EBI3 Research Articles

Molecular Characterization of Oxysterol Binding to the Epstein-Barr Virus-induced Gene 2 (GPR183)

Oxysterols are oxygenated cholesterol derivates that are emerging as a physiologically important group of molecules. Although they regulate a range of cellular processes, only few oxysterol-binding effector proteins have been identified, and the knowledge of their binding mode is limited. Recently, the family of G protein-coupled seven transmembrane-spanning receptors (7TM receptors) was added to this group. Specifically, the Epstein-Barr virus-induced gene 2 (EBI2 or GPR183) was shown to be activated by several oxysterols, most potently by 7α,25-dihydroxycholesterol (7α,25-OHC). Nothing is known about the binding mode, however. Using mutational analysis, we identify here four key residues for 7α,25-OHC binding: Arg-87 in TM-II (position II:20/2.60), Tyr-112 and Tyr-116 (positions III:09/3.33 and III:13/3.37) in TM-III, and Tyr-260 in TM-VI (position VI:16/6.51). Substituting these residues with Ala and/or Phe results in a severe decrease in agonist binding and receptor activation. Docking simulations suggest that Tyr-116 interacts with the 3β-OH group in the agonist, Tyr-260 with the 7α-OH group, and Arg-87, either directly or indirectly, with the 25-OH group, although nearby residues likely also contribute. In addition, Tyr-112 is involved in 7α,25-OHC binding but via hydrophobic interactions. Finally, we show that II:20/2.60 constitutes an important residue for ligand binding in receptors carrying a positively charged residue at this position. This group is dominated by lipid- and nucleotide-activated receptors, here exemplified by the CysLTs, P2Y12, and P2Y14. In conclusion, we present the first molecular characterization of oxysterol binding to a 7TM receptor and identify position II:20/2.60 as a generally important residue for ligand binding in certain 7TM receptors.

O028 The signaling properties of Interleukin-30 underline plasticity and cross-talk among the Interleukin-6 family of cytokines

Introduction The anti-inflammatory Interleukin (IL)-6/IL-12 cytokine family member IL-27 consists of the cytokine Interleukin-30 (IL-30, also referred to as IL-27p28) and the non-signaling α -receptor subunit Epstein-Barr virus induced gene 3 (EBI3). Antigen-presenting cells are the major cellular source of both proteins, and IL-27 has been shown to engage signaling via a heterodimer of the two transmembrane receptors WSX-1 and gp130. Besides this well-established function, several studies suggest that IL-30 has signaling properties on its own. Recently, IL-30 was shown to form a novel cytokine complex with the non-signaling membrane-bound IL-6 receptor α (IL-6R). Methods Since free, endogenous IL-30 is not efficiently secreted, we developed a strategy for bacterial expression, purification and renaturation of murine IL-30 (mIL-30) for in vitro and in vivo analysis. Furthermore, we designed a Hyper-cytokine, consisting of the extracellular/soluble part of the IL-6R fused via a peptide linker to IL-30, and expressed the IL-30-sIL-6R fusion protein in mammalian cells. Results We show that mIL-30 can induce STAT-dependent proliferation of Ba/F3-gp130 cells expressing murine or human IL-6R, indicating that in contrast to murine IL-6, murine IL-30 possesses no species specificity. Furthermore, we identified the two transmembrane proteins that function as the signal transducing receptors of the IL-30/IL-6R complex. IL-30 was also able to induce IL-30-trans-signaling using the soluble IL-6R (sIL-6R), a characteristic property that was initially described for IL-6 signaling via the sIL-6R. We further show how STAT phosphorylation and proliferation of Ba/F3-gp130 cells induced by IL-30-sIL-6R can be efficiently inhibited. Finally, mIL-30 but not IL-6, was able to induce STAT-dependent proliferation of Ba/F3-gp130 cells without the need of the p28- α receptors IL-6R and EBI3, albeit at higher concentrations of mIL-30 in comparison to IL-30-sIL-6R. Conclusion Our study enlarges the spectrum of IL-30-dependent receptor activation pathways and might have major implications for the biological role of Interleukin-30 in vivo .

