The immunobiology of IL-27

Cytomegalovirus-Specific IL-10-Producing CD4+ T Cells Are Governed by Type-I IFN-Induced IL-27 and Promote Virus Persistence

CD4⁺ T cells support host defence against herpesviruses and other viral pathogens. We identified that CD4⁺ T cells from systemic and mucosal tissues of hosts infected with the β-herpesviridae human cytomegalovirus (HCMV) or murine cytomegalovirus (MCMV) express the regulatory cytokine interleukin (IL)-10. IL-10⁺CD4⁺ T cells co-expressed T_H1-associated transcription factors and chemokine receptors. Mice lacking T cell-derived IL-10 elicited enhanced antiviral T cell responses and restricted MCMV persistence in salivary glands and secretion in saliva. Thus, IL-10⁺CD4⁺ T cells suppress antiviral immune responses against CMV. Expansion of this T-cell population in the periphery was promoted by IL-27 whereas mucosal IL-10⁺ T cell responses were ICOS-dependent. Infected Il27rα-deficient mice with reduced peripheral IL-10⁺CD4⁺ T cell accumulation displayed robust T cell responses and restricted MCMV persistence and shedding. Temporal inhibition experiments revealed that IL-27R signaling during initial infection was required for the suppression of T cell immunity and control of virus shedding during MCMV persistence. IL-27 production was promoted by type-I IFN, suggesting that β-herpesviridae exploit the immune-regulatory properties of this antiviral pathway to establish chronicity. Further, our data reveal that cytokine signaling events during initial infection profoundly influence virus chronicity.

Viruses including the pathogenic β-herpesvirus human cytomegalovirus (HCMV) can replicate within and disseminate from mucosal tissues. Understanding how to improve antiviral immune responses to restrict virus replication in the mucosa could help counter virus transmission. Studies in the murine cytomegalovirus (MCMV) model have demonstrated the importance of the CD4⁺ T cells in control of mucosal MCMV replication. However, this process is inefficient, allowing virus persistence. Herein, we reveal that production by CD4⁺ T cells of the immune-suppressive soluble protein, or cytokine, interleukin (IL)-10 facilitates virus persistence in mucosal tissue. Mice deficient in T cell-derived IL-10 mounted heightened T cell responses and reduced virus replication in the salivary glands and shedding in the saliva. The cytokine IL-27 induced IL-10-producing CD4⁺ T cells in the periphery whereas a cell surface-expressed protein, ICOS, promoted mucosal IL-10⁺ T cell responses. IL-27 acted in the initial stages of infection to impinge on T cell responses and antiviral control. In turn, IL-27 production in response to viral infection was triggered by type-I interferon, a prototypic antiviral cytokine. Thus, our data suggest that herpesviruses may exploit immune-suppressive properties of this early antiviral cytokine response to facilitate persistence within and shedding from mucosal tissue.

IL-27 Directly Enhances Germinal Center B Cell Activity and Potentiates Lupus in Sanroque Mice

Germinal centers (GC) give rise to high-affinity and long-lived Abs and are critical in immunity and autoimmunity. IL-27 supports GCs by promoting survival and function of T follicular helper cells. We demonstrate that IL-27 also directly enhances GC B cell function. Exposure of naive human B cells to rIL-27 during in vitro activation enhanced their differentiation into CD20⁺CD38⁺CD27^lowCD95⁺CD10⁺ cells, consistent with the surface marker phenotype of GC B cells. This effect was inhibited by loss-of-function mutations in STAT1 but not STAT3 To extend these findings, we studied the in vivo effects of IL-27 signals to B cells in the GC-driven Roquin^san/san lupus mouse model. Il27ra^-/-Roquin^san/san mice exhibited significantly reduced GCs, IgG2a(c)⁺ autoantibodies, and nephritis. Mixed bone marrow chimeras confirmed that IL-27 acts through B cell- and CD4⁺ T cell-intrinsic mechanisms to support GCs and alter the production of pathogenic Ig isotypes. To our knowledge, our data provide the first evidence that IL-27 signals directly to B cells promote GCs and support the role of IL-27 in lupus.

Levels of Interleukin 27 and Interleukin 35 in the Serum and Vitreous of Patients with Proliferative Diabetic Retinopathy

PURPOSE

To examine the role of interleukin 27(IL-27) and interleukin 35 (IL-35) in diabetic retinopathy (DR).

