mucosa was markedly damaged near the nasal cavity, at which GAS was surrounded by neutrophils. When neutrophils were depleted from mice, GAS colonization and damage to the nasal mucosa were significantly decreased. Furthermore, mice infected with deoxyribonuclease knockout GAS mutants (∆spd, ∆endA, and ∆sdaD2) survived significantly better than those infected with wild-type GAS. In addition, the supernatants of digested NETs enhanced GAS-induced cell death in vitro. Collectively, these results indicate that NET degradation products may contribute to the establishment of pharyngeal infection caused by GAS.

ObjectiveImmune complexes (ICs) play a critical role in the pathology of autoimmune diseases. The aim of this study was to generate and characterise a first-in-class anti-FcγRIIA antibody (Ab) VIB9600 (previously known as MEDI9600) that blocks IgG immune complex-mediated cellular activation for clinical development.MethodsVIB9600 was humanised and optimised from the IV.3 Ab. Binding affinity and specificity were determined by Biacore and ELISA. Confocal microscopy, Flow Cytometry-based assays and binding competition assays were used to assess the mode of action of the antibody. In vitro cell-based assays were used to demonstrate suppression of IC-mediated inflammatory responses. In vivo target suppression and efficacy was demonstrated in FcγRIIA-transgenic mice. Single-dose pharmacokinetic (PK)/pharmacodynamic study multiple dose Good Laboratory Practice (GLP) toxicity studies were conducted in non-human primates.ResultsWe generated a humanised effector-deficient anti-FcγRIIA antibody (VIB9600) that potently blocks autoantibody and IC-mediated proinflammatory responses. VIB9600 suppresses FcγRIIA activation by blocking ligand engagement and by internalising FcγRIIA from the cell surface. VIB9600 inhibits IC-induced type I interferons from plasmacytoid dendritic cells (involved in SLE), antineutrophil cytoplasmic antibody (ANCA)-induced production of reactive oxygen species by neutrophils (involved in ANCA-associated vasculitis) and IC-induced tumour necrosis factor α and interleukin-6 production (involved in rheumatoid arthritis). In FcγRIIA transgenic mice, VIB9600 suppressed antiplatelet antibody-induced thrombocytopaenia, acute anti-GBM Ab-induced nephritis and anticollagen Ab-induced arthritis. VIB9600 also exhibited favourable PK and safety profiles in cynomolgus monkey studies.ConclusionsVIB9600 is a specific humanised antibody antagonist of FcγRIIA with null effector function that warrants further clinical development for the treatment of IC-mediated diseases.

Rhabdomyolysis is a serious syndrome caused by skeletal muscle injury and the subsequent release of breakdown products from damaged muscle cells into systemic circulation. The muscle damage most often results from strenuous exercise, muscle hypoxia, medications, or drug abuse and can lead to life-threatening complications, such as acute kidney injury (AKI). Rhabdomyolysis and the AKI complication can also occur during crush syndrome, an emergency condition that commonly occurs in victims of natural disasters, such as earthquakes, and man-made disasters, such as wars and terrorism. Myoglobin released from damaged muscle is believed to trigger renal dysfunction in this form of AKI. Recently, macrophages were implicated in the disease pathogenesis of rhabdomyolysis-induced AKI, but the precise molecular mechanism remains unclear. In the present study, we show that macrophages released extracellular traps (ETs) comprising DNA fibers and granule proteins in a mouse model of rhabdomyolysis. Heme-activated platelets released from necrotic muscle cells during rhabdomyolysis enhanced the production of macrophage extracellular traps (METs) through increasing intracellular reactive oxygen species generation and histone citrullination. Here we report, for the first time to our knowledge, this unanticipated role for METs and platelets as a sensor of myoglobin-derived heme in rhabdomyolysis-induced AKI. This previously unknown mechanism might be targeted for treatment of the disease. Finally, we found a new therapeutic tool for prevention of AKI after rhabdomyolysis, which might rescue some sufferers of this pathology.