Analytical strategies for characterization of oxysterol lipidomes: Liver X receptor ligands in plasma

Bile acids, bile alcohols, and hormonal steroids represent the ultimate biologically active products of cholesterol metabolism in vertebrates. However, intermediates in their formation, including oxysterols and cholestenoic acids, also possess known, e.g., as ligands to nuclear and G-protein-coupled receptors, and unknown regulatory activities. The potential diversity of molecules originating from the cholesterol structure is very broad and their abundance in biological materials ranges over several orders of magnitude. Here we describe the application of enzyme-assisted derivatization for sterol analysis (EADSA) in combination with liquid chromatography–electrospray ionization–mass spectrometry to define the oxysterol and cholestenoic acid metabolomes of human plasma. Quantitative profiling of adult plasma using EADSA leads to the detection of over 30 metabolites derived from cholesterol, some of which are ligands to the nuclear receptors LXR, FXR, and pregnane X receptor or the G-protein-coupled receptor Epstein–Barr virus-induced gene 2. The potential of the EADSA technique in screening for inborn errors of cholesterol metabolism and biosynthesis is demonstrated by the unique plasma profile of patients suffering from cerebrotendinous xanthomatosis. The analytical methods described are easily adapted to the analysis of other biological fluids, including cerebrospinal fluid, and also tissues, e.g., brain, in which nuclear and G-protein-coupled receptors may have important regulatory roles.

Oxysterols and their cellular effectors.

Oxysterols are oxidized 27-carbon cholesterol derivatives or by-products of cholesterol biosynthesis, with a spectrum of biologic activities. Several oxysterols have cytotoxic and pro-apoptotic activities, the ability to interfere with the lateral domain organization, and packing of membrane lipids. These properties may account for their suggested roles in the pathology of diseases such as atherosclerosis, age-onset macular degeneration and Alzheimer’s disease. Oxysterols also have the capacity to induce inflammatory responses and play roles in cell differentiation processes. The functions of oxysterols as intermediates in the synthesis of bile acids and steroid hormones, and as readily transportable forms of sterol, are well established. Furthermore, their actions as endogenous regulators of gene expression in lipid metabolism via liver X receptors and the Insig (insulin-induced gene) proteins have been investigated in detail. The cytoplasmic oxysterol-binding protein (OSBP) homologues form a group of oxysterol/cholesterol sensors that has recently attracted a lot of attention. However, their mode of action is, as yet, poorly understood. Retinoic acid receptor-related orphan receptors (ROR) α and γ, and Epstein-Barr virus induced gene 2 (EBI2) have been identified as novel oxysterol receptors, revealing new physiologic oxysterol effector mechanisms in development, metabolism, and immunity, and evoking enhanced interest in these compounds in the field of biomedicine.

Effects on apoptosis and cell cycle arrest contribute to the antitumor responses of interleukin-27 mediated by retrovirus in human pancreatic carcinoma cells

Interleukin (IL)-27, composed of p28 and Epstein-Barr virus-induced gene 3 (EBI3) subunits, has diverse functions in regulating immune systems. Human melanoma cells have been shown to express both IL-27 receptor subunits, and growth inhibition by IL-27 was detected. We investigated whether forced expression of the p28-linked EBI3 gene in human pancreatic carcinoma cells (AsPC1) by retroviral vector would produce IL-27-mediated antitumor effects and the related mechanisms. The data demonstrated that AsPC1 cells expressed both IL-27 receptor subunits, and tumor growth of AsPC1/IL-27 in mice was retarded compared with vector DNA-transduced tumors and survival of the mice was prolonged. Expression of cytokines such as interferon-γ, tumor necrosis factor-α and IL-1β in tumor specimens increased, while the secretion of IFN-γ and TNF-α from spleen cells of mice bearing IL-27-transfected tumors increased. Moreover, cell cycle arrest was induced in AsPC1/IL-27 inoculated mice with upregulated p21 expression and downregulated survivin expression. The appearance of apoptotic cells increased in tumor specimens of mice bearing IL-27-transfected tumors compared with the mice bearing DNA-transfected tumors by confirming the expression of apoptosis-related proteins and activated apoptotic pathways through detection of cleaved PARP. These results suggest that transfection of the IL-27 gene into human pancreatic carcinoma cells could produce antitumor effects invivo and induction of cell cycle arrest and apoptosis could be the mechanism of IL-27 action in tumor regression.