METHODS

Patients with diabetes mellitus were divided into three groups: diabetes without retinopathy (DWR), non-proliferative diabetic retinopathy (NPDR), and proliferative diabetic retinopathy (PDR). Patients with idiopathic macular epiretinal membrane (IMEM) were included as a control group. The serum and vitreous levels of IL-27 and IL-35 were measured using ELISA.

RESULTS

The serum levels of IL-27 (median 240.900 pg/mL, range 42.224 - 617.810 pg/mL; p < 0.001) and IL-35 (median 11.875 ng/mL, range 8.640 - 19.340 ng/mL; p < 0.001) were significantly decreased in PDR patients compared to controls (median 2712.310 pg/mL, range 1005.375-5786.877 pg/mL and median 25.185 ng/mL, range 22.845 - 29.590 ng/mL, respectively). The vitreous levels of IL-35 were significantly decreased in PDR patients (16.32 ± 3.24 ng/mL) compared to controls (24.54 ± 5.86 ng/mL, p < 0.001).

CONCLUSIONS

Serum and vitreous levels of IL-35 and serum level of IL-27 may be associated with the pathogenesis of PDR.

Blockade of interleukin-27 signaling reduces GVHD in mice by augmenting Treg reconstitution and stabilizing Foxp3 expression

Reestablishment of competent regulatory pathways has emerged as a strategy to reduce the severity of graft-versus-host disease (GVHD), and recalibrate the effector and regulatory arms of the immune system. However, clinically feasible, cost-effective strategies that do not require extensive ex vivo cellular manipulation have remained elusive. In the current study, we demonstrate that inhibition of the interleukin-27p28 (IL-27p28) signaling pathway through antibody blockade or genetic ablation prevented lethal GVHD in multiple murine transplant models. Moreover, protection from GVHD was attributable to augmented global reconstitution of CD4⁺ natural regulatory T cells (nTregs), CD4⁺ induced Tregs (iTregs), and CD8⁺ iTregs, and was more potent than temporally concordant blockade of IL-6 signaling. Inhibition of IL-27p28 also enhanced the suppressive capacity of adoptively transferred CD4⁺ nTregs by increasing the stability of Foxp3 expression. Notably, blockade of IL-27p28 signaling reduced T-cell-derived-IL-10 production in conventional T cells; however, there was no corresponding effect in CD4⁺ or CD8⁺ Tregs, indicating that IL-27 inhibition had differential effects on IL-10 production and preserved a mechanistic pathway by which Tregs are known to suppress GVHD. Targeting of IL-27 therefore represents a novel strategy for the in vivo expansion of Tregs and subsequent prevention of GVHD without the requirement for ex vivo cellular manipulation, and provides additional support for the critical proinflammatory role that members of the IL-6 and IL-12 cytokine families play in GVHD biology.

Thymic DCs derived IL-27 regulates the final maturation of CD4(+) SP thymocytes

IL-27, as a pleiotropic cytokine, promotes the differentiation of naïve T cells to Th1, while suppressing Th2 and Th17 differentiation in the periphery. However, the role of IL-27 in the thymocyte development remains unknown. Here we showed that IL-27 was highly expressed in thymic plasmacytoid dendritic cells (pDCs) while its receptor expression was mainly detected in CD4⁺ single-positive (SP) thymocytes. Deletion of the p28 subunit in DCs resulted in a reduction of the most mature Qa-2⁺ subsets of CD4⁺ SP T cells. This defect was rescued by intrathymic administration of exogenous IL-27. In vitro differentiation assay further demonstrated that IL-27 alone was able to drive the maturation of the newly generated 6C10⁺CD69⁺CD4⁺ SP cells into Qa-2⁺ cells. Collectively, this study has revealed an important role of thymic DCs-derived IL-27 in the regulation of the phenotypic maturation of CD4⁺ SP thymocytes.

Promotion of Expansion and Differentiation of Hematopoietic Stem Cells by Interleukin-27 into Myeloid Progenitors to Control Infection in Emergency Myelopoiesis

