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Langerhans cell histiocytosis (LCH) is a rare disease with an unknown etiology characterized by heterogeneous lesions containing CD207+CD1a+ cells that can arise in almost any tissue and cause significant morbidity and mortality. Precursors of pathological Langerhans cells have yet to be defined. Our aim was to identify circulating CD207+CD1a+ cells and their inducers in LCH. Expression of CD207 and CD1a in the blood myeloid compartment as well as thymic stromal lymphopoietin (TSLP) and transforming growth factor β (TGF-β) plasma levels were measured in 22 pediatric patients with active disease (AD) or nonactive disease (NAD). In patients with AD vs those with NAD,the myeloid compartment showed an increased CD11b (CD11bhigh plus CD11b+) fraction (39.7 ± 3.6 vs 18.6 ± 1.9),a higher percentage of circulating CD11bhighCD11c+CD207+ cells (44.5 ± 11.3 vs 3.2 ± 0.5),and the presence of CD11chighCD207+CD1a+ cells (25.0 ± 9.1 vs 2.3 ± 0.5). Blood CD207+CD1a+ cells were not observed in adult controls or umbilical cord. Increased TSLP and TGF-β levels were detected in patients with AD. Interestingly,plasma from patients with AD induces CD207 expression on CD14+ monocytes. We conclude that CD207+CD1a+ cells are circulating in patients with active LCH,and TSLP and TGF-β are potential drivers of Langerhans-like cells in vivo. View Publication

OBJECTIVE Atherosclerosis is a major cause of cardiovascular disease. Monocyte-endothelial cell interactions are partly mediated by expression of monocyte CX3CR1 and endothelial cell fractalkine (CX3CL1). Interrupting the interaction between this ligand-receptor pair should reduce monocyte binding to the endothelial wall and reduce atherosclerosis. We sought to reduce atherosclerosis by preventing monocyte-endothelial cell interactions through use of a long-acting CX3CR1 agonist. METHODS In this study,the chemokine domain of CX3CL1 was fused to the mouse Fc region to generate a long-acting soluble form of CX3CL1 suitable for chronic studies. CX3CL1-Fc or saline was injected twice a week (30 mg/kg) for 4 months into Ldlr knockout (KO) mice on an atherogenic western diet. RESULTS CX3CL1-Fc-treated Ldlr KO mice showed decreased en face aortic lesion surface area and reduced aortic root lesion size with decreased necrotic core area. Flow cytometry analyses of CX3CL1-Fc-treated aortic wall cell digests revealed a decrease in M1-like polarized macrophages and T cells. Moreover,CX3CL1-Fc administration reduced diet-induced atherosclerosis after switching from an atherogenic to a normal chow diet. In vitro monocyte adhesion studies revealed that CX3CL1-Fc treatment caused fewer monocytes to adhere to a human umbilical vein endothelial cell monolayer. Furthermore,a dorsal window chamber model demonstrated that CX3CL1-Fc treatment decreased in vivo leukocyte adhesion and rolling in live capillaries after short-term ischemia-reperfusion. CONCLUSION These results indicate that CX3CL1-Fc can inhibit monocyte/endothelial cell adhesion as well as reduce atherosclerosis. View Publication

P-selectin glycoprotein ligand-1 (PSGL-1) is a homodimeric transmembrane mucin on leukocytes. During inflammation,reversible interactions of PSGL-1 with selectins mediate leukocyte rolling on vascular surfaces. The transmembrane domain of PSGL-1 is required for dimerization,and the cytoplasmic domain propagates signals that activate β(2) integrins to slow rolling on integrin ligands. Leukocytes from knock-in ΔCD" mice express a truncated PSGL-1 that lacks the cytoplasmic domain. Unexpectedly� View Publication

The present study shows that alumina nanotopography affects monocyte/macrophage behavior. Human mononuclear cells cultured on alumina membranes with pore diameters of 20 and 200 nm were evaluated in terms of cell adhesion,viability,morphology,and release of proinflammatory cytokines. After 24 hours,cell adhesion was assessed by means of light microscopy and cell viability by measuring LDH release. The inflammatory response was evaluated by quantifying interleukin-1β and tumour necrosis factor-α. Finally,scanning electron microscopy was used to study cell morphology. Results showed pronounced differences in cell number,morphology,and cytokine release depending on the nanoporosity. Few but highly activated cells were found on the 200 nm porous alumina,while relatively larger number of cells were found on the 20 nm porous surface. However,despite their larger number,the cells adhering on the 20 nm surface exhibited reduced pro-inflammatory activity. The data of this paper implies that nanotopography could be exploited for controlling the inflammatory response to implants. View Publication