Interleukin-27 is a novel candidate diagnostic biomarker for bacterial infection in critically ill children

IntroductionDifferentiating between sterile inflammation and bacterial infection in critically ill patients with fever and other signs of the systemic inflammatory response syndrome (SIRS) remains a clinical challenge. The objective of our study was to mine an existing genome-wide expression database for the discovery of candidate diagnostic biomarkers to predict the presence of bacterial infection in critically ill children.MethodsGenome-wide expression data were compared between patients with SIRS having negative bacterial cultures (n = 21) and patients with sepsis having positive bacterial cultures (n = 60). Differentially expressed genes were subjected to a leave-one-out cross-validation (LOOCV) procedure to predict SIRS or sepsis classes. Serum concentrations of interleukin-27 (IL-27) and procalcitonin (PCT) were compared between 101 patients with SIRS and 130 patients with sepsis. All data represent the first 24 hours of meeting criteria for either SIRS or sepsis.ResultsTwo hundred twenty one gene probes were differentially regulated between patients with SIRS and patients with sepsis. The LOOCV procedure correctly predicted 86% of the SIRS and sepsis classes, and Epstein-Barr virus-induced gene 3 (EBI3) had the highest predictive strength. Computer-assisted image analyses of gene-expression mosaics were able to predict infection with a specificity of 90% and a positive predictive value of 94%. Because EBI3 is a subunit of the heterodimeric cytokine, IL-27, we tested the ability of serum IL-27 protein concentrations to predict infection. At a cut-point value of ≥5 ng/ml, serum IL-27 protein concentrations predicted infection with a specificity and a positive predictive value of >90%, and the overall performance of IL-27 was generally better than that of PCT. A decision tree combining IL-27 and PCT improved overall predictive capacity compared with that of either biomarker alone.ConclusionsGenome-wide expression analysis has provided the foundation for the identification of IL-27 as a novel candidate diagnostic biomarker for predicting bacterial infection in critically ill children. Additional studies will be required to test further the diagnostic performance of IL-27.The microarray data reported in this article have been deposited in the Gene Expression Omnibus under accession number GSE4607.

Regulatory T cells inhibit acute IFN-γ synthesis without blocking T-helper cell type 1 (Th1) differentiation via a compartmentalized requirement for IL-10

CD4(+)CD25(+)Forkhead box P3 (Foxp3)(+) regulatory T cells (Tregs) control immune responses to self and foreign antigens in secondary lymphoid organs and at tissue sites of inflammation. Tregs can modify the function of many immune cells and have been proposed to block early proliferation, differentiation, and effector function. Acute ablation of Tregs has revealed rapid cytokine production immediately after Treg removal, suggesting that Tregs may regulate effector function acutely rather than regulating the programming for immune function. We developed in vitro and in vivo models that enabled the direct test of Treg regulation of T-helper cell type 1 (Th1) differentiation. CD28 signaling is known to abrogate Treg suppression of IL-2 secretion and proliferation, but our studies show that Treg suppression of IFN-γ during Th1 priming proceeds despite enhanced CD28 signaling. Importantly, during Th1 differentiation, Tregs inhibited early IFN-γ transcription without disrupting expression of Th1-specific T-box transcription factor (Tbet) and Th1 programming. Acute shutoff of effector cytokine production by Tregs was selective for IFN-γ but not TNF-α and was independent of TGF-β and Epstein-Barr virus-induced gene 3. In vivo, Tregs potently controlled CD4 IFN-γ and CD4 effector cell expansion in the lymph node (four- to fivefold reduction) but not Th1 programming, independent of IL-10. Tregs additionally reduced CD4 IFN-γ in the inflamed dermis (twofold reduction) dependent on their production of IL-10. We propose a model for Treg inhibition of effector function based on acute cytokine regulation. Interestingly, Tregs used different regulatory mechanisms to regulate IFN-γ (IL-10-dependent or -independent) subject to the target T-cell stage of activation and its tissue location.