Emergency myelopoiesis is inflammation-induced hematopoiesis to replenish myeloid cells in the periphery, which is critical to control the infection with pathogens. Previously, pro-inflammatory cytokines such as interferon (IFN)-α and IFN-γ were demonstrated to play a critical role in the expansion of hematopoietic stem cells (HSCs) and myeloid progenitors, leading to production of mature myeloid cells, although their inhibitory effects on hematopoiesis were also reported. Therefore, the molecular mechanism of emergency myelopoiesis during infection remains incompletely understood. Here, we clarify that one of the interleukin (IL)-6/IL-12 family cytokines, IL-27, plays an important role in the emergency myelopoiesis. Among various types of hematopoietic cells in bone marrow, IL-27 predominantly and continuously promoted the expansion of only Lineage⁻Sca-1⁺c-Kit⁺ (LSK) cells, especially long-term repopulating HSCs and myeloid-restricted progenitor cells with long-term repopulating activity, and the differentiation into myeloid progenitors in synergy with stem cell factor. These progenitors expressed myeloid transcription factors such as Spi1, Gfi1, and Cebpa/b through activation of signal transducer and activator of transcription 1 and 3, and had enhanced potential to differentiate into migratory dendritic cells (DCs), neutrophils, and mast cells, and less so into macrophages, and basophils, but not into plasmacytoid DCs, conventional DCs, T cells, and B cells. Among various cytokines, IL-27 in synergy with the stem cell factor had the strongest ability to augment the expansion of LSK cells and their differentiation into myeloid progenitors retaining the LSK phenotype over a long period of time. The experiments using mice deficient for one of IL-27 receptor subunits, WSX-1, and IFN-γ revealed that the blood stage of malaria infection enhanced IL-27 expression through IFN-γ production, and the IL-27 then promoted the expansion of LSK cells, differentiating and mobilizing them into spleen, resulting in enhanced production of neutrophils to control the infection. Thus, IL-27 is one of the limited unique cytokines directly acting on HSCs to promote differentiation into myeloid progenitors during emergency myelopoiesis.

Emergency myelopoiesis is inflammation-induced hematopoiesis that is critical for controlling infection with pathogens, but the molecular mechanism remains incompletely understood. Here, we clarify that one of the interleukin (IL)-6/IL-12 family cytokines, IL-27, plays an important role in emergency myelopoiesis. Among various types of hematopoietic cells in bone marrow, IL-27 predominantly and continuously promoted expansion of only Lineage⁻Sca-1⁺c-Kit⁺ (LSK) cells, especially long-term repopulating hematopoietic stem cells, and differentiation into myeloid progenitors in synergy with stem cell factor. These progenitors expressed myeloid transcription factors such as Spi1, Gfi1, and Cebpa/b through activation of signal transducer and activator of transcription 1 and 3, and had enhanced potential to differentiate into neutrophils, but not into plasmacytoid dendritic cells. Among various cytokines, IL-27 in synergy with stem cell factor had the strongest ability to augment the expansion of LSK cells and their differentiation into myeloid progenitors. The blood stage of malaria infection was revealed to enhance IL-27 expression through interferon-γ production, and IL-27 then promoted the expansion of LSK cells, differentiating and mobilizing them into the spleen, resulting in enhanced production of neutrophils to control the infection. Thus, IL-27 is one of the limited unique cytokines directly acting on hematopoietic stem cells to promote differentiation into myeloid progenitors during emergency myelopoiesis.

The role of IL-17 signaling in regulation of the liver-brain axis and intestinal permeability in Alcoholic Liver Disease

Alcoholic liver disease (ALD) progresses from a normal liver, to steatosis, steatohepatitis, fibrosis and hepatocellular carcinoma (HCC). Despite intensive studies, the pathogenesis of ALD is poorly understood, in part due to a lack of suitable animal models which mimic the stages of ALD progression. Furthermore, the role of IL-17 in ALD has not been evaluated. We and others have recently demonstrated that IL-17 signaling plays a critical role in development of liver fibrosis and cancer. Here we summarize the most recent evidence supporting the role of IL-17 in ALD. As a result of a collaborative effort of Drs. Karin, Gao, Tsukamoto and Kisseleva, we developed several improved models of ALD in mice: 1) chronic-plus-binge model that mimics early stages of steatohepatitis, 2) intragastric ethanol feeding model that mimics alcoholic steatohepatitis and fibrosis, and 3) diethylnitrosamine (DEN)+alcohol model that mimics alcoholic liver cancer. These models might provide new insights into the mechanism of IL-17 signaling in ALD and help identify novel therapeutic targets.

