Interleukin 27 limits autoimmune encephalomyelitis by suppressing the development of interleukin 17-producing T cells

Immunity to infection in IL-17-deficient mice and humans

Mice with defective IL-17 immunity display a broad vulnerability to various infectious agents at diverse mucocutaneous surfaces. In humans, the study of patients with various primary immunodeficiencies, including autosomal dominant hyper-IgE syndrome caused by dominant-negative STAT3 mutations and autosomal recessive autoimmune polyendocrinopathy syndrome type 1 caused by null mutations in AIRE, has suggested that IL-17A, IL-17F and/or IL-22 are essential for mucocutaneous immunity to Candida albicans. This hypothesis was confirmed by the identification of rare patients with chronic mucocutaneous candidiasis (CMC) due to autosomal recessive IL-17RA deficiency and autosomal dominant IL-17F deficiency. Heterozygosity for gain-of-function mutations in STAT1 in additional patients with CMC was recently shown to inhibit the development of IL-17 T cells. Although the infectious phenotype of patients with CMC and inborn errors of IL-17 immunity remains to be finely delineated, it appears that human IL-17A and IL-17F display redundancy for protective immunity in natural conditions that is not seen in their mouse orthologs in experimental conditions.

A polyglutamic acid motif confers IL-27 hydroxyapatite and bone-binding properties

The p28 subunit of the composite cytokine IL-27 comprises a polyglutamic acid domain, which is unique among type I cytokines. This domain is very similar to the acidic domain known to confer hydroxyapatite (HA)-binding properties and bone tropism to bone sialoprotein. We observed IL-27 binding to HA, in accordance with previous studies reporting successful p28 HA chromatography. The IL-27 polyglutamic acid domain is located in a flexible inter-α helix loop, and HA-bound IL-27 retained biological activity. Using IL-27 alanine mutants, we observed that the p28 polyglutamic acid domain confers HA- and bone-binding properties to IL-27 in vitro and bone tropism in vivo. Because IL-27 is a potent regulator of cells residing in endosteal bone marrow niches such as osteoclasts, T regulatory, memory T, plasma, and stem cells, this specific property could be beneficial for therapeutic applications. IL-27 has potent antitumoral and antiosteoclastogenic activities. It could therefore also be useful for therapies targeting hematologic cancer or solid tumors metastasis with bone tropism. Furthermore, these observations suggest that polyglutamic motifs could be grafted onto other type I cytokine inter-α helix loops to modify their pharmacological properties.

IL-27 activates Th1-mediated responses in imiquimod-induced psoriasis-like skin lesions

IL-27, a member of the IL-12 cytokine family, primes Th1 cell differentiation, whereas it suppresses Th17 cell development. We have previously reported that serum IL-27 levels are elevated in psoriatic patients and that IL-27 greatly induces in vitro production of Th1-type chemokines through STAT1 activation. In this study, to further investigate the in vivo role of IL-27 in the pathogenesis of psoriasis, we induced psoriasis-like inflammation on mouse back skin with topical application of imiquimod (IMQ), and continuously injected IL-27 or PBS subcutaneously. IMQ-treated skin showed an increase of IL-27 mRNA levels and the infiltration of IL-27-producing cells in the papillary dermis. The injection of IL-27 to the IMQ-treated skin exacerbated the disease compared with PBS injection. The IL-27 injection further augmented mRNA levels of IFN-γ, CXCL9, CXCL10, CXCL11, and TNF-α, without altering those of IL-17A, IL-17F, IL-22, and CCL20. Finally, IL-27 antagonism attenuated the upregulation of IFN-γ, CXCL9, CXCL10, CXCL11, and TNF-α mRNA levels, and induced clinical and histological improvement in the IMQ-treated skin. These results indicate that IL-27 would act in a proinflammatory manner, and thereby exacerbate the psoriasis-like skin inflammation induced by IMQ.

A novel role for IL-27 in mediating the survival of activated mouse CD4 T lymphocytes

IL-27, an IL-12 family cytokine, has pleiotropic functions in the differentiation and expansion of CD4(+) T cell subsets. In this study, we discovered a novel function of IL-27. CD4(+)CD45RB(high) T cells from mice deficient for the α-chain of IL-27 receptor failed to induce colitis in Rag(-/-) recipients, because of an inability of activated donor cells to survive. Interestingly, IL-27 was indispensable for the prevention of colitis by regulatory T cells, also because of a defect in long-term cell survival. IL-27 affected the survival of activated T lymphocytes, rather than promoting cell proliferation, by inhibiting Fas-mediated activation-induced T cell death, acting through the STAT3 signaling pathway. The addition of IL-27 during activation resulted in an increased cell number, which was correlated with decreased activation of both caspases 3 and 8. This prosurvival effect was attributed to downregulation of FasL and to the induction of the antiapoptotic protein cFLIP. Although activation induced cell death is an important mechanism for the maintenance of immunological homeostasis, protection of lymphocytes from excessive cell death is essential for effective immunity. Our data indicate that IL-27 has a crucial role in the inhibition of activation-induced cell death, thereby permitting Ag-driven T cell expansion.

Th1 and Th17 lymphocytes expressing CD161 are implicated in giant cell arteritis and polymyalgia rheumatica pathogenesis

OBJECTIVE

Giant cell arteritis (GCA) is the most frequently occurring vasculitis in elderly individuals, and its pathogenesis is not fully understood. The objective of this study was to decipher the role of the major CD4+ T cell subsets in GCA and its rheumatologic form, polymyalgia rheumatica (PMR).

METHODS

A prospective study of the phenotype and the function of major CD4+ T cell subsets (Th1, Th17, and Treg cells) was performed in 34 untreated patients with GCA or PMR, in comparison with 31 healthy control subjects and with the 27 treated patients who remained after the 7 others withdrew.

RESULTS

Compared with control subjects, patients with GCA and patients with PMR had a decreased frequency of Treg cells and Th1 cells, whereas the percentage of Th17 cells was significantly increased. Furthermore, an analysis of temporal artery biopsy specimens obtained from patients affected by GCA for whom biopsy results were positive demonstrated massive infiltration by Th17 and Th1 lymphocytes without any Treg cells. After glucocorticoid treatment, the percentages of circulating Th1 and Th17 cells decreased, whereas no change in the Treg cell frequency was observed. The frequency of CD161+CD4+ T cells, which are considered to be Th17 cell precursors, was similar in patients and control subjects. However, these cells highly infiltrated GCA temporal artery biopsy specimens, and their ability to produce interleukin-17 in vitro was significantly enhanced in patients with GCA and patients with PMR and was correlated with a decrease in the phosphorylated form of STAT-1.

CONCLUSION

This study is the first to demonstrate that the frequency of Treg cells is decreased in patients with GCA and patients with PMR, and that CD161+CD4+ T lymphocytes, differentiated into Th1 cells and Th17 cells, are involved in the pathogenesis of GCA and PMR.

Characterization of the interaction between astrocytes and encephalitogenic lymphocytes during the development of experimental autoimmune encephalitomyelitis (EAE) in mice

The nature of pathogenic mechanisms associated with the development of multiple sclerosis (MS) have long been debated. However, limited research was conducted to define the interplay between infiltrating lymphocytes and resident cells of the central nervous system (CNS). Data presented in this report describe a novel role for astrocyte-mediated alterations to myelin oligodendrocyte glycoprotein (MOG)(35-55) -specific lymphocyte responses, elicited during the development of experimental autoimmune encephalitomyelitis (EAE). In-vitro studies demonstrated that astrocytes inhibited the proliferation and interferon (IFN)-γ, interleukin (IL)-4, IL-17 and transforming growth factor (TGF)-β secretion levels of MOG(35-55) -specific lymphocytes, an effect that could be ameliorated by astrocyte IL-27 neutralization. However, when astrocytes were pretreated with IFN-γ, they could promote the proliferation and secretion levels of MOG(35-55) -specific lymphocytes, coinciding with apparent expression of major histocompatibility complex (MHC)-II on astrocytes themselves. Quantitative polymerase chain reaction (qPCR) demonstrated that production of IL-27 in the spinal cord was at its highest during the initial phases. Conversely, production of IFN-γ in the spinal cord was highest during the peak phase. Quantitative analysis of MHC-II expression in the spinal cord showed that there was a positive correlation between MHC-II expression and IFN-γ production. In addition, astrocyte MHC-II expression levels correlated positively with IFN-γ production in the spinal cord. These findings suggested that astrocytes might function as both inhibitors and promoters of EAE. Astrocytes prevented MOG(35-55) -specific lymphocyte function by secreting IL-27 during the initial phases of EAE. Then, in the presence of higher IFN-γ levels in the spinal cord, astrocytes were converted into antigen-presenting cells. This conversion might promote the progression of pathological damage and result in a peak of EAE severity.