Decreased Expression of EBI3 and Foxp3 in CD4+CD25+ Regulatory T Cells in Murine Experimental Allergic Rhinitis

Background: Epstein-Barr virus-induced gene 3 (EBI3) is a widely expressed interleukin-12-related protein that plays a critical role in the regulation of effector T cells and inflammatory responses. Methods: Allergic rhinitis (AR) was induced in mice by both intraperitoneal injection and intranasal administration of ovalbumin. By using immunohistochemical techniques, we investigated EBI3 expression in mouse spleens. The expressions of EBI3 and forkhead transcription factor 3 (Foxp3) in CD4+CD25+ regulatory T (T_reg) cells isolated from spleens were assessed by flow cytometry. RNA extraction and RT-PCR were used to measure EBI3 and Foxp3 mRNA expression. Results: EBI3 and Foxp3 were expressed mainly in the white pulp of the spleens. Flow cytometry analysis showed that EBI3 and Foxp3 coexpressed in mouse CD4+CD25+ T_reg cells. Furthermore, RT-PCR and flow cytometry analysis showed that expression of both Foxp3 and EBI3 was reduced in CD4+CD25+ T_reg cells in an AR mouse model compared with controls, but there was no difference in the frequency of CD4+CD25+ T_reg cells. Conclusions: The deficiency in CD4+CD25+ T_reg cell suppressive activity in AR is associated with the molecular mediators EBI3 and Foxp3.

Cell Therapy With Autologous Tolerogenic Dendritic Cells Induces Allograft Tolerance Through Interferon-Gamma and Epstein-Barr Virus-Induced Gene 3

Innovative therapeutic strategies are needed to diminish the impact of harmful immunosuppression in transplantation. Dendritic cell (DC)-based therapy is a promising approach for induction of antigen-specific tolerance. Using a heart allograft model in rats, we analyzed the immunoregulatory mechanisms by which injection of autologous tolerogenic DCs (ATDCs) plus suboptimal immunosuppression promotes indefinite graft survival. Surprisingly, we determined that Interferon-gamma (IFNG), a cytokine expected to be propathogenic, was threefold increased in the spleen of tolerant rats. Importantly, its blockade led to allograft rejection [Mean Survival Time (MST) = 25.6 ± 4 days], showing that IFNG plays a critical role in immunoregulatory mechanisms triggered by ATDCs. IFNG was expressed by TCRαβ(+) CD3(+) CD4(-) CD8(-) NKRP1(-) cells (double negative T cells, DNT), which accumulated in the spleen of tolerant rats. Interestingly, ATDCs specifically induced IFNG production by DNT cells. ATDCs expressed the cytokinic chain Epstein-Barr virus-induced gene 3 (EBI3), an IL-12 family member. EBI3 blockade or knock-down through siRNA completely abolished IFNG expression in DNT cells. Finally, EBI3 blockade in vivo led to allograft rejection (MST = 36.8 ± 19.7 days), demonstrating for the first time a role for EBI3 in transplantation tolerance. Taken together our results have important implications in the rationalization of DC-based therapy in transplantation as well as in the patient immunomonitoring follow-up.

IL-27 Inhibits Hyperglycemia and Pancreatic Islet Inflammation Induced by Streptozotocin in Mice

Inflammation driven by immune cells and pro-inflammatory cytokines is implicated in pancreatic β-cell injury, leading to the development of diabetes mellitus. IL-27, a cytokine consisting of IL-27p28 and Epstein-Barr virus-induced gene 3 (EBI3), binds a membrane-bound heterodimeric receptor consisting of the IL-27 receptor α chain (WSX-1) and gp130. IL-27 has anti-inflammatory properties that regulate T-cell polarization and cytokine production. We evaluated blood glucose and islet proinsulin concentrations, inflammatory cell infiltration in islets, and expression of IL-1β mRNA in pancreas in wild-type (WT), EBI3(-/-), and WSX-1(-/-) mice treated with streptozotocin (STZ). Hyperglycemia was augmented in EBI3(-/-) and WSX-1(-/-) mice compared with WT mice. Islet proinsulin levels after STZ treatment were lower in EBI3(-/-) and WSX-1(-/-) mice than in WT mice. The infiltration of islets by F4/80(+)CD11c(-)7/4(-) macrophages, CD4(+) T cells, and CD8(+) T cells was increased in EBI3(-/-) and WSX-1(-/-) mice compared with WT mice. The administration of recombinant IL-27, compared with control, decreased the blood glucose level, immune cell infiltration into islets, and IL-1β mRNA expression in the pancreas and increased islet proinsulin levels in WT and EBI3(-/-) mice. Thus, IL-27 inhibits STZ-induced hyperglycemia and pancreatic islet inflammation in mice and represents a potential novel therapeutic approach for β-cell protection in diabetes.

