Siglec-1 Expression Research Articles

CD169+ macrophages are critical for osteoblast maintenance and promote intramembranous and endochondral ossification during bone repair

Osteal macrophages (osteomacs) contribute to bone homeostasis and regeneration. To further distinguish their functions from osteoclasts, which share many markers and growth factor requirements, we developed a rapid, enzyme-free osteomac enrichment protocol that permitted characterization of minimally manipulated osteomacs by flow cytometry. Osteomacs differ from osteoclasts in expression of Siglec1 (CD169). This distinction was confirmed using the CD169-diphtheria toxin (DT) receptor (DTR) knock-in model. DT treatment of naïve CD169-DTR mice resulted in selective and striking loss of osteomacs, whilst osteoclasts and trabecular bone area were unaffected. Consistent with a previously-reported trophic interaction, osteomac loss was accompanied by a concomitant and proportionately striking reduction in osteoblasts. The impact of CD169+ macrophage depletion was assessed in two models of bone injury that heal via either intramembranous (tibial injury) or endochondral (internally-plated femoral fracture model) ossification. In both models, CD169+ macrophage, including osteomac depletion compromised bone repair. Importantly, DT treatment in CD169-DTR mice did not affect osteoclast frequency in either model. In the femoral fracture model, the magnitude of callus formation correlated with the number of F4/80+ macrophages that persisted within the callus. Overall these observations provide compelling support that CD169+ osteomacs, independent of osteoclasts, provide vital pro-anabolic support to osteoblasts during both bone homeostasis and repair.

Immortalized porcine mesenchymal cells derived from nasal mucosa, lungs, lymph nodes, spleen and bone marrow retain their stemness properties and trigger the expression of siglec-1 in co-cultured blood monocytic cells.

Mesenchymal stromal cells have been isolated from different sources. They are multipotent cells capable of differentiating into many different cell types, including osteocytes, chondrocytes and adipocytes. They possess a therapeutic potential in the management of immune disorders and the repair of damaged tissues. Previous work in our laboratory showed an increase of the percentages of CD172a+, CD14+, CD163+, Siglec-1+, CD4+ and CD8+ hematopoietic cells, when co-cultured with immortalized mesenchymal cells derived from bone marrow. The present work aimed to demonstrate the stemness properties of SV40-immortalized mesenchymal cells derived from nasal mucosa, lungs, spleen, lymph nodes and red bone marrow and their immunomodulatory effect on blood monocytes. Mesenchymal cells from nasal mucosa, lungs, spleen, lymph nodes and red bone marrow were isolated and successfully immortalized using simian virus 40 large T antigen (SV40LT) and later, co-cultured with blood monocytes, in order to examine their differentiation stage (expression of Siglec-1). Flow cytometric analysis revealed that the five mesenchymal cell lines were positive for mesenchymal cell markers CD105, CD44, CD90 and CD29, but lacked the expression of myeloid cell markers CD16 and CD11b. Growth analysis of the cells demonstrated that bone marrow derived-mesenchymal cells proliferated faster compared with those derived from the other tissues. All five mesenchymal cell lines co-cultured with blood monocytes for 1, 2 and 7 days triggered the expression of siglec-1 in the monocytes. In contrast, no siglec-1+ cells were observed in monocyte cultures without mesenchymal cell lines. Mesenchymal cells isolated from nasal mucosa, lungs, spleen, lymph nodes and bone marrow were successfully immortalized and these cell lines retained their stemness properties and displayed immunomodulatory effects on blood monocytes.

Polymorphisms in SIGLEC1 contribute to susceptibility to pulmonary active tuberculosis possibly through the modulation of IL-1ß

Siglec-1/CD169 is a sialoadhesin expressed by macrophages thought to function in cell-to-cell interactions. In the lung, the expression of Siglec-1 is specific for alveolar macrophages and single nucleotide polymorphisms (SNPs) in SIGLEC1 have been recently associated with asthma severity.Taking in account the role of alveolar macrophages in the control of M. tuberculosis and the poor literature about the contribution of SIGLEC1 genetics in M. tuberculosis susceptibility and development of pulmonary active TB, selected SNPs in SIGLEC1 were analysed in a case/control cohort from a TB endemic area of Brazil Amazon.Our findings evidenced for the first time the novel association between SIGLEC1 rs3859664 SNP and active pulmonary TB. Intriguingly, carriers of the polymorphism produced less IL-1ß than non-carriers, suggesting the possible involvement of Siglec-1 signalling pathway with inflammasome complex.