Lack of association between IL27 gene variants and type 1 diabetes susceptibility

BACKGROUND

Recently, a new subpopulation of T cells, the Th17 subset, has been implicated in autoimmune diseases. Its development is influenced by IL-27, expressed in macrophages or dendritic cells. IL-27 blockage delays the onset of diabetes in non obese diabetes mouse, but its role in type 1 diabetes (T1D) in human has not been reported yet. The aim of this study was identify variants in the entire coding regions of IL-27 gene, including the 5' proximal region, and their possible association with the disease.

METHODS

Those regions were amplified by polymerase chain reaction followed by automatic sequencing and restriction fragments length polymorphisms. The cohort involved 614 individuals - 318 patients with T1D (19.6 ± 11.2 y, 129M/189F) and 296 healthy control subjects (30.3 ± 13.2 y, 131M/165F).

RESULTS

We identified eight allelic variants in the 5' proximal and coding regions of IL-27 gene, including two new variants: the c.-324 C>T in the 5' proximal region and the c.521 G>C in exon 5. None of these variants compromised transcription factor binding sites or the protein structure. The frequency of the alleles and genotypes of IL-27 variants did not differ between T1D patients and controls. There was no association between IL27 variants with gender, ethnicity, age at diagnosis of diabetes or presence of pancreatic and extrapancreatic autoantibodies.

CONCLUSION

Our findings suggest that allelic variants in IL27 are not associated with susceptibility to T1D in a Brazilian population.

Interferon regulatory factor 3 deficiency leads to interleukin-17-mediated liver ischemia-reperfusion injury

Interferon regulatory factor 3 (IRF3) is an important transcription factor in Toll-like receptor 4 (TLR4) signaling, a pathway that is known to play a critical role in liver ischemia-reperfusion injury. In order to decipher the involvement of IRF3 in this setting, we first compared the intensity of hepatic lesions in IRF3-deficient versus wildtype mice. We found increased levels of blood transaminases, enhanced liver necrosis, and more pronounced neutrophil infiltrates in IRF3-deficient mice. Neutrophil depletion by administration of anti-Ly6G monoclonal antibody indicated that neutrophils play a dominant role in the development of severe liver necrosis in IRF3-deficient mice. Quantification of cytokine genes expression revealed increased liver expression of interleukin (IL)-12/IL-23p40, IL-23p19 messenger RNA (mRNA), and IL-17A mRNA in IRF3-deficient versus wildtype (WT) mice, whereas IL-27p28 mRNA expression was diminished in the absence of IRF3. The increased IL-17 production in IRF3-deficient mice was functionally relevant, as IL-17 neutralization prevented the enhanced hepatocellular damages and liver inflammation in these animals. Evidence for enhanced production of IL-23 and decreased accumulation of IL-27 cytokine in M1 type macrophage from IRF3-deficient mice was also observed after treatment with lipopolysaccharide, a setting in which liver gamma-delta T cells and invariant natural killer T cells were found to be involved in IL-17A hyperproduction.

CONCLUSION

IRF3-dependent events downstream of TLR4 control the IL-23/IL-17 axis in the liver and this regulatory role of IRF3 is relevant to liver ischemia-reperfusion injury.

Human mesenchymal stem cells upregulate CD1dCD5(+) regulatory B cells in experimental autoimmune encephalomyelitis

BACKGROUND/AIMS

Multiple sclerosis (MS) causes significant neurological disability. Experimental autoimmune encephalomyelitis (EAE) is an animal model of MS. Human bone marrow mesenchymal stem cells (hMSCs) possess anti-inflammatory and immunosuppressive effects. We studied whether hMSCs affect CD1d(high)CD5(+) regulatory B-cell activity in EAE.

METHODS

EAE was induced in C57BL/6N mice by immunization with MOG35-55 peptide. hMSCs were injected intravenously into EAE mice on day 3 and day 12 after first immunization. Mice were sacrificed on day 26. Immunohistochemistry of the spinal cord, serum cytokines levels, production of cytokines by cultured splenic cells, and flow cytometry for splenic Th17 and CD1d(high)CD5(+) regulatory B cells were studied.

RESULTS

EAE mice with hMSC treatment on day 3 and day 12 had reduced EAE scores from day 14 to day 26 compared to EAE mice without hMSC treatment, and reduced infiltration of inflammatory cells and demyelination in the spinal cord. EAE mice with hMSC treatment on day 3 and day 12 had: (1) lower serum levels of IL-6, TNF-α (p < 0.0005), and IL-17 (p < 0.005 for day 3, p < 0.0005 for day 12); (2) reduced splenic cell production and secretion of IL-6, TNF-α (p < 0.05), and IL-17 (p < 0.05), and increased splenic production of IL-10; (3) reduced splenic Th17 cells (p < 0.05 for day 3, p < 0.005 for day 12), and (4) increased CD1d(high)CD5(+) regulatory B cells (p < 0.005) compared to EAE mice without hMSC treatment.

CONCLUSION

hMSC treatment on day 3 and day 12 suppresses EAE severity. The underlying mechanisms involve downregulation of Th17 cells and upregulation of CD1d(high)CD5(+) regulatory B-cell activity.

Lithium controls central nervous system autoimmunity through modulation of IFN-γ signaling

Inhibitors of glycogen synthase kinase 3 (GSK3) are being explored as therapy for chronic inflammatory diseases. We previously demonstrated that the GSK inhibitor lithium is beneficial in experimental autoimmune encephalomyelitis (EAE), the mouse model of multiple sclerosis. In this study we report that lithium suppresses EAE induced by encephalitogenic interferon-γ (IFN-γ)-producing T helper (Th1) cells but not by interleukin (IL)-17-producing T helper (Th17) cells. The therapeutic activity of lithium required functional IFN-γ-signaling, but not the receptor for type I IFN (IFNAR). Inhibitor/s of GSK3 attenuated IFN-γ dependent activation of the transcription factor STAT1 in naïve T cells as well as in encephalitogenic T cells and Th1 cells. The inhibition of STAT1 activation was associated with reduced IFN-γ production and decreased expansion of encephalitogenic Th1 cells. Furthermore, lithium treatment induced Il27 expression within the spinal cords of mice with EAE. In contrast, such treatment of Ifngr(-/-) mice did not induce Il27 and was associated with lack of therapeutic response. Our study reveals a novel mechanism for the efficacy of GSK3 targeting in EAE, through the IFN-γ-STAT1 axis that is independent IFNAR-STAT1 axis. Overall our findings set the framework for the use of GSK3 inhibitors as therapeutic agents in autoimmune neuroinflammation.

Cytokine expression and the role of Thl7 cells in mice colitis

BACKGROUND/AIMS

To explore the expression and mechanism of Thl7 cells and cytokines in mice model with 2,4,6-trinitrobenzenesulphonic acid (TNBS)-induced inflammatory bowel disease (IBD).