SUMMARY The interaction of the human FcγRIIA with immune complexes (ICs) promotes neutrophil activation and thus must be tightly controlled to avoid damage to healthy tissue. Here, we demonstrate that a fungal-derived soluble β-1,3/1,6-glucan binds to the glycosphingolipid long-chain lactosylceramide (LacCer) to reduce FcγRIIA-mediated recruitment to immobilized ICs under flow, a process requiring high-affinity FcγRIIA-immunoglobulin G (IgG) interactions. The inhibition requires Lyn phosphorylation of SHP-1 phosphatase and the FcγRIIA immunotyrosine-activating motif. β-glucan reduces the effective 2D affinity of FcγRIIA for IgG via Lyn and SHP-1 and, in vivo, inhibits FcγRIIA-mediated neutrophil recruitment to intravascular IgG deposited in the kidney glomeruli in a glycosphingolipid- and Lyn-dependent manner. In contrast, β-glucan did not affect FcγR functions that bypass FcγR affinity for IgG. In summary, we have identified a pathway for modulating the 2D affinity of FcγRIIA for ligand that relies on LacCer-Lyn-SHP-1-mediated inhibitory signaling triggered by β-glucan, a previously described activator of innate immunity., In brief Okubo et al. demonstrate that β-glucan binding to the glycosphingolipid lactosylceramide engages a Lyn kinase to SHP-1 phosphatase pathway that reduces FcγRIIA binding propensity for IgG, which suggests FcγRIIA affinity regulation by “inside-out” signaling. The β-glucan-lactosylceramide-Lyn axis prevents FcγRIIA-dependent neutrophil recruitment in vitro and to intravascular IgG deposits following glomerulonephritis., Graphical Abstract

Neutrophils are central players in the innate immune system. They generate neutrophil extracellular traps (NETs), which protect against invading pathogens but are also associated with the development of autoimmune and/or inflammatory diseases and thrombosis. Here, we report that lactoferrin, one of the components of NETs, translocated from the cytoplasm to the plasma membrane and markedly suppressed NETs release. Furthermore, exogenous lactoferrin shrunk the chromatin fibers found in released NETs, without affecting the generation of oxygen radicals, but this failed after chemical removal of the positive charge of lactoferrin, suggesting that charge-charge interactions between lactoferrin and NETs were required for this function. In a model of immune complex-induced NET formation in vivo, intravenous lactoferrin injection markedly reduced the extent of NET formation. These observations suggest that lactoferrin serves as an intrinsic inhibitor of NETs release into the circulation. Thus, lactoferrin may represent a therapeutic lead for controlling NETs release in autoimmune and/or inflammatory diseases., Highlights • We developed a real-time cell imaging system which can visualize neutrophil activation, DNA and cell membrane structures. • Lactoferrin serves as an intrinsic inhibitor of neutrophil extracellular traps (NETs) release into the circulation. • Lactoferrin may be a novel therapeutic target in pathological conditions related to NETs. Neutrophils generate neutrophil extracellular traps (NETs), which protect against invading pathogens but are also associated with the development of autoimmune and/or inflammatory diseases and thrombosis. Controlling NETs release is one of the promising therapeutic strategies for the treatment of these diseases. Lactoferrin is a multifunctional protein which is found mainly in human maternal milk, tears, and neutrophils granules and so on. We found that lactoferrin serves an endogenous inhibitor of NETs release into the circulation in inflammatory conditions. Thus, lactoferrin may represent a therapeutic lead for controlling NETs release in autoimmune and/or inflammatory diseases.

Vascular-deposited IgG immune complexes promote neutrophil recruitment, but how this process is regulated is still unclear. Here we show that the CD18 integrin Mac-1, in its bent state, interacts with the IgG receptor FcγRIIA in cis to reduce the affinity of FcγRIIA for IgG and inhibit FcγRIIA-mediated neutrophil recruitment under flow. The Mac-1 rs1143679 lupus-risk variant reverses Mac-1 inhibition of FcγRIIA, as does a Mac-1 ligand and a mutation in Mac-1’s ligand binding αI-domain. Sialylated complex glycans on FcγRIIA interact with the αI-domain via divalent cations, and this interaction is required for FcγRIIA inhibition by Mac-1. Human neutrophils deficient in CD18 integrins exhibit augmented FcγRIIA-dependent recruitment to IgG-coated endothelium. In mice, CD18 integrins on neutrophils dampen IgG-mediated neutrophil accumulation in the kidney. In summary, cis interaction between sialylated FcγRIIA and the αI-domain of Mac-1 alters the threshold for IgG-mediated neutrophil recruitment. A disruption of this interaction may increase neutrophil influx in autoimmune diseases., Deposited immune complexes (IC) promote neutrophil recruitment, but the fine tuning of this process is still unclear. Here the authors show that the cis interaction of the IC receptor, FcγRIIA and CD18 integrin, Mac-1, on the neutrophil surface modulates neutrophil adhesion, with FcγRIIA sialylation specifically implicated in this interaction.