Increased expression of Siglec-9 in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a common inflammatory lung disease. Sialic acid-binding immunoglobulin-type lectins 9 (Siglec-9) is predominantly expressed on innate immune cells and has been shown to exert regulatory effect on immune cells through glycan recognition. Soluble Siglec-9 (sSiglec-9), the extracellular region of Siglec-9, might fulfill its function partly by competitive inhibiting siglec-9 binding to its ligands; however, the role of Siglec-9 and sSiglec-9 in the pathogenesis COPD remain largely unknown. In this study, we showed that Siglec-9 expression in alveolar and peripheral blood neutrophil were increased in COPD patients by immunofluorescence and flow cytometry, respectively. Plasma levels of sSiglelc-9 were elevated in COPD patients by ELISA. In vitro, Siglec-9 expression and/or sSiglelc-9 levels were up-regulated by cigarette smoke extract (CSE), lipopolysaccharide (LPS), some cytokines, and dexamethasone (DEX). Recombinant sSiglce-9 increased oxidative burst in neutrophil and enhanced neutrophil chemotaxis toward IL-8 independent on CXCR1 and CXCR2 expression, but it did not affect neutrophil apoptosis or secretions of inflammatory cytokines. In conclusion, Siglec-9 was complementarily increased to induce a negative feedback loop to limit neutrophil activation in COPD, sSiglce-9 enhanced neutrophil ROS and chemotaxis toward IL-8 likely via competitively inhibiting ligands binding to Siglec-9.

Siglec-7 expression is reduced on a natural killer (NK) cell subset of obese humans

Obesity leads to an altered adipocytokine production negatively effecting the function of natural killer cells (NK cells), which are important effector cells of the innate immune system. NK cells provide a defence against tumour cells or virus infected cells and have different activating and inhibitory surface receptors to distinguish between normal and transformed cells. One group of the inhibitory receptors are the sialic acid-binding immunoglobulin-like lectins (Siglecs). The aim of this study was to compare the expression of Siglecs-7, -9 and -10 on NK cells from normal weight and obese subjects. Therefore peripheral blood mononuclear cells (PBMC) were isolated from 10 normal weight (BMI < 25 kg/m2) and 11 obese (BMI > 30 kg/m2) blood donors and analysed by flow cytometry. Moreover, the amount of sialic acid on NK cell was determined using a fluorescent labelled lectin that binds terminal sialic acids. Percentages of immune cells were not altered between normal weight and obese individuals. CD56bright NK cells from obese subjects had a reduced expression of Siglec-7 while the expression of Siglec-9 was not altered. The reduction of Siglec-7 expression on CD56bright NK cells might be a marker for their dysfunction. Moreover, Siglecs-7, -9 and -10 are not expressed on the NK cell lines NK-92 and NKL. When comparing the two NK cell subpopulations CD56bright and CD56dim, CD56bright NK cells had a higher amount of sialic acids on their surface compared to CD56dim NK cells regardless of body weight.

High maternal expression of SIGLEC1 on monocytes as a surrogate marker of a type I interferon signature is a risk factor for the development of autoimmune congenital heart block

ObjectivesAutoimmune congenital heart block (CHB) is associated with placental transcytosis of maternal autoantibodies directed against Ro/SS-A and La/SS-B. However, only about 2% of children born to mothers with the respective...

SIGLEC1 is a biomarker of disease activity and indicates extraglandular manifestation in primary Sjögren's syndrome

ObjectivesTo evaluate the interferon (IFN) biomarkers sialic acid binding Ig like lectin 1 (SIGLEC1, CD169) and IFN-γ-inducible protein-10 (IP-10) in patients with primary Sjögren's syndrome (pSS).Methods31 patients fulfilling the American-European...