An IL-27/Lag3 axis enhances Foxp3+ regulatory T cell-suppressive function and therapeutic efficacy

Foxp3-expressing regulatory T cells (Tregs) are central regulators of immune homeostasis and tolerance. As it has been suggested that proper Treg function is compromised under inflammatory conditions, seeking for a pathway that enhances or stabilizes Treg function is a subject of considerable interest. We report that interleukin (IL)-27, an IL-12 family cytokine known to have both pro- and anti-inflammatory roles in T cells, plays a pivotal role in enhancing Treg function to control T cell-induced colitis, a model for inflammatory bowel disease (IBD) in humans. Unlike wild-type (WT) Tregs capable of inhibiting colitogenic T-cell expansion and inflammatory cytokine expression, IL-27R-deficient Tregs were unable to downregulate inflammatory T-cell responses. Tregs stimulated with IL-27 expressed substantially improved suppressive function in vitro and in vivo. IL-27 stimulation of Tregs induced expression of Lag3, a surface molecule implicated in negatively regulating immune responses. Lag3 expression in Tregs was critical to mediate Treg function in suppressing colitogenic responses. Human Tregs also displayed enhanced suppressive function and Lag3 expression following IL-27 stimulation. Collectively, these results highlight a novel function for the IL-27/Lag3 axis in modulating Treg regulation of inflammatory responses in the intestine.

New Approaches to the Immunotherapy of Type 1 Diabetes Mellitus Using Interleukin-27

Type 1 diabetes (T1D) is a pancreatic beta cell specific autoimmune disease. One of the most significant current discussions in T1D studies is therapy. Since the conventional therapy, islet transplantation and external insulin, e.g., cannot prevent the destructive autoimmune process against original beta cells and persistent hyperglycemia remains, so recent developments in the field of T1D therapy paved the way to a renewed interest in immunotherapy based on the disease process, especially monoclonal antibody therapy. Due to encouraging laboratory results, cytokine antibody-based drugs could be effective in the clinical direction of the T1D disease process. Hence, implementation of this approach can be useful to improve clinical and laboratory manifestations of T1D.

IL-27-induced modulation of autoimmunity and its therapeutic potential

Interleukin-27 (IL-27) is a new member of the IL-12 family. It is produced by activated antigen-presenting cells and plays an important role in the regulation of CD4+ T cell differentiation and immune response. IL-27 activates multiple signaling cascades, including the JAK-STAT and p38 MAPK pathways. Several studies have revealed that IL-27 promotes the differentiation of Th1 and Tr1, but inhibits Th2, Th17, and Treg cells. However, a few studies have shown an opposite effect on certain T cell subsets, such as Treg. IL-27 displays both pro- and anti- inflammatory activities in different autoimmune diseases. Here, we have discussed the role of IL-27 in rheumatoid arthritis, multiple sclerosis, colitis, lupus, psoriasis, type 1 diabetes, and uveitis. Most of this information is derived from experimental models of these autoimmune diseases. The mechanistic basis of the dual role of IL-27 in inflammation and autoimmunity is still not fully defined. In general, the pro-/anti-inflammatory activity of IL-27 is influenced by the underlying immune effector pathways, the phase of the disease, the presence or absence of counter-regulatory cytokines/T cell subsets, and the tissue/cell type under study. Despite a spectrum of outcomes in various autoimmune diseases, mostly anti-inflammatory and immunomodulatory effects of IL-27 have been observed in this category of diseases. Accordingly, IL-27 represents a novel, promising target/agent for the treatment of autoimmune diseases.

The Yin and Yang aspects of IL-27 in induction of cancer-specific T-cell responses and immunotherapy

Accumulating evidences from animal studies have indicated that both endogenous and exogenous IL-27, an IL-12 family of cytokine, can increase antitumor T-cell activities and inhibit tumor growth. IL-27 can modulate Treg responses, and program effector T cells into a unique T-effector stem cell (TSEC) phenotype, which enhances T-cell survival in the tumor microenvironment. However, animal studies also suggest that IL-27 induces molecular pathways such as IL-10, PD-L1 and CD39, which may downregulate tumor-specific T-cell responses. In this review paper, we will discuss the Yin and Yang aspects of IL-27 in the induction of tumor-specific T-cell responses, and the potential impacts of these functions of IL-27 in the design of cancer immunotherapy.

Interleukin-27 ameliorates coxsackievirus-B3-induced viral myocarditis by inhibiting Th17 cells

Background

Interleukin (IL)-27, which has both pro and anti- inflammatory properties, is a new discovered heterodimeric cytokine that belongs to IL-12 family. However, the expression pattern and functional role of IL-27 in viral myocarditis (VMC) has not been investigated.