METHODOLOGY

ELISA assay was used to detect the expression of Th17 cytokine IL-17 and Thl cytokines IFN-y in colon tissues. Western blot assay was applied to detect IL-17 expression in peripheral blood mononuclear cells (PBMC), spleen mononuclear cells (SMC), mesenteric lymph node cells and colon tissue of colitic mice. RT-PCR assay was used to detect the effect of anti-IL-17 antibody application on TNF-a, IFN-y and IL-6 mRNA levels in SMCs from colitic mice.

RESULTS

Th17 cytokine IL-17 and Thl cytokines IFN-y were both expressed at high level in TNBS-induced colitic mice. In addition, the expression of Thl7 cytokine appeared earlier than the Thl cytokine. IL-17 levels in SMCs, mesenteric lymph node cells and colon tissue of the disease model group had significant differences compared with normal control group (p<0.01), while the IL-17 level in PBMCs of the disease model group had no significant difference (p>0.05) to control group. After application of 10 ug/mL anti-IL-7 antibody, the TNF-ct, IL-6 and IFN-y mRNA levels in SMCs of the model group showed no significant difference from that of no antibody group (p>0.05).

CONCLUSIONS

Both Th17 cells and Thl cells involved in TNBS-induced IBD and the role of Thl17 cells may be through inducing the secretion of pro-inflammatory cytokines.

The emerging role of Interleukin 27 in inflammatory arthritis and bone destruction

Although the causes of inflammatory arthritis elude us, aberrant cytokine expression has been linked to joint pathology. Consequently, several approaches in the clinic and/or in clinical trials are targeting cytokines, e.g. tumor necrosis factor (TNF), Interleukin 23 (IL-23) and Interleukin 17 (IL-17), with the goal of antagonizing their respective biologic activity through therapeutic neutralizing antibodies. Such, cytokine signaling-dependent molecular networks orchestrate synovial inflammation on multiple levels including differentiation of myeloid cells to osteoclasts, the central cellular players in arthritis-associated pathologic bone resorption. Hence, understanding of the cellular and molecular mechanisms elicited by synovial cytokine networks that dictate recruitment, differentiation and activation of osteoclast precursors and osteoclasts, respectively, is central to shaping novel therapeutic options for inflammatory arthritis patients. In this article we are discussing the complex signaling interactions involved in the regulation of inflammatory arthritis and it's associated bone loss with a focus on Interleukin 27 (IL-27). The present review will discuss the primary bone-degrading cell, the osteoclast, and on how IL-27, directly or indirectly, modulates osteoclast activity in autoimmune-driven inflammatory joint diseases.

IFN-γ limits Th9-mediated autoimmune inflammation through dendritic cell modulation of IL-27

IL-9-producing Th9 cells have been associated with autoimmune diseases, such as experimental autoimmune encephalitis. However, the factors that negatively regulate Th9 cells during autoimmune inflammation are unclear. In this article, we show that IFN-γ inhibits Th9 differentiation both in vitro and in vivo. This suppressive activity was dependent on the transcription factor STAT-1. In addition to its direct inhibitory effect on Th9 differentiation, IFN-γ suppressed Th9 cells through the induction of IL-27 from dendritic cells. In vitro, treatment of naive CD4(+) T cells with IL-27 suppressed the development of Th9 cells, which was partially dependent on the transcription factors STAT-1 and T-bet. Moreover, IL-27 treatment completely abrogated the encephalitogenicity of Th9 cells in the experimental autoimmune encephalomyelitis model. Thus, our results identify a previously unknown mechanism by which IFN-γ limits Th9-mediated autoimmune inflammation through dendritic cell modulation of IL-27.

Possible roles of IL-12-family cytokines in rheumatoid arthritis

The IL-12 family members, IL-12, IL-23, IL-27 and IL-35, are heterodimeric cytokines that share subunits and have important roles in autoimmunity. As well as their structural relationship the IL-12 family cytokines share some biological characteristics but have functional differences. These cytokines contribute to immune-mediated inflammation and our improved knowledge of their actions has led to alteration of the T(H)1-T(H)2 paradigm. In rheumatoid arthritis (RA), leukocyte migration, bone erosions and angiogenesis are modulated by an IL-23-IL-17 cascade, which can be negated in part by IL-12, IL-27 and IL-35 function. However, the IL-12 family members are a relatively new area of research and data have been generated mostly at the preclinical stage. Further studies in patients with RA are, therefore, required to determine whether these cytokines are valid targets for RA therapy.

Novel IL27p28/IL12p40 cytokine suppressed experimental autoimmune uveitis by inhibiting autoreactive Th1/Th17 cells and promoting expansion of regulatory T cells

IL-12 family cytokines are important in host immunity. Whereas some members (IL-12, IL-23) play crucial roles in pathogenesis of organ-specific autoimmune diseases by inducing the differentiation of Th1 and Th17 lymphocytes, others (IL-27 and IL-35) suppress inflammatory responses and limit tissue injury induced by these T cell subsets. In this study, we have genetically engineered a novel IL27p28/IL12p40 heterodimeric cytokine (p28/p40) that antagonizes signaling downstream of the gp130 receptor. We investigated whether p28/p40 can be used to ameliorate uveitis, a CNS inflammatory disease. Experimental autoimmune uveitis (EAU) is the mouse model of human uveitis and is mediated by Th1 and Th17 cells. We show here that p28/p40 suppressed EAU by inhibiting the differentiation and inflammatory responses of Th1 and Th17 cells while promoting expansion of IL-10(+)- and Foxp3(+)-expressing regulatory T cells. Lymph node cells from mice treated with p28/p40 blocked adoptive transfer of EAU to naïve syngeneic mice by immunopathogenic T cells and suppressive effects of p28/p40 derived in part from antagonizing STAT1 and STAT3 pathways induced by IL-27 and IL-6. Interestingly, IL27p28 also suppressed EAU, but to a lesser extent than p28/p40. The inhibition of uveitogenic lymphocyte proliferation and suppression of EAU by p28/p40 and IL27p28 establish efficacy of single chain and heterodimeric IL-12 family cytokines in treatment of a CNS autoimmune disease. Creation of the biologically active p28/p40 heterodimeric cytokine represents an important proof-of-concept experiment, suggesting that cytokines comprising unique IL-12 α- and β-subunit pairing may exist in nature and may constitute a new class of therapeutic cytokines.

Interferon-γ, tumor necrosis factor, and interleukin-18 cooperate to control growth of Mycobacterium tuberculosis in human macrophages

Mycobacterium tuberculosis (MTB) remains a leading infectious threat to human health. Macrophages are the cells targeted for infection by the bacterium as well as key effector cells for clearance of the pathogen. Interleukin (IL)-27 opposes macrophage-mediated control of MTB because supplying IL-12 and blocking the activity of IL-27 limits bacterial growth in primary human macrophages. The purpose of this study was to determine the immunological regulators of this macrophage mechanism to restrict MTB growth. Interferon (IFN)-γ, TNF-α, and IL-18 were all demonstrated to be important to the environment that limits bacterial growth when IL-12 is supplied and IL-27 is neutralized. We find IL-18 works in conjunction with IL-12 to achieve optimal IFN-γ production in this system. We also demonstrate novel interactions between these cytokines to influence the expression or responsiveness to one another. Quantitative assays show that IFN-γ enhances expression of the IL-18 receptor signaling chain, as well as TNF expression and secretion. In turn, TNF-α augments expression of the receptor for IFN-γ, the amount at the cell surface, and the extent of IFN-γ -induced signaling. We further define how the cytokine environment supports an enhanced state of classical macrophage activation. Collectively, these results describe novel immunological mechanisms that provide additional insights into the effects of IL-12 and IL-27 on macrophage regulation during MTB infection.