OMIP‐034: Comprehensive immune phenotyping of human peripheral leukocytes by mass cytometry for monitoring immunomodulatory therapies

Keywords: mass cytometry; panel design; mass-response characteristic; human blood leukocytes; immune phenotyping; immune monitoring; autoimmunity; rheumatism; systemic lupus erythematosus (SLE); biomarker and clinical trial

Constitutively expressed Siglec-9 inhibits LPS-induced CCR7, but enhances IL-4-induced CD200R expression in human macrophages.

Siglecs recognize the sialic acid moiety and regulate various immune responses. In the present study, we compared the expression levels of Siglecs in human monocytes and macrophages using a quantitative real-time reverse transcription-polymerase chain reaction analysis. The differentiation of monocytes into macrophages by macrophage colony-stimulating factor or granulocyte macrophage colony-stimulating factor enhanced the expression of Siglec-7 and Siglec-9. The differentiated macrophages were stimulated by lipopolysaccharide (LPS) plus interferon (IFN)-γ or interleukin (IL)-4. The expression of Siglec-10 was enhanced by IL-4, whereas that of Siglec-7 was reduced by LPS plus IFN-γ. The expression of Siglec-9 was not affected by these stimuli. The knockdown of Siglec-9 enhanced the expression of CCR7 induced by the LPS or the LPS plus IFN-γ stimulation, and decreased the IL-4-induced expression of CD200R. These results suggest that Siglec-9 is one of the main Siglecs in human blood monocytes/macrophages and modulates innate immunity.

Induction of Siglec-1 by Endotoxin Tolerance Suppresses the Innate Immune Response by Promoting TGF-β1 Production

Sepsis is one of the leading causes of death worldwide. Although the prevailing theory for the sepsis syndrome is a condition of uncontrolled inflammation in response to infection, sepsis is increasingly being recognized as an immunosuppressive state known as endotoxin tolerance. We found sialylation of cell surface was significantly increased on LPS-induced tolerant cells; knockdown of Neu1 in macrophage cell line RAW 264.7 cells resulted in enhanced LPS-induced tolerance, whereas overexpression of Neu1 or treatment with sialidase abrogated LPS-induced tolerance, as defined by measuring TNF-α levels in the culture supernatants. We also found that the expression of Siglec-1 (a member of sialic acid-binding Ig (I)-like lectin family members, the predominant sialic acid-binding proteins on cell surface) was specifically up-regulated in endotoxin tolerant cells and the induction of Siglec-1 suppresses the innate immune response by promoting TGF-β1 production. The enhanced TGF-β1 production by Siglec-1 was significantly attenuated by spleen tyrosine kinase (Syk) inhibitor. Knockdown of siglec-1 in RAW 264.7 cells resulted in inhibiting the production of TGF-β1 by ubiquitin-dependent degradation of Syk. Mechanistically, Siglec-1 associates with adaptor protein DNAX-activation protein of 12 kDa (DAP12) and transduces a signal to Syk to control the production of TGF-β1 in endotoxin tolerance. Thus, Siglec-1 plays an important role in the development of endotoxin tolerance and targeted manipulation of this process could lead to a new therapeutic opportunity for patients with sepsis.

Type I IFN-Inducible Downregulation of MicroRNA-27a Feedback Inhibits Antiviral Innate Response by Upregulating Siglec1/TRIM27.

Upon recognition of viral components by pattern recognition receptors, including TLRs and retinoic acid-inducible gene I-like helicases, cells are activated to produce type I IFN, which plays key roles in host antiviral innate immune response. However, excessive IFN production may induce immune disorders, and the mechanisms responsible for the regulation of type I IFN production have attracted much attention. Furthermore, type I IFN activates the downstream IFN/JAK/STAT pathway to modulate expression of a set of genes against viral infection, but whether these genes can feedback regulate type I IFN production is poorly understood. In this study, by screening the microRNAs modulated by viral infection in macrophages, we identified that microRNA (miR)-27a was significantly downregulated via the IFN/JAK/STAT1/runt-related transcription factor 1 pathway. Inducible downregulation of miR-27a, in turn, negatively regulated vesicular stomatitis virus-triggered type I IFN production, thus promoting vesicular stomatitis virus replication in macrophages. Mechanistically, we found that miR-27a directly targeted sialic acid-binding Ig-like lectin (Siglec)1 and E3 ubiquitin ligase tripartite motif-containing protein 27 (TRIM27), both of which were previously verified as negative regulators of type I IFN production. Furthermore, we constructed "Sponge" transgenic mice against miR-27a expression and found that Siglec1 and TRIM27 expression were elevated whereas type I IFN production was inhibited and viral replication was aggregated in vivo. Therefore, type I IFN-induced downregulation of miR-27a can upregulate Siglec1 and TRIM27 expression, feedback inhibiting type I IFN production in antiviral innate response. Our study outlines a new negative way to feedback regulate type I IFN production.