Methods

BALB/c mice were intraperitoneally (i.p) infected with Coxsackie virus B3 (CVB3) for establishing VMC models. Mice were then injected i.p. with Anti-Mouse IL-27 p28Ab or recombinant IL-27 for neutralization and overexpression of IL-27. The survival rates of mice were recorded and the kinetics of IL-27 expression, the frequencies of Th17 cells and the expression of inflammatory cytokine in CVB3-infected mice were determined by ELISA, real-time PCR and flow cytometry.

Results

The IL-27 expression in heart tissues and serum in coxsackievirus B3 (CVB3)-induced myocarditis mice peaked on day 4 but then rapidly decreased during the late infectious stage of CVB3, high IL-27 levels were negatively correlated with bodyweight loss (r = −0.71, P = 0.021) and myocardial pathological score (r = −0.85, P = 0.0018). Additionally, neutralization of IL-27 with Anti-IL-27 Ab accelerated, whereas systemic administration of recombinant mouse IL-27 ameliorated CVB3-induced myocarditis. The protective role of IL-27 in VMC was reflected by an improved survival rate, increased bodyweights, and reduced pathological scores in Anti-IL-27 group compared with IgG control group. Mechanistic investigations showed that IL-27 inhibited Th17 cells frequencies and IL-17 production, as well as the Th17-related proinflammatory cytokines in heart tissues.

Conclusions

Our results demonstrate that that IL-27 effectively protects the myocardium from the pathogenesis of CVB3 induced myocarditis, which may be attributable to reduced Th17 production. IL-27 might serve as a novel therapeutic treatment for VMC.

Electronic supplementary material

The online version of this article (doi:10.1186/s12985-015-0418-x) contains supplementary material, which is available to authorized users.

Parasite-Specific CD4+ IFN-γ+ IL-10+ T Cells Distribute within Both Lymphoid and Nonlymphoid Compartments and Are Controlled Systemically by Interleukin-27 and ICOS during Blood-Stage Malaria Infection

Immune-mediated pathology in interleukin-10 (IL-10)-deficient mice during blood-stage malaria infection typically manifests in nonlymphoid organs, such as the liver and lung. Thus, it is critical to define the cellular sources of IL-10 in these sensitive nonlymphoid compartments during infection. Moreover, it is important to determine if IL-10 production is controlled through conserved or disparate molecular programs in distinct anatomical locations during malaria infection, as this may enable spatiotemporal tuning of the regulatory immune response. In this study, using dual gamma interferon (IFN-γ)–yellow fluorescent protein (YFP) and IL-10–green fluorescent protein (GFP) reporter mice, we show that CD4⁺ YFP⁺ T cells are the major source of IL-10 in both lymphoid and nonlymphoid compartments throughout the course of blood-stage Plasmodium yoelii infection. Mature splenic CD4⁺ YFP⁺ GFP⁺ T cells, which preferentially expressed high levels of CCR5, were capable of migrating to and seeding the nonlymphoid tissues, indicating that the systemically distributed host-protective cells have a common developmental history. Despite exhibiting comparable phenotypes, CD4⁺ YFP⁺ GFP⁺ T cells from the liver and lung produced significantly larger quantities of IL-10 than their splenic counterparts, showing that the CD4⁺ YFP⁺ GFP⁺ T cells exert graded functions in distinct tissue locations during infection. Unexpectedly, given the unique environmental conditions within discrete nonlymphoid and lymphoid organs, we show that IL-10 production by CD4⁺ YFP⁺ T cells is controlled systemically during malaria infection through IL-27 receptor signaling that is supported after CD4⁺ T cell priming by ICOS signaling. The results in this study substantially improve our understanding of the systemic IL-10 response to malaria infection, particularly within sensitive nonlymphoid organs.

IL-Y, a synthetic member of the IL-12 cytokine family, suppresses the development of type 1 diabetes in NOD mice