IL-27 acts as a priming signal for IL-23 but not IL-12 production on human antigen-presenting cells

IL-27 belongs to the IL-12 family of cytokines and has been described not only to support T-cell polarization along the Th1 lineage, but also to induce important anti-inflammatory responses in later phases of inflammation. We and others have previously shown that the cytokine IL-27 has an important impact on the chronic manifestation of inflammatory skin diseases. Thus, the aim of this study was to specify the effects of IL-27 on the human antigen-presenting cell (APC) subtype inflammatory dendritic epidermal cells (IDEC), which are known to play an important role in eczema. IDEC and blood-derived human macrophages were generated from human peripheral blood and stimulated with IL-27. Functional responses of the cells were analysed by intracellular cytokine staining, ELISA and FlowCytomix. IL-27 was found to be the only IL-12 family member that acts on human APC as a priming signal for IL-23 but not IL-12 production. We confirmed for macrophages that IL-27 limits lipopolysaccharide-induced IL-10 production and detected the same tendency for IDEC. Furthermore, we showed that this also applies to CD40L-induced IL-10 expression in both investigated human APC subsets. We demonstrate that IL-27 exerts pro-inflammatory effects on human APC in particular in the context of a range of bacterial-derived TLR ligands. Hence, our study builds upon the idea that IL-27 exerts a pro-inflammatory effect on innate immune and tissue-resident cells and may drive eczematous reaction - in particular in the context of bacterial superinfection - towards a chronic phase.

Bystanders not so innocent after all

Interleukin 27 (IL-27) regulates immune responses, including T helper 17 (Th17) cell activity. In this issue of Immunity, Hirahara et al. (2012) demonstrate that IL-27 suppresses Th17 cells in trans through induction of the inhibitory ligand PD-L1 on bystander T cells.

Immune response and immunopathology during toxoplasmosis

Toxoplasma gondii is a protozoan parasite of medical and veterinary significance that is able to infect any warm-blooded vertebrate host. In addition to its importance to public health, several inherent features of the biology of T. gondii have made it an important model organism to study host-pathogen interactions. One factor is the genetic tractability of the parasite, which allows studies on the microbial factors that affect virulence and allows the development of tools that facilitate immune studies. Additionally, mice are natural hosts for T. gondii, and the availability of numerous reagents to study the murine immune system makes this an ideal experimental system to understand the functions of cytokines and effector mechanisms involved in immunity to intracellular microorganisms. In this article, we will review current knowledge of the innate and adaptive immune responses required for resistance to toxoplasmosis, the events that lead to the development of immunopathology, and the natural regulatory mechanisms that limit excessive inflammation during this infection.

The dual roles of inflammatory cytokines and chemokines in the regulation of autoimmune diseases and their clinical implications

Cytokines and chemokines are secreted, small cell-signaling protein molecules, whose receptors are expressed on immune cells. These factors play a critical role in immune cell differentiation, migration, and polarization into functional subtypes and in directing their biological functions. Much attention has been devoted to exploring the role of key inflammatory cytokines and promigratory chemokines in autoimmune, autoinflammatory, and allergic diseases, leading to development of therapeutic strategies that are based on their targeted neutralization. Recent studies, including those coming from our groups, show that several major proinflammatory cytokines and chemokines, including IFN-γ, IL-2, CCL2, and CXCL12, may also function as anti-inflammatory mediators and therefore, may have potential as anti-inflammatory drugs. Likewise, major anti-inflammatory mediators, such as TGF-β, may under certain conditions, in combination with other cytokines, exhibit proinflammatory function and direct the polarization of the highly inflammatory CD4(+) Th17 cells. We show here that the biological function of pro- and anti-inflammatory cytokines is dependent on three key parameters: the local concentration of a given cytokine, the stage of disease in which it is administered, and its combination with other cytokines. The therapeutic implications of these findings are discussed, including two very recent studies summarizing clinical trials, in which low-dose administration of IL-2 was used to successfully suppress HCV and GVHD.

Osteopontin promotes inflammation in patients with acute coronary syndrome through its activity on IL-17 producing cells

Atherosclerosis is a progressive disease with a strong inflammatory component. Here we confirm the existence of a critical imbalance in the ratio of Th17 to Treg-cell populations in peripheral CD4(+) T cells from patients with acute coronary syndrome (ACS), which favors inflammation. This was concurrent with increased IL-17 production from the CD4(+) CD45RA(-) FOXP3(lo) Treg-cell subset, and elevated osteopontin (OPN) levels in serum from ACS patients. We demonstrate a direct effect of OPN in serum from ACS patients on increased IL-17 production by CD4(+) CD45RA(-) FOXP3(lo) T cells, mediated through recruitment of the OPN receptors CD29 and CD44, and dependent on STAT3 and the nuclear hormone receptor retinoic-acid-related orphan receptor-γt (RORγt) pathway, but not IL-6 production. To our knowledge and beyond the disease context of ACS, this study constitutes the first demonstration of a critical role for OPN in the positive regulation of inflammation through increased IL-17 production by CD4(+) CD45RA(-) FOXP3(lo) cells.

Interleukin-27 receptor limits atherosclerosis in Ldlr-/- mice

RATIONALE

Atherosclerosis is a chronic inflammatory disease of the arterial wall. Several proinflammatory cytokines are known to promote atherosclerosis, but less is known about the physiological role of anti-inflammatory cytokines. Interleukin (IL)-27 is a recently discovered member of the IL-6/IL-12 family. The IL-27 receptor is composed of IL-27 receptor A (WSX-1) and gp130 and is required for all established IL-27 signaling pathways. The expression of the IL-27 subunit Ebi3 is elevated in human atheromas, yet its function in atherosclerosis remains unknown.

OBJECTIVE

The aim of this study was to test the role of IL-27 receptor signaling in immune cells in atherosclerosis development.

METHODS AND RESULTS

Atherosclerosis-prone Ldlr(-/-) mice transplanted with Il27ra(-/-) bone marrow and fed Western diet for 16 weeks developed significantly larger atherosclerotic lesions in aortic roots, aortic arches, and abdominal aortas. Augmented disease correlated with increased accumulation of CD45(+) leukocytes and CD4(+) T cells in the aorta, which produced increased amounts of IL-17A and tumor necrosis factor. Several chemokines, including CCL2, were upregulated in the aortas of Ldlr(-/-) mice receiving Il27ra(-/-) bone marrow, resulting in accumulation of CD11b(+) and CD11c(+) macrophages and dendritic cells in atherosclerotic aortas.

CONCLUSIONS

The absence of anti-inflammatory IL-27 signaling skews immune responses toward T-helper 17, resulting in increased production of IL-17A and tumor necrosis factor, which in turn enhances chemokine expression and drives the accumulation of proatherogenic myeloid cells in atherosclerotic aortas. These findings establish a novel antiatherogenic role for IL-27 receptor signaling, which acts to suppress the production of proinflammatory cytokines and chemokines and to curb the recruitment of inflammatory myeloid cells into atherosclerotic aortas.

Immunobiology of visceral leishmaniasis

Visceral leishmaniasis (VL), commonly known as kala-azar, is caused by Leishmania donovani and Leishmania infantum (Leishmania chagasi in the Americas). These Leishmania species infect macrophages throughout the viscera, and parasites are typically found in the spleen, liver, and bone marrow. Patients with active disease typically exhibit marked immunosuppression, lack reactivity to the Leishmania skin test (LST), a delayed type hypersensitivity test, and their peripheral blood mononuclear cells (PBMC) fail to respond when stimulated with leishmanial antigens in vitro. However, most people infected with visceralizing species of Leishmania never develop disease. Understanding immune failure and the underlying immune mechanism that lead to disease as well as control of infection are key questions for research in this field. In this review, we discuss immunological events described in human and experimental VL and how these can affect the outcome of infection.

Pilot study of interleukin-27 in pathogenesis of dermatomyositis and polymyositis: associated with interstitial lung diseases

OBJECTIVE

To determine whether interleukin (IL)-27 is involved in dermatomyositis (DM) and polymyositis (PM).

METHODS

Serum IL-27, IL-18 and interferon-γ (IFN-γ) levels in 37 DM and 15 PM were detected by enzyme-linked immunosorbent assay (ELISA).