Siglec-1-positive plasmacytoid dendritic cells (pDCs) in human peripheral blood: A semi-mature and myeloid-like subset imbalanced during protective and autoimmune responses

Plasmacytoid dendritic cells (pDCs) play a central role in the pathogenesis of systemic lupus erythematosus (SLE) as IFN-α producers and promoters of T-cell activation or tolerance. Here, we demonstrated by flow-cytometry and confocal microscopy that Siglec-1, a molecule involved in the regulation of adaptive immunoresponses, is expressed in a subset of semi-mature, myeloid-like pDCs in human blood. These pDCs express lower BDCA-2 and CD123 and higher HLA-DR and CD11c than Siglec-1-negative pDCs and do not produce IFN-α via TLR7/TLR9 engagement. In vitro, Siglec-1 expression was induced in Siglec-1-negative pDCs by influenza virus. Proportions of Siglec-1-positive/Siglec-1-negative pDCs were higher in SLE than in healthy controls and correlated with disease activity. Healthy donors immunized with yellow fever vaccine YFV-17D displayed different kinetics of the two pDC subsets during protective immune response. PDCs can be subdivided into two subsets according to Siglec-1 expression. These subsets may play specific roles in (auto)immune responses.

Erythropoietin Resistant Anemia Following Burn Trauma Is in Part Due to Defective Terminal Maturation of Orthochromatic Erythroblasts Influenced By Erythroblast Island Macrophages

Introduction: Erythropoietin resistant anemia persists for at least six months in patients discharged from intensive care unit (ICU) without any preexisting hematological disorders. Patients with greater than 10% total body surface area burn become anemic and are refractory to erythropoietin (Epo). Endogenous Epo is critical for the survival, proliferation and differentiation of erythroid progenitors during early-stage erythropoiesis. Erythropoiesis starts with the hematopoietic stem cell commitment to the erythroid lineage, and the newly developing erythroblasts are then nurtured in the erythroblastic islands (EBI), which support enucleating erythroblasts through adhesive interactions during terminal maturation. Our earlier reports in scald burn model indicate a myeloid bias following burn injury dictating bone marrow granulocyte monocyte progenitor versus megakaryocyte erythrocyte progenitors suggesting that Epo independent defects in CFU-E generation starts at the commitment stage. However, we found that Epo dependent proliferation remained intact in burn patient PBMC derived cultures, which was followed up to late erythroblast stage. Here we inquired whether erythroblast maturation stage is affected by burn injury, if so what phenotype of EBI macrophage contributes to the Epo resistant anemia in burn injury?Methods: To this end, four patients (2F and 2M), 40±7 years of age and 49.9±6.6%, TBSA burn were studied with consent and IRB approval. Blood samples collected twice at 7-10 days and 29-31 days post burn were analyzed. Age matched healthy volunteers served as controls (C). RBCs were generated ex vivo from burn patients' peripheral blood mononuclear compartment (PBMC) derived multi potent progenitors (MPPs) cultured with growth factors and autologous plasma. As it is difficult to obtain bone marrow from burn patients, parallel investigations were done in our mouse model of scald burn (15% TBSA) which causes Epo resistant anemia. To this end, bilateral femurs were harvested on post burn days (PBD) 3, 7, 14, 21 and total bone marrow erythroblasts and macrophages were investigated for ER-HR3, Siglec-1 and Vcam-1 expression. Erythroblast phenotype was characterized by flow cytometry, and validated by a pathologist.Results: We observed a defect in enucleation of orthochromatic erythroblasts (OrthoE) characterized by a significant 4-fold lower reticulocyte (CD235a+ CD71+/- Syto16-) to OrthoE (CD235a+ CD71+/- Syto16+) ratio (R/O) (P<0.05) post burn in patients compared to controls (Figure 1). In mice, peripheral hemoglobin, hematocrit and red blood cell counts were significantly lower from PBD 7 through PBD 21. In line with burn patient data, we observed similar impairment in enucleation of OrthoEs characterized by significantly lower reticulocyte (CD71+ Ter119+ Syto 16-) to OrthoE (CD71+ Ter119+ Syto 16+) ratio (R/O ratio) in the bone marrow of the burn versus control mice [2 fold lower R/O ratio from PBD 3 through PBD21 (P<0.05)]. We then investigated from both a macrophage and erythroblast perspective to understand the stage specific role of associated adhesion molecules. The mean fluorescence intensities (MFIs) of cell surface expressions of Siglec-1, and ER-HR3 were significantly decreased on F4/80+ macrophages from PBD 7 through PBD 21, (Figure 2) while changes in Vcam-1 was significantly low only on PBD 7. From the erythroblast perspective, only OrthoE expressed high intensities of macrophage adhesion molecules (Siglec1, Vcam-1 and ER-HR3) and not reticulocytes (Figure 3). However, the MFI of Siglec-1, Vcam-1 and ER-HR3 expression was significantly reduced on PBD 7, both in OrthoE and macrophages, indicating the essential role of these markers in enucleation.Conclusion: Our data demonstrate defective erythroblast maturation following burn, and identify potential mediators of this process. These findings provide a framework for further investigations to determine the mechanistic basis of erythropoietin resistant anemia in burn patients. [Display omitted] [Display omitted] [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Phenotypic and Functional Characterization of Monoclonal Antibodies with Specificity for Rhesus Macaque CD200, CD200R and Mincle.