The IL-12 family of heterodimeric cytokines, consisting of IL-12, IL-23, IL-27, and IL-35, has important roles in regulating the immune response. IL-12 family members are comprised of a heterodimer consisting of α and β chains: IL-12 (p40 and p35), IL-23 (p40 and p19), IL-27 (Ebi3 and p28), and IL-35 (Ebi3 and p35). Given the combinatorial nature of the IL-12 family, we generated adenoviral vectors expressing two putative IL-12 family members not yet found naturally, termed IL-X (Ebi3 and p19) and IL-Y (p40 and p28), as single-chain molecules. Single chain IL-Y (scIL-Y), but not scIL-X, was able to stimulate significantly a unique cytokine/chemokine expression profile as well as activate STAT3 in mice, in part, through a pathway involving IL-27Rα in splenocytes. Adenoviral-mediated, intratumoral delivery of scIL-Y increased tumor growth in contrast to the anti-tumor effects of scIL-12 and scIL-23. Similarly, treatment of prediabetic NOD mice by intravenous injection of Ad.scIL-Y prevented the onset of hyperglycemia. Analysis of cells from Ad.scIL-Y-treated NOD mice demonstrated that scIL-Y reduced expression of inflammatory mediators such as IFN-γ. Our data demonstrate that a novel, synthetic member of the IL-12 family, termed IL-Y, confers unique immunosuppressive effects in two different disease models and thus could have therapeutic applications.

Interleukin 35: Critical regulator of immunity and lymphocyte-mediated diseases

Cytokines coordinate the activities of innate and adaptive immune systems and the Interleukin 12 (IL-12) family of cytokines has emerged as critical regulators of immunity in infectious and autoimmune diseases. While some members (IL-12 and IL-23) are associated with the pathogenesis of chronic inflammatory diseases, others (IL-27 and IL-35) mitigate autoimmune diseases. Unlike IL-12, IL-23 and IL-27 that are produced mainly by antigen presenting cells, IL-35 is predominantly secreted by regulatory B (i35-Bregs) and T (iTR35) cells. The discovery that IL-35 can induce the conversion or expansion of lymphocytes to regulatory B and T cells has considerable implications for therapeutic use of autologous regulatory B and T cells in human diseases. Although our current understanding of the immunobiology of IL-35 or its subunits (p35 and Ebi3) is still rudimentary, our goal in this review is to summarize what we know about this enigmatic cytokine and its potential clinical use, particularly in the treatment of CNS autoimmune diseases.

Polymorphisms and plasma levels of IL-27: impact on genetic susceptibility and clinical outcome of bladder cancer

Background

Interleukin-27 (IL-27) has been recognized as a pleiotropic cytokine with both pro- and anti-inflammatory properties. Few studies have investigated polymorphisms and serum/plasma levels of IL-27 in diseases including cancers. This study has analyzed the associations of IL-27 gene polymorphisms, as well as plasma levels of IL-27, with susceptibility to bladder cancer and clinical outcome.

Methods

Three hundred and thirty-two patients (nonmuscle-invasive bladder cancer (NMIBC)/muscle-invasive bladder cancer (MIBC): 176/156) included in a 60-month follow-up program and 499 controls were enrolled. Two single nucleotide polymorphisms (SNPs), rs153109 and rs17855750, were genotyped by polymerase chain reaction (PCR) -restriction fragment length polymorphism (RFLP) method. Plasma concentration of IL-27 was determined by ELISA in 124 patients (NMIBC/MIBC: 50/74) and 151 controls.

Results

Significantly increased risk for bladder cancer was associated with AG/GG genotypes of rs153109 (P = 0.029). No GG genotype of rs17855750 was observed in controls, while 4 patients were found to be GG homozygotes, suggesting GG genotype may be associated with bladder cancer risk (P = 0.006). For bladder cancer patients, SNP rs17855750 was also associated with increased risk for MIBC. For MIBC patients, but not NMIBC, TG/GG genotypes of rs17855750 turned out to be a protective factor for overall survival (P = 0.035). Significantly reduced plasma levels of IL-27 were observed in both NMIBC and MIBC patients compared with controls (P < 0.0001).

Conclusion

Our data suggest that polymorphisms and reduced plasma levels of IL-27 may predict the susceptibility to bladder cancer, and rs17855750 may be a useful marker to distinguish patients with high risk of death.

Immunoendocrine dysbalance during uncontrolled T. cruzi infection is associated with the acquisition of a Th-1-like phenotype by Foxp3(+) T cells

We previously showed that Trypanosomacruzi infection in C57BL/6 mice results in a lethal infection linked to unbalanced pro- and anti-inflammatory mediators production. Here, we examined the dynamics of CD4(+)Foxp3(+) regulatory T (Treg) cells within this inflammatory and highly Th1-polarized environment. Treg cells showed a reduced proliferation rate and their frequency is progressively reduced along infection compared to effector T (Teff) cells. Also, a higher fraction of Treg cells showed a naïve phenotype, meanwhile Teff cells were mostly of the effector memory type. T. cruzi infection was associated with the production of pro- and anti-inflammatory cytokines, notably IL-27p28, and with the induction of T-bet and IFN-γ expression in Treg cells. Furthermore, endogenous glucocorticoids released in response to T. cruzi-driven immune activation were crucial to sustain the Treg/Teff cell balance. Notably, IL-2 plus dexamethasone combined treatment before infection was associated with increased Treg cell proliferation and expression of GATA-3, IL-4 and IL-10, and increased mice survival time. Overall, our results indicate that therapies aimed at specifically boosting Treg cells, which during T. cruzi infection are overwhelmed by the effector immune response, represent new opportunities for the treatment of Chagas disease, which is actually only based on parasite-targeted chemotherapy.