RESULTS

Serum IL-27, IL-18 and IFN-γ levels were significantly higher in DM and PM patients than in healthy controls. Significant higher levels of IL-27 were found in high creatine kinase (CK) level group and in patients with interstitial lung disease (ILD). Level of IL-27 was correlated with global 100-mm visual analog scales (VASs) score in patients with PM.

CONCLUSION

These data supports the hypothesis that IL-27 maybe involved in DM and PM pathogenesis.

Inborn errors of human STAT1: allelic heterogeneity governs the diversity of immunological and infectious phenotypes

The genetic dissection of various human infectious diseases has led to the definition of inborn errors of human STAT1 immunity of four types, including (i) autosomal recessive (AR) complete STAT1 deficiency, (ii) AR partial STAT1 deficiency, (iii) autosomal dominant (AD) STAT1 deficiency, and (iv) AD gain of STAT1 activity. The two types of AR STAT1 defect give rise to a broad infectious phenotype with susceptibility to intramacrophagic bacteria (mostly mycobacteria) and viruses (herpes viruses at least), due principally to the impairment of IFN-γ-mediated and IFN-α/β-mediated immunity, respectively. Clinical outcome depends on the extent to which the STAT1 defect decreases responsiveness to these cytokines. AD STAT1 deficiency selectively predisposes individuals to mycobacterial disease, owing to the impairment of IFN-γ-mediated immunity, as IFN-α/β-mediated immunity is maintained. Finally, AD gain of STAT1 activity is associated with autoimmunity, probably owing to an enhancement of IFN-α/β-mediated immunity. More surprisingly, it is also associated with chronic mucocutaneous candidiasis, through as yet undetermined mechanisms involving an inhibition of the development of IL-17-producing T cells. Thus, germline mutations in human STAT1 define four distinct clinical disorders. Various combinations of viral, mycobacterial and fungal infections are therefore allelic at the human STAT1 locus. These experiments of Nature neatly highlight the clinical and immunological impact of the human genetic dissection of infectious phenotypes.

Cutting edge: suppression of GM-CSF expression in murine and human T cells by IL-27

GM-CSF is a potent proinflammatory cytokine that plays a pathogenic role in the CNS inflammatory disease experimental autoimmune encephalomyelitis. As IL-27 alleviates experimental autoimmune encephalomyelitis, we hypothesized that IL-27 suppresses GM-CSF expression by T cells. We found that IL-27 suppressed GM-CSF expression in CD4+ and CD8+ T cells in splenocyte and purified T cell cultures. IL-27 suppressed GM-CSF in Th1, but not Th17, cells. IL-27 also suppressed GM-CSF expression by human T cells in nonpolarized and Th1- but not Th17-polarized PBMC cultures. In vivo, IL-27p28 deficiency resulted in increased GM-CSF expression by CNS-infiltrating T cells during Toxoplasma gondii infection. Although in vitro suppression of GM-CSF by IL-27 was independent of IL-2 suppression, IL-10 upregulation, or SOCS3 signaling, we observed that IL-27-driven suppression of GM-CSF was STAT1 dependent. Our findings demonstrate that IL-27 is a robust negative regulator of GM-CSF expression in T cells, which likely inhibits T cell pathogenicity in CNS inflammation.

Gene therapy using IL-27 ameliorates Sjögren's syndrome-like autoimmune exocrinopathy

Introduction

Sjögren's syndrome (SjS) is a systemic autoimmune disease characterized by decreased salivary and lacrimal gland secretions, resulting in severe dry mouth and dry eyes. Recent studies have suggested that T_H17 cells and its signature cytokine IL-17 are involved in the underlying pathogenic mechanisms leading to destructive inflammation and autoimmunity. In the present study, we examined whether IL-27, a natural inhibitor of T_H17 activity, could down-regulate or reverse SjS in C57BL/6.NOD-Aec1Aec2 mice, a model of primary-SjS.

Methods

Recombinant serotype 2 adeno-associated viral (AAV2) vectors expressing either IL-27 (rAAV2-IL27) or LacZ (rAAV2-LacZ) were injected into 6 or 14 week-old C57BL/6.NOD-Aec1Aec2 mice. Changes in IL-27, IL-17, and IL-10 cytokine levels in peripheral blood were determined by ELISAs, while flow cytometry analyses were used to quantify cytokine-positive splenocytes. Histological assessment of salivary glands, anti-nuclear autoantibody (ANA) staining, and stimulated saliva flow rates were used to profile SjS disease severity.

Results

Mice systemically treated with intravenous rAAV2-IL27 injections at either 6 or 14 weeks of age exhibited long-term elevated levels of serum IL-27 with concomitantly reduced levels of IL-17 compared with sera from mice injected with rAAV2-LacZ or saline out to 20 weeks post-inoculation. Most importantly, disease profiles revealed that rAAV2-IL27 treatment had little effect on lymphocytic focus (LF) scores, but resulted in structural changes in LF, lower titers of ANAs with changes in staining patterns, and a less severe clinical disease as determined by saliva flow rates.

Conclusions

These data support the concept that IL-27, when provided exogenously, can induce a suppressive effect on SjS development and thus may be an effective therapeutic agent for regulating T_H17 pro-inflammatory activity in autoimmune diseases where the T_H17 system has been shown to play an important role in their pathogenesis.

Elevated circulating interleukin-27 in patients with coronary artery disease is associated with dendritic cells, oxidized low-density lipoprotein, and severity of coronary artery stenosis

Coronary artery disease (CAD) is an immune-mediated chronic inflammatory disease mainly caused by atherosclerosis. The aims of this study were to investigate the role of interleukin-27 (IL-27) in patients with CAD and the severity of coronary artery lesions, which was evaluated by Gensini score and to investigate the biosynthesis of IL-27 and oxidized low-density lipoprotein (ox-LDL) in vitro using monocyte-derived dendritic cells (DCs). To this aim, plasma levels of IL-27, ox-LDL, and Gensini score were analyzed in patients with CAD (n = 136) and normal subjects (controls, n = 29). IL-27 concentration of the supernatant and the mRNA expression levels of p28 and ebi3, subunits of IL-27, from cultured immature DCs incubated with different concentrations of ox-LDL for 24 h were also analyzed. We found that circulating IL-27 levels were significantly elevated in patients with CAD than in controls (P < 0.01), and positively correlated to ox-LDL and Gensini score. ox-LDL dose-dependently upregulated expression of both IL-27 protein and IL-27 (p28 and EBI3) mRNA in vitro, indicating that ox-LDL can stimulate DCs to produce IL-27. These results demonstrate that IL-27 might regulate the network of immunity and inflammation in the pathogenesis of atherosclerosis.

Rather than interleukin-27, interleukin-6 expresses positive correlation with liver severity in naïve hepatitis B infection patients

AIMS

Effective cytokines can drive the commitment of naive T cells to regulate immune response after antigen-mediated activation. Aims are to elucidate the clinical role of serum IL-27 and IL-6 in the different stages of naïve hepatitis B virus (HBV)-infected patients.

METHODS

Samples with well-characterized clinical profiles were assessed from 395 HBV-infected patients including chronic hepatitis B (CHB) group in 291 patients, liver cirrhosis (LC) group in 57 patients, hepatocellular carcinoma (HCC) group in 47 patients. Another 139 non-HBV infected individuals were enrolled as control group (CG) including 104 with normal liver function (NF) and 35 with liver dysfunction (LD).

RESULTS

The HBV-infected group and separated groups presented significantly higher IL-27 and IL-6 expression than the CG or subgroups of CG. In contrast to IL-27, IL-6 showed significant differences with deteriorating liver condition compared with LC or HCC with CHB groups. Furthermore, IL-6, rather than IL-27, showed significant statistical differences in patients with advanced liver disease compared with those of mild or moderate to severe liver disease and in patients with terminal stage HCC compared with those of early to intermediate or advanced stage HCC. The data associated with liver function, including Albumin, Bilirubin, INR, Platelet and AFP levels, were significantly correlated to IL-6 expression, but had weak correlation to IL-27 expression in HBV patients.