Epstein-Barr Virus-Induced Gene 3 (EBI3): A Novel Diagnosis Marker in Burkitt Lymphoma and Diffuse Large B-Cell Lymphoma

The distinction between Burkitt lymphoma (BL) and diffuse large B-cell lymphoma (DLBCL), two types of mature aggressive B-cell lymphomas that require distinct treatments, can be difficult because of forms showing features intermediate between DLBCL and BL (here called BL/DLBCL). They can be discriminated by the presence of c-myc translocations characteristic of BL. However, these are not exclusive of BL and when present in DLBCL are associated with lower survival. In this study, we show that Epstein-Barr virus-induced gene 3 (EBI3) is differentially expressed among BL and DLBCL. Analysis of gene expression data from 502 cases of aggressive mature B-cell lymphomas available on Gene Expression Omnibus and immunohistochemical analysis of 184 cases of BL, BL/DLBCL or DLBCL, showed that EBI3 was not expressed in EBV-positive or -negative BL cases, whereas it was expressed by over 30% of tumoral cells in nearly 80% of DLBCL cases, independently of their subtypes. In addition, we show that c-myc overexpression represses EBI3 expression, and that DLBCL or BL/DLBCL cases with c-myc translocations have lower expression of EBI3. Thus, EBI3 immunohistochemistry could be useful to discriminate BL from DLBCL, and to identify cases of BL/DLBCL or DLBCL with potential c-myc translocations.

Oxysterols direct immune cell migration via EBI2

Epstein-Barr virus-induced gene 2 (EBI2, also known as GPR183) is a G-protein-coupled receptor that is required for humoral immune responses; polymorphisms in the receptor have been associated with inflammatory autoimmune diseases. The natural ligand for EBI2 has been unknown. Here we describe the identification of 7α,25-dihydroxycholesterol (also called 7α,25-OHC or 5-cholesten-3β,7α,25-triol) as a potent and selective agonist of EBI2. Functional activation of human EBI2 by 7α,25-OHC and closely related oxysterols was verified by monitoring second messenger readouts and saturable, high-affinity radioligand binding. Furthermore, we find that 7α,25-OHC and closely related oxysterols act as chemoattractants for immune cells expressing EBI2 by directing cell migration in vitro and in vivo. A critical enzyme required for the generation of 7α,25-OHC is cholesterol 25-hydroxylase (CH25H). Similar to EBI2 receptor knockout mice, mice deficient in CH25H fail to position activated B cells within the spleen to the outer follicle and mount a reduced plasma cell response after an immune challenge. This demonstrates that CH25H generates EBI2 biological activity in vivo and indicates that the EBI2-oxysterol signalling pathway has an important role in the adaptive immune response.

Interleukin-27 signal pathways and tumor

Interleukin (IL)-27 is a new member of the IL-6/IL-12 family composed of p28 subunit and Epstein-Barr virus induced gene 3 (EBI3) subunit. Its receptor is composed of WSX-1 and gp130. It has dual properties including pro-inflammatory and anti-inflammatory function at different conditions. Studies have shown that IL-27 exerts its biological activities through stimulating JAK1/STAT1, JAK1/STAT3 signal pathways and regulating the production of Th1, Th17 as well as their related-cytokines. Furthermore, IL-27 can exert the role of anti-tumor activity by enhancing the effect of cytotoxic T cells and anti-angiogenesis. Key words: Interleukins; Signal transduction; Inflammation; Neoplasms

Macrophage IL-12p70 signaling prevents HSV-1-induced CNS autoimmunity triggered by autoaggressive CD4+ Tregs.