Biology of IL-27 and its role in the host immunity against Mycobacterium tuberculosis

IL-27, a heterodimeric cytokine of IL-12 family, regulates both innate and adaptive immunity largely via Jak-Stat signaling. IL-27 can induce IFN-γ and inflammatory mediators from T lymphocytes and innate immune cells. IL-27 has unique anti-inflammatory properties via both Tr1 cells dependent and independent mechanisms. Here the role and biology of IL-27 in innate and adaptive immunity are summarized, with special interest with immunity against Mycobacterium tuberculosis.

Interleukin 27 polymorphisms in HCV RNA positive patients: is there an impact on response to interferon therapy?

Background

Interleukin 27 (IL-27) has pleiotropic properties that can either limit or enhance immune responses. Recent studies revealed that single nucleotide polymorphisms (SNPs) of the IL-27 promoter region modulate the development of infectious diseases and individual's susceptibility to therapeutic response. Little is known about the relationship between IL-27 single nucleotide polymorphisms and therapy response in patients infected by hepatitis C virus (HCV). In this study we have investigated the potential role of SNPs in the promoter region of IL27 p28 gene (alleles rs153109) on the outcome of HCV infected patients.

Methods

rs153109, corresponding to position c.-964A>G of the IL-27 locus, was amplified from genomic DNA extracted from 15 patients with chronic hepatitis C stratified by sustained viral response (SVR), relapser and non-responder, after treatment with peginterferon-α (PegIFN- α) combined with ribavirin (RBV). Amplification products were studied by direct sequencing.

Results

This method has been applied in a preliminary study on patients with chronic hepatitis C to provide information for a standardized assay useful to genotyping of rs153109 SNPs of IL-27p28. The genotype distribution of the c.-964 A>G polymorphism was more present in patients who did not achieve a SVR. By contrast, the genotype G/G was absent in non-responder and relapser patients. Moreover, the analysis of allelic distribution of rs153109 highlighted a predominance of allele A in all genotypes in spite of allele G.

Conclusions

Our work provides preliminary information for a standardized method potentially useful for genotyping rs153109, and suggests its utility as a candidate approach to evaluate IL-27 p28 polymorphisms as additional clinical predictors of response to therapies in HCV infected patients.

Tr-1-like CD4+CD25-CD127-/lowFOXP3- cells are the main source of interleukin 10 in patients with cutaneous leishmaniasis due to Leishmania braziliensis

CD4(+)CD25(+)FOXP3(+) regulatory T cells have long been shown to mediate susceptibility to Leishmania infection, mainly via interleukin 10 production. In this work, we showed that the main sources of interleukin 10 in peripheral blood mononuclear cells (PBMCs) from patients with cutaneous leishmaniasis due to Leishmania braziliensis are CD4(+)CD25(-)CD127(-/low)FOXP3(-) cells. Compared with uninfected controls, patients with CL had increased frequencies of circulating interleukin 10-producing CD4(+)CD25(-)CD127(-/low) cells, which efficiently suppressed tumor necrosis factor α production by the total PBMC population. Also, in CL lesions, interleukin 10 was mainly produced by CD4(+)CD25(-) cells, and interleukin 10 messenger RNA expression was associated with interleukin 27, interleukin 21, and interferon γ expression, rather than with FOXP3 or transforming growth factor β expressions. Active production of both interleukin 27 and interleukin 21, together with production of interferon γ and interleukin 10, was also detected in the lesions. Since these cytokines are associated with the differentiation and activity of Tr-1 cells, our results suggest that this cell population may play an important role in the immunomodulation of CL. Therefore, development of treatments that interfere with this pathway may lead to faster parasite elimination.