Lectin-like molecules and their receptors are cell surface molecules that have been shown to play a role in either facilitating infection or serving as transporters of HIV/SIV in vivo. The role of these lectin-like molecules in the pathogenesis of HIV/SIV infection continues to be defined. In efforts to gain further insight on the potential role of these lectin-like molecules, our laboratory generated monoclonal antibodies (mAb) against the human analogs of rhesus macaque CD200, CD200R and Mincle, since the rhesus macaques are accepted as the most reliable animal model to study human HIV infection. The characterization of the cell lineages from the blood and various tissues of rhesus macaques that express these lectin-like molecules are described herein. Among the mononuclear cells, the cells of the myeloid lineage of rhesus macaques are the predominant cell lineages that express readily detectable levels of CD200, CD200R and Mincle that is similar to the expression of Siglec-1 and Siglec-3 reported by our laboratory earlier. Subset analysis revealed that a higher frequency of the CD14+/CD16- subset from normal rhesus macaques express CD200, CD200R and Mincle. Differences in the frequencies and density of expression of these molecules by the gated population of CD14+ cells from various tissues are noted with PBMC and bone marrow expressing the highest and the mononuclear cells isolated from the colon and ileum expressing the lowest levels. While a significant frequency of pDCs and mDCs express Siglec-1/Siglec-3, a much lower frequency expresses CD200, CD200R and Mincle in PBMCs from rhesus macaques. The mAb against CD200 and CD200R but not Mincle appear to inhibit the infection of macrophage tropic SIV/SHIV in vitro. We conclude that these mAbs may have potential to be used as adjunctive therapeutic agents to control/inhibit SIV/HIV infection.

Siglec1 suppresses antiviral innate immune response by inducing TBK1 degradation via the ubiquitin ligase TRIM27.

Type I interferon (IFN) production plays pivotal roles in host antiviral innate immune responses, but an excessive production of type I IFN leads to the development of immunopathological conditions. Investigations on the regulatory mechanisms underlying host type I IFN production are currently of great interest. Here, we found that the expression of lectin family member Siglec1 was upregulated by viral infection in macrophages, which was dependent on the IFN/JAK/STAT1 signaling pathway. Siglec1 was found to negatively regulate viral infection-triggered type I IFN production. Mechanistically, Siglec1 associates with DAP12 to recruit and activate the scaffolding function of SHP2; SHP2 then recruits E3 ubiquitin ligase TRIM27, which induces TBK1 degradation via K48-linked ubiquitination at Lys251 and Lys372. Therefore, viral infection-induced upregulation of Siglec1 feedback loop inhibits type I IFN production and suppresses antiviral innate immune responses. Our study outlines a novel mechanism of negative regulation of type I IFN production, which may help virus to escape immune elimination.