CONCLUSION

Serum IL-27 can trigger immune response to prevent hepatic injury in different clinical-pathologic stages of HBV-infected patients earlier, but IL-6 may play an extremely important role to determine the liver progression.

Interleukin-27 priming of T cells controls IL-17 production in trans via induction of the ligand PD-L1

Interleukin-27 (IL-27) is a key immunosuppressive cytokine that counters T helper 17 (Th17) cell-mediated pathology. To identify mechanisms by which IL-27 might exert its immunosuppressive effect, we analyzed genes in T cells rapidly induced by IL-27. We found that IL-27 priming of naive T cells upregulated expression of programmed death ligand 1 (PD-L1) in a signal transducer and activator of transcription 1 (STAT1)-dependent manner. When cocultured with naive CD4(+) T cells, IL-27-primed T cells inhibited the differentiation of Th17 cells in trans through a PD-1-PD-L1 interaction. In vivo, coadministration of naive TCR transgenic T cells (2D2 T cells) with IL-27-primed T cells expressing PD-L1 inhibited the development of Th17 cells and protected from severe autoimmune encephalomyelitis. Thus, these data identify a suppressive activity of IL-27, by which CD4(+) T cells can restrict differentiation of Th17 cells in trans.

IL-27 Regulates IL-18 binding protein in skin resident cells

IL-18 is an important mediator involved in chronic inflammatory conditions such as cutaneous lupus erythematosus, psoriasis and chronic eczema. An imbalance between IL-18 and its endogenous antagonist IL-18 binding protein (BP) may account for increased IL-18 activity. IL-27 is a cytokine with dual function displaying pro- and anti-inflammatory properties. Here we provide evidence for a yet not described anti-inflammatory mode of action on skin resident cells. Human keratinocytes and surprisingly also fibroblasts (which do not produce any IL-18) show a robust, dose-dependent and highly inducible mRNA expression and secretion of IL-18BP upon IL-27 stimulation. Other IL-12 family members failed to induce IL-18BP. The production of IL-18BP peaked between 48-72 h after stimulation and was sustained for up to 96 h. Investigation of the signalling pathway showed that IL-27 activates STAT1 in human keratinocytes and that a proximal GAS site at the IL-18BP promoter is of importance for the functional activity of IL-27. The data are in support of a significant anti-inflammatory effect of IL-27 on skin resident cells. An important novel property of IL-27 in skin pathobiology may be to counter-regulate IL-18 activities by acting on keratinocytes and importantly also on dermal fibroblasts.

Th17 cells: biology, pathogenesis of autoimmune and inflammatory diseases, and therapeutic strategies

Th17 cells that secrete the cytokines IL-17A and IL-17F and express lineage-specific transcription factor RORC (RORγt in mice) represent a distinct lineage of CD4(+) T cells. Transforming growth factor-β and inflammatory cytokines, such as IL-6, IL-21, IL-1β, and IL-23, play central roles in the generation of Th17 cells. Th17 cells are critical for the clearance of extracellular pathogens, including Candida and Klebsiella. However, under certain conditions, these cells and their effector molecules, such as IL-17, IL-21, IL-22, GM-CSF, and CCL20, are associated with the pathogenesis of several autoimmune and inflammatory diseases, such as rheumatoid arthritis, systemic lupus erythematosus, multiple sclerosis, psoriasis, inflammatory bowel disease, and allergy and asthma. This review discusses these disease states and the various therapeutic strategies under investigation to target Th17 cells, which include blocking the differentiation and amplification of Th17 cells, inhibiting or neutralizing the cytokines of Th17 cells, and suppressing the transcription factors specific for Th17 cells.

AAV2-mediated subretinal gene transfer of mIL-27p28 attenuates experimental autoimmune uveoretinitis in mice

Background

Advances in gene transfer techniques have provided long-term, safe and stable transduction of retinal cells following subretinal injection with adeno-associated viral (AAV) vectors. In this study we investigated whether subretinal injection of AAV2-murine IL-27p28 vector was effective in inhibiting experimental autoimmune uveoretinitis (EAU) induced in B10RIII mice.

Methodology/Principal Findings

An AAV2 vector encoding the murine IL-27p28 gene (rAAV2-CMV-mIL-27p28) was prepared and subretinally injected into B10RIII mice (4.35×10⁸ vector genome (v.g.)). AAV2 vector mediating green fluorescent protein (rAAV2-CMV-GFP) served as a control (5×10⁸ v.g.). The concentration of mIL-27p28 in homogenized eyes and serum was assayed by enzyme linked immunosorbent assay (ELISA) after subretinal injection. Human IRBP_161–180 peptide and Complete Freund’s Adjuvant were injected into mice receiving either the rAAV2-CMV-mIL-27p28 or rAAV2-CMV-GFP vector. EAU was evaluated clinically and pathologically. The level of IL-17 and IL-10 in homogenized eyes was measured on day 12 and day 21 following immunization. Delayed type hypersensitivity (DTH) and IRBP_161–180–specific proliferation of lymphocytes from the spleen and lymph nodes were assayed to examine the influence of the subretinal delivery of rAAV2-CMV-mIL-27p28 on the systemic immune response. IL-27p28 was detectable by ELISA within the eyes from two weeks following subretinal injection of the rAAV2-CMV-mIL-27p28 vector and showed a sustained high expression from day 14 to 9 months with a highest expression at 5 months. Subretinal injection of the vector significantly attenuated the severity of EAU disease clinically and pathologically in association with a significantly decreased IL-17 expression and an increased IL-10 expression. The IL-27p28 vector did not affect the systemic immune response, as determined by DTH and IRBP_161–180–specific lymphocyte proliferation.

Conclusions/Significance

A high and stable expression of IL-27p28 was observed for at least 9 months following subretinal delivery of rAAV2-CMV-mIL-27p28. The amelioration of EAU disease severity was associated with a decreased IL-17 expression and an increased IL-10 expression.

Steroid-like signalling by interferons: making sense of specific gene activation by cytokines

Many cytokines, hormones and growth factors use the JAK (Janus kinase)/STAT (signal transducer and activator of transcription) pathway for cell signalling and specific gene activation. In the classical model, ligand is said to interact solely with the receptor extracellular domain, which triggers JAK activation of STATs at the receptor cytoplasmic domain. Activated STATs are then said to carry out nuclear events of specific gene activation. Given the limited number of STATs (seven) and the activation of the same STATs by cytokines with different functions, the mechanism of the specificity of their signalling is not obvious. Focusing on IFNγ (interferon γ), we have shown that ligand, receptor and activated JAKs are involved in nuclear events that are associated with specific gene activation, where the receptor subunit IFNGR1 (IFNγ receptor 1) functions as a transcription/co-transcription factor and the JAKs are involved in key epigenetic events. RTKs (receptor tyrosine kinases) such as EGFR [EGF (epidermal growth factor) receptor] and FGFR [FGF (fibroblast growth factor) receptor] also undergo nuclear translocation in association with their respective ligands. EGFR and FGFR, like IFNGR1, have been shown to function as transcription/co-transcription factors. The RTKs also regulate other kinases that have epigenetic effects. Our IFNγ model, as well as the RTKs EGFR and FGFR, have similarities to that of steroid receptor signalling. These systems consist of ligand-receptor-co-activator complexes at the genes that they activate. The co-activators consist of transcription factors and kinases, of which the latter play an important role in the associated epigenetics. It is our view that signalling by cytokines such as IFNγ is but a variation of specific gene activation by steroid hormones.