CD4(+)CD25(+)FoxP3(+) naturally occurring regulatory T cells (Tregs) maintain self-tolerance and function to suppress overly exuberant immune responses. However, it is unclear whether innate immune cells modulate Treg function. Here the authors examined the role of innate immunity in lymphomyeloid homeostasis. The involvement of B cells, dendritic cells (DCs), macrophages, natural killer (NK) cells, and T cells in central nervous system (CNS) demyelination in different strains of mice infected ocularly with herpes simplex virus type 1 (HSV-1) was investigated. The authors found that depletion of macrophages, but not DCs, B cells, NK cells, CD4(+) T cells, or CD8(+) T cells, induced CNS demyelination irrespective of virus or mouse strain. As with macrophage depletion, mice deficient in interleukin (IL)-12p35 or IL-12p40 showed CNS demyelination after HSV-1 infection, whereas demyelination was undetectable in HSV-1-infected, IL-23p19-deficient, or Epstein-Barr virus-induced gene 3-deficient mice. Demyelination could be rescued in macrophage-depleted mice after the injection of IL-12p70 DNA and in IL-12p35(-/-) or IL-12p40(-/-) mice after injection with IL-12p35 or IL-12p40 DNA or with recombinant viruses expressing IL-12p35 or IL-12p40. Using FoxP3-, CD4-, CD8-, or CD25-depletion and gene-deficient mouse approaches, the authors demonstrated that HSV-1-induced demyelination was blocked in the absence of CD4, CD25, or FoxP3 in macrophage-depleted mice. Flow cytometry showed an elevation of CD4(+)CD25(+)FoxP3(+) T cells in the spleens of infected macrophage-depleted mice, and adoptive transfer of CD4(+)CD25(+) T cells to infected macrophage-depleted severe combined immunodeficient mice induced CNS demyelination. The authors demonstrated that macrophage IL-12p70 signaling plays an important role in maintaining immune homeostasis in the CNS by preventing the development of autoaggressive CD4(+) Tregs.

Development of functionally active recombinant form of mouse IL-35 (57.11)

Abstract As a novel heterodimeric cytokine and one of the IL-12 family members, IL-35 is composed of IL-12p35 subunit and Epstein-Barr virus-induced gene 3 (EBI3) protein. IL-35 is known to play an essential role in immune regulation of the CD4+CD25+ Treg cells, alleviating inflammatory responses. We have developed the recombinant fusion construct of mouse IL-35 (mIL-35)-hIgG1 Fc (hFc), in which EBI3 and IL-12p35 are joined by a flexible linker of (Gly4Ser)3. The mIg k-chain leader sequence at the amino terminus also allows secretion of the fusion protein. The mIL-35 construct was stably expressed in HEK 293 cells, and culture supernatants of single clones were screened by ELISA using a combination of anti-hFc and anti-mEBI3 antibodies, among which the most positive clone 35-5 was selected and adapted in a serum-free culture system. Functional activity of the secreted mIL-35 from this clone was tested using the [3H]thymidine-based cell proliferation assay. When CD4+ T cells purified from TCR-transgenic DO11.10 mice were stimulated with a combination of syngeneic irradiated APCs and OVA peptide in the presence of the mIL-35 culture supernatants, the mIL-35 significantly suppressed CD4+ T cell proliferation. Furthermore, the mIL-35-mediated inhibition of CD4+ T cell proliferation was reversed by anti-mIL-35 antibody. Taken together, these results demonstrate that the recombinant mIL-35 is functionally active and can be a useful research tool to study T cell-based immune regulations.

Detectable expression of IL-35 in CD4+ T cells from peripheral blood of chronic Hepatitis B patients

Epstein-Barr virus-induced gene 3 (Ebi3) and the p35 subunit of IL-12 have been reported to form a heterodimeric cytokine, named IL-35, in human and mouse. In mice, IL-35 has been shown to be constitutively expressed by CD4(+)CD25(+)Foxp3(+) regulatory T cells (Tregs) and suggested to contribute to their suppressive activity. However, human CD4(+)CD25(+)Foxp3(+) Tregs do not constitutively express detectable amounts of IL-35 in both mRNA and protein levels. Circulating CD4(+)CD25(+) Treg frequency of chronic Hepatitis B patients significantly correlates with serum viral load. In this study, we investigated whether IL-35 expression could be detected in CD4(+) T cells from peripheral blood of chronic Hepatitis B patients. Using both RT-PCR and immunoprecipitation plus Western blot analysis, we demonstrated that IL-35 expression could be detected in the CD4(+) T cells from peripheral blood of Chronic Hepatitis B patients.