HIV-1 immune activation induces Siglec-1 expression and enhances viral trans-infection in blood and tissue myeloid cells.

BackgroundMyeloid cells are key players in the recognition and response of the host against invading viruses. Paradoxically, upon HIV-1 infection, myeloid cells might also promote viral pathogenesis through trans-infection, a mechanism that promotes HIV-1 transmission to target cells via viral capture and storage. The receptor Siglec-1 (CD169) potently enhances HIV-1 trans-infection and is regulated by immune activating signals present throughout the course of HIV-1 infection, such as interferon α (IFNα).ResultsHere we show that IFNα-activated dendritic cells, monocytes and macrophages have an enhanced ability to capture and trans-infect HIV-1 via Siglec-1 recognition of viral membrane gangliosides. Monocytes from untreated HIV-1-infected individuals trans-infect HIV-1 via Siglec-1, but this capacity diminishes after effective antiretroviral treatment. Furthermore, Siglec-1 is expressed on myeloid cells residing in lymphoid tissues, where it can mediate viral trans-infection.ConclusionsSiglec-1 on myeloid cells could fuel novel CD4+ T-cell infections and contribute to HIV-1 dissemination in vivo.Electronic supplementary materialThe online version of this article (doi:10.1186/s12977-015-0160-x) contains supplementary material, which is available to authorized users.

The proteasome inhibitior bortezomib depletes plasma cells and ameliorates clinical manifestations of refractory systemic lupus erythematosus

ObjectivesTo investigate whether bortezomib, a proteasome inhibitor approved for treatment of multiple myeloma, induces clinically relevant plasma cell (PC) depletion in patients with active, refractory systemic lupus erythematosus (SLE).MethodsTwelve patients...

SC-24 * IMPROVEMENT OF HUMAN MESENCHYMAL STEM CELL HOMING IN DELIVERY OF THERAPEUTIC AGENTS TO GLIOMA STEM CELL XENOGRAFTS

There is an urgent need to develop novel delivery methods for brain tumors. To this end, we have developed human bone marrow mesenchymal stem cells (MSCs) to overcome the problems associated with traditional therapeutic treatments. Compared with other cellular delivery systems, MSCs may be easily acquired from patients, can be readily expanded and engineered ex vivo, can be auto-transfused without fear of rejection, and are free of ethical concerns. Therefore, MSCs are the ideal cells for therapeutic clinical applications. Defining the process of homing of MSCs to tumors-which is largely unknown-is essential to improve their application in clinical medicine. We have recently exploited glioma stem cell (GSC) xenografts (GSCXs) as a pertinent clinical model of human gliomas, because unlike GBM cell lines, GSCXs recapitulate the histology of the tumor from which they are derived. After intravascular delivery some GSCXs attract MSCs, while others do not. We hypothesized that successful homing of MSCs to GSCXs requires chemoattraction, adhesion to the endothelial wall, and extravasation. Adhesion and extravasation are driven largely by lectin-carbohydrate interactions. Measurements of MSC and GSCX glycogene expression, glycan expression on cell surface proteins, and quantitative proteomics were performed. We compared the molecular landscapes of attracting vs. non-attracting GSCXs. Key findings were the shift from high-mannose type glycosylation on MSCs following exposure to chemoattractants and expression of SIGLEC9 by attractor GSCXs versus expression of SIGLEC8 in non-attractors. Attractor GSCXs displayed down-regulated galactosyltransferase activity, whereas non-attractors were enriched in transcripts related to mannosyltransferases. In attractor GSCXs, kallikrein 4, 13, 14, and 15 were upregulated. These serine proteases are likely to contribute to the modulation of the tumoral extracellular biochemical environment. Results from this project will lead to future engineering strategies to enhance engraftment of MSCs in gliomas, a concept that is likely to have great clinical benefit.