Regulation of TH17 cell differentiation by innate immune signals

Upon antigen stimulation, naive T helper cells differentiate into distinct lineages to attain specialized properties and effector functions. T(H)17 cells, a recently identified lineage of CD4(+) effector T cells, play a key role in the immune defense against fungi and extracellular bacteria, but also contribute to the pathogenesis of many autoimmune conditions. The differentiation of T(H)17 cells is orchestrated by an intricate network of signaling pathways and transcriptional regulators in T cells. While the involvement of T cell-intrinsic pathways has been described extensively, we are just beginning to appreciate how T(H)17 cell development is shaped by extrinsic pathways, especially the innate immune signals. Dendritic cells (DCs), the most important cell type to bridge innate and adaptive immunity, drive T(H)17 cell differentiation by providing antigenic, costimulatory and cytokine signals. This is mediated by the recognition of innate and inflammatory signals by DCs via pattern recognition receptors, cytokine receptors and other immunomodulatory receptors that in turn activate the intracellular signaling network. In particular, p38α MAP kinase has emerged as a critical pathway to program DC-dependent T(H)17 cell differentiation by integrating multiple instructive signals in DCs. Here, we summarize the current knowledge on the mechanisms by which DC-derived innate immune signals drive T(H)17 cell differentiation.

Mice deficient in STAT1 but not STAT2 or IRF9 develop a lethal CD4+ T-cell-mediated disease following infection with lymphocytic choriomeningitis virus

Interferon (IFN) signaling is crucial for antiviral immunity. While type I IFN signaling is mediated by STAT1, STAT2, and IRF9, type II IFN signaling requires only STAT1. Here, we studied the roles of these signaling factors in the host response to systemic infection with lymphocytic choriomeningitis virus (LCMV). In wild-type (WT) mice and mice lacking either STAT2 or IRF9, LCMV infection was nonlethal, and the virus either was cleared (WT) or established persistence (STAT2 knockout [KO] and IRF9 KO). However, in the case of STAT1 KO mice, LCMV infection was lethal and accompanied by severe multiorgan immune pathology, elevated expression of various cytokine genes in tissues, and cytokines in the serum. This lethal phenotype was unaltered by the coabsence of the gamma interferon (IFN-γ) receptor and hence was not dependent on IFN-γ. Equally, the disease was not due to a combined defect in type I and type II IFN signaling, as IRF9 KO mice lacking the IFN-γ receptor survived infection with LCMV. Clearance of LCMV is mediated normally by CD8(+) T cells. However, the depletion of these cells in LCMV-infected STAT1 KO mice was delayed, but did not prevent, lethality. In contrast, depletion of CD4(+) T cells prevented lethality in LCMV-infected STAT1 KO mice and was associated with a reduction in tissue immune pathology. These studies highlight a fundamental difference in the role of STAT1 versus STAT2 and IRF9. While all three factors are required to limit viral replication and spread, only STAT1 has the unique function of preventing the emergence of a lethal antiviral CD4(+) T-cell response.

Complement activation product C5a is a selective suppressor of TLR4-induced, but not TLR3-induced, production of IL-27(p28) from macrophages

There is accumulating evidence that the complement activation product, C5a, can orchestrate cellular immune functions. IL-27(p28/EBI3) is an emerging key player essential for regulating inflammatory responses and T cells. In this article, we report that C5a robustly suppressed IL-27(p28) gene expression and release in peritoneal macrophages. These cells from C57BL/6J mice abundantly produced IL-27(p28) after engagement of either the TLR3 (polyinosinic-polycytidylic acid) or TLR4 (LPS) receptor. Genetic deficiency of either TLR4 or LBP completely incapacitated the ability of macrophages to secrete IL-27(p28) in response to LPS. IL-27(p28)-producing macrophages also expressed the C5aR receptor, thus displaying an IL-27(p28)(+)F4/80(+)C5aR(+) phenotype. C5a suppressed IL-27(p28) in LPS-stimulated macrophages via interactions with the C5aR receptor rather than the C5L2 receptor. After endotoxemia, C5aR(-/-) mice displayed higher plasma levels of IL-27(p28) compared with C57BL/6J mice. C5a did not affect the release of IL-27(p28) or the frequency of IL-27(p28)(+)F4/80(+) macrophages after engagement of TLR3. Mechanistically, LPS activated both the NF-κB and the PI3K/Akt pathways, whereas C5a activated only the PI3K/Akt pathway. Engagement of PI3K/Akt was inhibitory for IL-27(p28) production, because PI3K/Akt pharmacologic blockade resulted in increased amounts of IL-27(p28) and reversed the suppressive effects of C5a. Blockade of PI3K/Akt in endotoxemic C57BL/6J mice resulted in higher generation of IL-27(p28). In contrast, the PI3K/Akt pathway was not involved in TLR3-mediated release of IL-27(p28). These data provide new evidence about how complement activation may selectively interfere with production of T cell regulatory cytokines by APCs in the varying contexts of either bacterial (TLR4 pathway) or viral (TLR3 pathway) infection.

Interleukin-30: a novel antiinflammatory cytokine candidate for prevention and treatment of inflammatory cytokine-induced liver injury

The liver is the major metabolic organ and is subjected to constant attacks from chronic viral infection, uptake of therapeutic drugs, life behavior (alcoholic), and environmental contaminants, all of which result in chronic inflammation, fibrosis, and, ultimately, cancer. Therefore, there is an urgent need to discover effective therapeutic agents for the prevention and treatment of liver injury, the ideal drug being a naturally occurring biological inhibitor. Here we establish the role of IL30 as a potent antiinflammatory cytokine that can inhibit inflammation-induced liver injury. In contrast, interleukin (IL)27, which contains IL30 as a subunit, is not hepatoprotective. Interestingly, IL30 is induced by the proinflammatory signal such as IL12 through interferon-gamma (IFN-γ)/signal transducer and activator of transcription 1 signaling. In animal models, administration of IL30 by way of a gene therapy approach prevents and treats both IL12-, IFN-γ-, and concanavalin A-induced liver toxicity. Likewise, immunohistochemistry analysis of human tissue samples revealed that IL30 is highly expressed in hepatocytes, yet barely expressed in inflammation-induced tissue such as fibrous/connective tissue.

CONCLUSION

These novel observations reveal a novel role of IL30 as a therapeutic cytokine that suppresses proinflammatory cytokine-associated liver toxicity.

IL-27 induction of IL-21 from human CD8+ T cells induces granzyme B in an autocrine manner

Interleukin (IL)-27 exerts an anti-inflammatory effect on human and mice CD4(+) T cells by inducing IL-10-producing T regulatory 1 cells through induction of IL-21. However, the role of IL-27 and how it regulates IL-21 from human CD8(+) T cells is unclear. Here, we show that the IL-27 receptor is expressed on human CD8(+) T cells and stimulation of human naïve CD8(+) T cells in the presence of IL-27 leads to an increase in IL-21 and interferon (IFN)-γ production. IL-21 induction in IL-27-stimulated human CD8(+) T cells correlates specifically with expression of the transcription factor T-bet. IL-27 stimulation of naïve CD8(+) T cells induces a double-positive T-bet(+) IL-21(+) expressing CD8(+) T-cell population. Furthermore, IL-27 stimulation of human naïve CD8(+) T cells greatly increases expression of granzyme B. Antibody-mediated neutralization of IL-21 abrogates IL-27-induced granzyme B expression. Moreover, direct addition of IL-21 greatly amplifies granzyme B expression in human naïve CD8(+) T cells. Our findings identify IL-27-induced IL-21 as a key autocrine regulator of granzyme B expression in human CD8(+) T cells.