Polymorphonuclear neutrophils (PMNs) are critical for the formation,maintenance,and resolution of bacterial abscesses. However,the mechanisms that regulate PMN survival and proliferation during the evolution of an abscess are not well defined. Using a mouse model of Staphylococcus aureus abscess formation within a cutaneous wound,combined with real-time imaging of genetically tagged PMNs,we observed that a high bacterial burden elicited a sustained mobilization of PMNs from the bone marrow to the infected wound,where their lifespan was markedly extended. A continuous rise in wound PMN number,which was not accounted for by trafficking from the bone marrow or by prolonged survival,was correlated with the homing of c-kit(+)-progenitor cells from the blood to the wound,where they proliferated and formed mature PMNs. Furthermore,by blocking their recruitment with an antibody to c-kit,which severely limited the proliferation of mature PMNs in the wound and shortened mouse survival,we confirmed that progenitor cells are not only important contributors to PMN expansion in the wound,but are also functionally important for immune protection. We conclude that the abscess environment provides a niche capable of regulating PMN survival and local proliferation of bone marrow-derived c-kit(+)-progenitor cells. View Publication

Granulocyte colony-stimulating factor (G-CSF),the prototypical mobilizing cytokine,induces hematopoietic stem and progenitor cell (HSPC) mobilization from the bone marrow in a cell-nonautonomous fashion. This process is mediated,in part,through suppression of osteoblasts and disruption of CXCR4/CXCL12 signaling. The cellular targets of G-CSF that initiate the mobilization cascade have not been identified. We use mixed G-CSF receptor (G-CSFR)-deficient bone marrow chimeras to show that G-CSF-induced mobilization of HSPCs correlates poorly with the number of wild-type neutrophils. We generated transgenic mice in which expression of the G-CSFR is restricted to cells of the monocytic lineage. G-CSF-induced HSPC mobilization,osteoblast suppression,and inhibition of CXCL12 expression in the bone marrow of these transgenic mice are intact,demonstrating that G-CSFR signals in monocytic cells are sufficient to induce HSPC mobilization. Moreover,G-CSF treatment of wild-type mice is associated with marked loss of monocytic cells in the bone marrow. Finally,we show that bone marrow macrophages produce factors that support the growth and/or survival of osteoblasts in vitro. Together,these data suggest a model in which G-CSFR signals in bone marrow monocytic cells inhibit the production of trophic factors required for osteoblast lineage cell maintenance,ultimately leading to HSPC mobilization. View Publication

Dendritic cells (DCs) are a heterogeneous population of professional antigen-presenting cells and are key cells of the immune system,acquiring different phenotypes in accordance with their localization during the immune response. A subset of inflammatory DCs is derived from circulating monocytes (Mo) and has a key role in inflammation and infection. The pathways controlling Mo-DC differentiation are not fully understood. Our objective was to investigate the possible role of nicotinamide adenine dinucleotide phosphate reduced form oxidases (NOXs) in Mo-DC differentiation. In this study,we revealed that Mo-DC differentiation was inhibited by NOX inhibitors and reactive oxygen species scavengers. We show that the Mo-DC differentiation was dependent on p22phox,and not on gp91phox/NOX2,as shown by the reduced Mo-DC differentiation observed in chronic granulomatous disease patients lacking p22phox. Moreover,we revealed that NOX5 expression was strongly increased during Mo-DC differentiation,but not during Mo-macrophage differentiation. NOX5 was expressed in circulating myeloid DC,and at a lower level in plasmacytoid DC. Interestingly,NOX5 was localized at the outer membrane of the mitochondria and interacted with p22phox in Mo-DC. Selective inhibitors and small interfering RNAs for NOX5 indicated that NOX5 controlled Mo-DC differentiation by regulating the JAK/STAT/MAPK and NFκB pathways. These data demonstrate that the NOX5-p22phox complex drives Mo-DC differentiation,and thus could be critical for immunity and inflammation. View Publication

Combined analyses of gene networks and DNA sequence variation can provide new insights into the aetiology of common diseases that may not be apparent from genome-wide association studies alone. Recent advances in rat genomics are facilitating systems-genetics approaches. Here we report the use of integrated genome-wide approaches across seven rat tissues to identify gene networks and the loci underlying their regulation. We defined an interferon regulatory factor 7 (IRF7)-driven inflammatory network (IDIN) enriched for viral response genes,which represents a molecular biomarker for macrophages and which was regulated in multiple tissues by a locus on rat chromosome 15q25. We show that Epstein-Barr virus induced gene 2 (Ebi2,also known as Gpr183),which lies at this locus and controls B lymphocyte migration,is expressed in macrophages and regulates the IDIN. The human orthologous locus on chromosome 13q32 controlled the human equivalent of the IDIN,which was conserved in monocytes. IDIN genes were more likely to associate with susceptibility to type 1 diabetes (T1D)-a macrophage-associated autoimmune disease-than randomly selected immune response genes (P = 8.85 × 10(-6)). The human locus controlling the IDIN was associated with the risk of T1D at single nucleotide polymorphism rs9585056 (P = 7.0 × 10(-10); odds ratio,1.15),which was one of five single nucleotide polymorphisms in this region associated with EBI2 (GPR183) expression. These data implicate IRF7 network genes and their regulatory locus in the pathogenesis of T1D. View Publication