EBI3 deficiency leads to diminished T helper type 1 and increased T helper type 2 mediated airway inflammation

Despite extensive investigation of the signals required for development of T helper type 1 (Th1) and type 2 (Th2) immune responses, the mechanisms involved are still not well-defined. A critical role for Epstein-Barr virus-induced gene 3 (EBI3) in these responses has been proposed. EBI3, initially discovered as a transcriptionally activated gene in Epstein-Barr virus-infected B lymphocytes, codes for a subunit of the cytokine interleukin-27 (IL-27). While initial studies suggested that it had an important role in promoting Th1 responses, subsequent studies have revealed that EBI3 receptor signalling influences a variety of immune cell types and can inhibit both Th1 and Th2 responses. In the present study, we evaluated EBI3(-/-) mice for their ability to mount both Th1-mediated and Th2-mediated airway inflammatory responses. The EBI3(-/-) mice sensitized by exposure to inhaled ovalbumin plus a high dose of lipopolysaccharide, which normally results in Th1 responses in wild-type (WT) mice, instead developed Th2 type airway inflammation, with increased numbers of eosinophils. The EBI3(-/-) mice that were exposed to inhaled ovalbumin with a low dose of lipopolysaccharide, which induces Th2 responses in WT mice, showed a marked enhancement of these responses, with increased airway eosinophils, increased serum IgE levels and increased levels of Th2 cytokines (IL-4, IL-5 and IL-13) in culture supernatants of mediastinal lymph node cells. Increased production of Th2 cytokines was also seen when naive CD4(+) T cells from EBI3(-/-) mice were stimulated in vitro compared with cells from WT mice. These results provide the first evidence that EBI3 may play an inhibitory role in allergic asthma development.

Stimulatory Effect of LPS and Feedback Effect of PGE2 on IL-27 production

Interleukin (IL)-27 is a new member of the IL-6/IL-12 family, composed of two subunits, the Epstein-Barr virus-induced gene 3 (EBI3) and p28 chains (p28), and produced by activated monocytes and dendritic cells. IL-27 plays an important role in the regulation of differentiation of naive T helper cells and has diverse effects on innate immune cells. However, the pro-inflammatory mechanisms of IL-27 are still not well known. In this study, we investigated the effect of lipopolysaccharide (LPS) on the production of IL-27. We found that LPS-stimulated IL-27 production was in a dose-dependent and time-dependent manner in THP-1 cells. We have also shown that IL-27 induced PGE2 production and COX-2 gene expression at the level of mRNA as well as protein. Moreover, we found feed back effect of PGE2 on the production of IL-27 in THP-1 cells. The results suggest that PGE2 significantly inhibits LPS-induced IL-27 production, without affecting basal IL-27 expression. Further experiment suggests that PGE2 and LPS regulate IL-27 through NF-κB pathway. Our findings may have wide implication for IL-27 in inflammatory diseases.

IL-27 structural analysis demonstrates similarities with ciliary neurotrophic factor (CNTF) and leads to the identification of antagonistic variants

IL-27, consisting of the subunits IL-27p28 and Epstein-Barr virus-induced gene 3 (EBI3), is a heterodimeric cytokine belonging to the IL-6/IL-12 family of cytokines. IL-27p28 is a four-helical cytokine requiring association with the soluble receptor EBI3 to be efficiently secreted and functionally active. Computational and biological analyses of the IL-27 binding site 1 to its receptor revealed important structural proximities with the ciliary neurotrophic factor group of cytokines and highlighted the contribution of p28 Trp(97), as well as of EBI3 Phe(97), Asp(210), and Glu(159), as key residues in the interactions between both cytokine subunits. WSX-1 (IL-27R) and gp130 compose the IL-27 receptor-signaling complex, recruiting the STAT-1 and STAT-3 pathways. A study of IL-27 binding site 3 showed that Trp(197) was crucial for the cytokine's interaction with gp130, but that the mutated cytokine still recognized IL-27R on the cell surface. IL-27 exerts both pro- and anti-inflammatory functions, promoting proliferation and differentiation of Th1 and inhibiting Th17 differentiation. Our results led us to develop mutated forms of human and mouse IL-27 with antagonistic activities. Using an in vivo mouse model of concanavalin A-induced Th1-cell-mediated hepatitis, we showed that the murine IL-27 antagonist W195A decreased liver inflammation by downregulating the synthesis of CXCR3 ligands and several acute phase proteins. Together, these data suggest that IL-27 antagonism could be of interest in down-modulating acute IL-27-driven Th1-cell-mediated immune response.

E0102 Expression or secretion of IL-34 and IL-35 in the peripheral blood mononuclear cells from patients with dilated cardiomyopathy

ObjectiveThe aim of this study was to observe the level of interleukin (IL)-34 and IL-35 in peripheral blood mononuclear cells (PBMCs) with dilated cardiomyopathy (DCM), and explore the role of...