Increased Th17 and regulatory T cell responses in EBV-induced gene 3-deficient mice lead to marginally enhanced development of autoimmune encephalomyelitis

EBV-induced gene 3 (EBI3)-encoded protein can form heterodimers with IL-27P28 and IL-12P35 to form IL-27 and IL-35. IL-27 and IL-35 may influence autoimmunity by inhibiting Th17 differentiation and facilitating the inhibitory roles of Foxp3(+) regulatory T (Treg) cells, respectively. In this study, we have evaluated the development of experimental autoimmune encephalomyelitis (EAE) in EBI3-deficient mice that lack both IL-27 and IL-35. We found that myelin oligodendrocyte glycoprotein peptide immunization resulted in marginally enhanced EAE development in EBI3-deficient C57BL6 and 2D2 TCR-transgenic mice. EBI3 deficiency resulted in significantly increased Th17 and Th1 responses in the CNS and increased T cell production of IL-2 and IL-17 in the peripheral lymphoid organs. EBI3-deficient and -sufficient 2D2 T cells had equal ability in inducing EAE in Rag1(-/-) mice; however, more severe disease was induced in EBI3(-/-)Rag1(-/-) mice than in Rag1(-/-) mice by 2D2 T cells. EBI3-deficient mice had increased numbers of CD4(+)Foxp3(+) Treg cells in peripheral lymphoid organs. More strikingly, EBI3-deficient Treg cells had more potent suppressive functions in vitro and in vivo. Thus, our data support an inhibitory role for EBI3 in Th17, Th1, IL-2, and Treg responses. Although these observations are consistent with the known functions of IL-27, the IL-35 contribution to the suppressive functions of Treg cells is not evident in this model. Increased Treg responses in EBI3(-/-) mice may explain why the EAE development is only modestly enhanced compared with wild-type mice.

Signaling via the kinase p38α programs dendritic cells to drive TH17 differentiation and autoimmune inflammation

Dendritic cells (DCs) bridge innate and adaptive immunity, but how DC-derived signals regulate T cell lineage choices remains unclear. We report that p38α MAP kinase programs DCs to drive T_H17 differentiation. Deletion of p38α in DCs, but not macrophages or T cells, protects mice from T_H17-mediated autoimmune neuroinflammation. p38α orchestrates expression of cytokines and co-stimulatory molecules in DCs, and further imprints T cell IL-23R signaling to promote T_H17 differentiation. Moreover, p38α is required for tissue-infiltrating DCs to sustain T_H17 responses. This activity of p38α is conserved between mouse and human DCs, and is dynamically regulated by pattern recognition and fungal infection. Our results identify p38α as a central pathway to integrate instructive signals in DCs for T_H17 differentiation and inflammation.

The immunobiology of IL-27

Like many cytokines, IL-27 has pleiotropic properties that can limit or enhance ongoing immune responses depending on context. Thus, under certain circumstances, IL-27 can promote TH1 differentiation and has been linked to the activation of CD8(+) T cells and enhanced humoral responses. However, IL-27 also has potent inhibitory properties and mice that lack IL-27 mediated signaling develop exaggerated inflammatory responses in the context of infection or autoimmunity. This chapter reviews in depth the biology of IL-27, including the initial discovery, characterization, and signaling mediated by IL-27 as well as more recent insights into the molecular and cellular basis for its pleiotropic effects. Many of these advances are relevant to human diseases and highlight the potential of therapies that harness the regulatory properties of IL-27.

Th17 cell accumulation is decreased during chronic experimental colitis by (n-3) PUFA in Fat-1 mice

During colon inflammation, Th17 cells and immunosuppressive regulatory T cells (Treg) are thought to play promotive and preventative roles, respectively. Dietary (n-3) PUFA favorably modulate intestinal inflammation in part by downregulating T-cell activation and functionality. We used the Fat-1 mouse, a genetic model that synthesizes long-chain (n-3) PUFA de novo, to test the hypothesis that (n-3) PUFA protect against colonic inflammation by modulating the polarization of Treg and Th17 cells during colitis. Male and female wild-type (WT) and Fat-1 mice were administered dextran sodium sulfate (DSS) in the drinking water (2.5%) to induce acute (5 d DSS) or chronic (3 cycles DSS) colitis and the percentage of Treg and Th17 cells residing locally [colonic lamina propria (cLP)] and systemically (spleen) was determined by flow cytometry. The percentage of Treg in either tissue site was unaffected by genotype (P > 0.05); however, during chronic colitis, the percentage of Th17 cells residing in both the spleen and cLP was lower in Fat-1 mice compared to WT mice (P < 0.05). Colonic mucosal mRNA expression of critical Th17 cell cytokines and chemokine receptors (IL-17F, IL-21, and CCR6) were lower, whereas expression of the Th17 cell suppressive cytokine, IL-27, was greater in Fat-1 mice compared to WT mice during chronic colitis (P < 0.05). Moreover, colon histological scores were improved in Fat-1 mice (P < 0.05). Collectively, these results demonstrate for the first time, to our knowledge, that (n-3) PUFA can modulate the colonic mucosal microenvironment to suppress Th17 cell accumulation and inflammatory damage following the induction of chronic colitis.

Memory CD4 T cells induce selective expression of IL-27 in CD8+ dendritic cells and regulate homeostatic naive T cell proliferation

Naive T cells undergo robust proliferation in lymphopenic conditions, whereas they remain quiescent in steady-state conditions. However, a mechanism by which naive T cells are kept from proliferating under steady-state conditions remains unclear. In this study, we report that memory CD4 T cells are able to limit naive T cell proliferation within lymphopenic hosts by modulating stimulatory functions of dendritic cells (DC). The inhibition was mediated by IL-27, which was primarily expressed in CD8(+) DC subsets as the result of memory CD4 T cell-DC interaction. IL-27 appeared to be the major mediator of inhibition, as naive T cells deficient in IL-27R were resistant to memory CD4 T cell-mediated inhibition. Finally, IL-27-mediated regulation of T cell proliferation was also observed in steady-state conditions as well as during Ag-mediated immune responses. We propose a new model for maintaining peripheral T cell homeostasis via memory CD4 T cells and CD8(+) DC-derived IL-27 in vivo.

New directions in the basic and translational biology of interleukin-27

Interleukin (IL)-27 is a member of the IL-6 and IL-12 family composed of the IL-27p28 and Epstein-Barr virus-induced gene 3 (EBI3) subunits. Although IL-27 was originally identified as a proinflammatory factor, subsequent studies have revealed the pleiotropic nature of this cytokine. This review discusses recent work that has explored the effect of IL-27 on CD4(+) T cell subsets, including T regulatory type 1 (Tr-1) cells, T follicular helper cells (Tfhs), and forkhead box P3 (Foxp3)(+) T regulatory cells (Tregs). Additionally, we highlight studies that have identified a role for the IL-27p28 subunit as a cytokine receptor antagonist. Much of the recent work on IL-27 has been relevant to human disease states characterized by inappropriate or excessive inflammation, and this review discusses potential opportunities to use IL-27 as a therapeutic agent.

Type I IFN promotes IL-10 production from T cells to suppress Th17 cells and Th17-associated autoimmune inflammation

Whereas the immune system is essential for host defense against pathogen infection or endogenous danger signals, dysregulated innate and adaptive immune cells may facilitate harmful inflammatory or autoimmune responses. In the CNS, chronic inflammation plays an important role in the pathogenesis of neurodegenerative diseases such as multiple sclerosis (MS). Our previous study has demonstrated a critical role for the type I IFN induction and signaling pathways in constraining Th17-mediated experimental autoimmune encephalomyelitis (EAE), an animal model of human MS. However, it remains unknown if self-reactive Th17 cells can be reprogrammed to have less encephalitogenic activities or even have regulatory effects through modulation of innate pathways. In this study, we investigated the direct effects of type I IFN on Th17 cells. Our data show that IFNβ treatment of T cells cultured under Th17 polarizing conditions resulted in reduced production of IL-17, but increased production of IL-10. We also found that IFNβ induced IL-10 production by antigen specific T cells derived from immunized mice. Furthermore, IFNβ treatment could suppress the encephalitogenic activity of myelin-specific T cells, and ameliorate clinical symptoms of EAE in an adoptive transfer model. Together, results from this study suggest that IFNβ may induce antigen-specific T cells to produce IL-10, which in turn negatively regulate Th17-mediate inflammatory and autoimmune response.