Pulmonary bacterial infections are a leading cause of death. Since the introduction of antibiotics,multidrug-resistant Klebsiella pneumoniae became an escalating threat. Therefore,development of methods to augment antibacterial defense is warranted. Neutrophil recruitment is critical to clear bacteria,and neutrophil migration in the lung requires the production of ELR(+) CXC chemokines. Although lung-specific CXCL1/keratinocyte cell-derived chemokine (KC) transgene expression causes neutrophil-mediated clearance of K. pneumoniae,the mechanisms underlying KC-mediated host defense against K. pneumoniae have not been explored. In this study,we delineated the host defense functions of KC during pulmonary K. pneumoniae infection using KC(-/-) mice. Our findings demonstrate that KC is important for expression of CXCL2/MIP-2 and CXCL5/LPS-induced CXC chemokine,and activation of NF-κB and MAPKs in the lung. Furthermore,KC derived from both hematopoietic and resident cells contributes to host defense against K. pneumoniae. Neutrophil depletion in mice before K. pneumoniae infection reveals no differences in the production of MIP-2 and LPS-induced CXC chemokine or activation of NF-κB and MAPKs in the lung. Using murine bone marrow-derived and alveolar macrophages,we confirmed KC-mediated upregulation of MIP-2 and activation of NF-κB and MAPKs on K. pneumoniae infection. Moreover,neutralizing KC in bone marrow-derived macrophages before K. pneumoniae challenge decreases bacteria-induced production of KC and MIP-2,and activation of NF-κB and MAPKs. These findings reveal the importance of KC produced by hematopoietic and resident cells in regulating pulmonary host defense against a bacterial pathogen via the activation of transcription factors and MAPKs,as well as the expression of cell adhesion molecules and other neutrophil chemoattractants. View Publication

The recruitment of monocytes and their differentiation into macrophages at sites of inflammation are key events in determining the outcome of the inflammatory response and initiating the return to tissue homeostasis. To study monocyte trafficking and macrophage differentiation in vivo,we have generated a novel transgenic reporter mouse expressing a green fluorescent protein (GFP) under the control of the human CD68 promoter. CD68-GFP mice express high levels of GFP in both monocyte and embryo-derived tissue resident macrophages in adult animals. The human CD68 promoter drives GFP expression in all CD115(+) monocytes of adult blood,spleen,and bone marrow; we took advantage of this to directly compare the trafficking of bone marrow-derived CD68-GFP monocytes to that of CX3CR1(GFP) monocytes in vivo using a sterile zymosan peritonitis model. Unlike CX3CR1(GFP) monocytes,which downregulate GFP expression on differentiation into macrophages in this model,CD68-GFP monocytes retain high-level GFP expression for 72 hours after differentiation into macrophages,allowing continued cell tracking during resolution of inflammation. In summary,this novel CD68-GFP transgenic reporter mouse line represents a powerful resource for analyzing monocyte mobilization and monocyte trafficking as well as studying the fate of recruited monocytes in models of acute and chronic inflammation. View Publication

Macrophages are a source of both proinflammatory and restorative functions in damaged tissue through complex dynamic phenotypic changes. Here,we sought to determine whether monocyte-derived macrophages (MDMs) contribute to recovery after acute sterile brain injury. By profiling the transcriptional dynamics of MDMs in the murine brain after experimental intracerebral hemorrhage (ICH),we found robust phenotypic changes in the infiltrating MDMs over time and demonstrated that MDMs are essential for optimal hematoma clearance and neurological recovery. Next,we identified the mechanism by which the engulfment of erythrocytes with exposed phosphatidylserine directly modulated the phenotype of both murine and human MDMs. In mice,loss of receptor tyrosine kinases AXL and MERTK reduced efferocytosis of eryptotic erythrocytes and hematoma clearance,worsened neurological recovery,exacerbated iron deposition,and decreased alternative activation of macrophages after ICH. Patients with higher circulating soluble AXL had poor 1-year outcomes after ICH onset,suggesting that therapeutically augmenting efferocytosis may improve functional outcomes by both reducing tissue injury and promoting the development of reparative macrophage responses. Thus,our results identify the efferocytosis of eryptotic erythrocytes through AXL/MERTK as a critical mechanism modulating macrophage phenotype and contributing to recovery from ICH. View Publication