Abstract 3659: Engagement of myelomonocytic siglecs by tumor-associated ligands modulates innate immune responses to cancer

Abstract Sialic acids are dominant glycans on vertebrate cell surfaces, mediating roles as diverse as influenza infection, leukocyte trafficking and neural plasticity. It has long been known that malignant cells upregulate sialic acids, but few reasons for this have so far been elucidated. In apparently unrelated work, we have recently found that certain pathogenic bacteria coat themselves with sialic acids, thereby dampening innate immune responses, via engagement of inhibitory Siglecs (sialic acid binding Ig-like lectins). We therefore hypothesized that hypersialylated carcinoma cells might similarly engage Siglecs and modulate immune cell function. Confirming this hypothesis, we now have the first demonstration of the involvement of Siglecs in cancer progression in vivo. Siglec-9 is the most abundant inhibitory Siglec on human neutrophils and monocytes/macrophages. We first demonstrate that ligands for Siglec-9 are strongly upregulated in human carcinomas. We further provide evidence that ligands on carcinoma cells can inhibit neutrophil activation and killing of tumor cells by neutrophils. We then show that mice lacking Siglec-E (the murine functional equivalent of Siglec-9) have an increased immunosurveillance in autochthonous and transplantation models, which could be reversed by transgenic expression of Siglec-9 in myelomonocytic cells. Studies of later phases of tumor progression however showed that Siglec-E/-9 inhibits polarization of M2 macrophages and therefore impairs angiogenesis and tumor growth. In keeping with this dualistic role of myelomonocytic Siglecs during different phases of cancer progression, survival of non-small cell lung cancer patients with a polymorphism that reduced ligand binding to Siglec-9 had initially an improved survival, suggesting an increased immunosurveillance, but this effect was lost during longer followup. Our results identify inhibitory CD33-related myelomonocytic Siglecs as important players in cancer biology and as potential targets for immunomodulatory therapy. We show that hypersialylated carcinoma cells modulate the innate immune response by engaging Siglec-9 and inhibit either immunosurveillance or cancer-related inflammation. Our data also exemplify the dualistic role of innate immune cells and their receptors in cancer progression depending on the context and the microenvironment, i.e., growth control by immunosurveillance or growth support by cancer-related inflammation. Citation Format: Heinz Läubli, Oliver M. T. Pearce, Flavio Schwarz, Lingquan Deng, Michal Stanczak, Liwen Deng, Andrea Verhagen, Patrick Secrest, Chrissy Lusk, Ann G. Schwartz, Nissi Varki, Jack Bui, Ajit Varki. Engagement of myelomonocytic siglecs by tumor-associated ligands modulates innate immune responses to cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3659. doi:10.1158/1538-7445.AM2014-3659

A Type I Interferon Transcriptional Signature Precedes Autoimmunity in Children Genetically at Risk for Type 1 Diabetes

Diagnosis of the autoimmune disease type 1 diabetes (T1D) is preceded by the appearance of circulating autoantibodies to pancreatic islets. However, almost nothing is known about events leading to this islet autoimmunity. Previous epidemiological and genetic data have associated viral infections and antiviral type I interferon (IFN) immune response genes with T1D. Here, we first used DNA microarray analysis to identify IFN-β–inducible genes in vitro and then used this set of genes to define an IFN-inducible transcriptional signature in peripheral blood mononuclear cells from a group of active systemic lupus erythematosus patients (n = 25). Using this predefined set of 225 IFN signature genes, we investigated the expression of the signature in cohorts of healthy controls (n = 87), patients with T1D (n = 64), and a large longitudinal birth cohort of children genetically predisposed to T1D (n = 109; 454 microarrayed samples). Expression of the IFN signature was increased in genetically predisposed children before the development of autoantibodies (P = 0.0012) but not in patients with established T1D. Upregulation of IFN-inducible genes was transient, temporally associated with a recent history of upper respiratory tract infections (P = 0.0064), and marked by increased expression of SIGLEC-1 (CD169), a lectin-like receptor expressed on CD14+ monocytes. DNA variation in IFN-inducible genes altered T1D risk (P = 0.007), as exemplified by IFIH1, one of the genes in our IFN signature for which increased expression is a known risk factor for disease. These findings identify transient increased expression of type I IFN genes in preclinical diabetes as a risk factor for autoimmunity in children with a genetic predisposition to T1D.