Cellular factors targeting APCs to modulate adaptive T cell immunity

The fate of adaptive T cell immunity is determined by multiple cellular and molecular factors, among which the cytokine milieu plays the most important role in this process. Depending on the cytokines present during the initial T cell activation, T cells become effector cells that produce different effector molecules and execute adaptive immune functions. Studies thus far have primarily focused on defining how these factors control T cell differentiation by targeting T cells themselves. However, other non-T cells, particularly APCs, also express receptors for the factors and are capable of responding to them. In this review, we will discuss how APCs, by responding to those cytokines, influence T cell differentiation and adaptive immunity.

Protection and pathology during parasite infection: IL-10 strikes the balance

The host response to infection requires an immune response to be strong enough to control the pathogen but also restrained, to minimize immune-mediated pathology. The conflicting pressures of immune activation and immune suppression are particularly apparent in parasite infections, where co-evolution of host and pathogen has selected many different compromises between protection and pathology. Cytokine signals are critical determinants of both protective immunity and immunopathology, and, in this review, we focus on the regulatory cytokine IL-10 and its role in protozoan and helminth infections. We discuss the sources and targets of IL-10 during parasite infection, the signals that initiate and reinforce its action, and its impact on the invading parasite, on the host tissue, and on coincident immune responses.

IL-27 limits central nervous system viral clearance by promoting IL-10 and enhances demyelination

IL-27 is a pleiotropic member of the IL-6 and IL-12 cytokine family composed of the IL-27p28 and the EBV-induced gene 3. IL-27 and its receptor mRNA are both upregulated in the CNS during acute encephalomyelitis induced by the JHM strain of mouse hepatitis virus (JHMV) and sustained during viral persistence. Contributions of IL-27 to viral pathogenesis were evaluated by infection of IL-27Rα-chain-deficient (IL-27Rα(-/-)) mice. The absence of IL-27 signaling accelerated virus control within the CNS associated with increased IFN-γ secreting virus-specific CD4+ and CD8+ T cells. Abrogation of IL-27 signaling did not affect virus-specific CD8+ T cell-mediated IL-10 production or cytolytic activity or Foxp3+ regulatory T cell populations. However, IL-10 production by virus-specific CD4+ T cells was reduced significantly. Despite increased T cell-mediated antiviral function in IL-27Rα(-/-) mice, the virus persisted in the CNS at similar levels as in wild-type mice. Nevertheless, IL-27Rα(-/-) mice exhibited decreased clinical disease during persistence, coincident with less severe demyelination, the hallmark tissue damage associated with JHMV infection. Overall, these data demonstrate that in contrast to viral infections at other sites, IL-27 does not play a proinflammatory role during JHMV-induced encephalomyelitis. Rather, it limits CNS inflammation and impairs control of CNS virus replication via induction of IL-10 in virus-specific CD4+ T cells. Furthermore, in contrast to its protective role in limiting CNS autoimmunity and preventing immunopathology, these data define a detrimental role of IL-27 in promoting demyelination by delaying viral control.

IL-27, targeting antigen-presenting cells, promotes Th17 differentiation and colitis in mice

T helper type 17 (Th17) cells have been implicated in autoimmunity and inflammatory bowel disease (IBD). Antigen-presenting cell (APC) -derived cytokines such as interleukin (IL)-1β and IL-6 are key mediators supporting Th17 differentiation, yet how these factors are induced in vivo remains unclear. Here, we show that IL-27 acting on APCs enhances IL-6 and IL-1β production and Th17 differentiation. IL-27Rα-/- T-cell receptor (TCR)β-/- recipients fail to develop gut inflammation following naive CD4 T-cell transfer, whereas IL-27Rα+/+ TCRβ-/- recipients develop severe colitis. Investigation of T-cell responses exhibits that IL-27Rα-/- TCRβ-/- mice do not support Th17 differentiation with significantly decreased levels of IL-6 and IL-1β by APCs. Our study has identified a novel proinflammatory role for IL-27 in vivo that promotes Th17 differentiation by inducing Th17-supporting cytokines in APCs.

A soluble form of IL-27Rα is a natural IL-27 antagonist

IL-27 is a cytokine of the IL-12 family that plays a key role in the regulation of inflammatory and T cell responses. Its receptor is composed of IL-27Rα and gp130 and activates the STAT pathway. We show in this study, using an ELISA that we developed, that a naturally occurring soluble form of IL-27Rα (sIL-27Rα) is produced by human activated CD4(+) and CD8(+) T cells, B cells, myeloid cells, and various cell lines. sIL-27Rα is present at a mean concentration of 10,344 ± 1,274 pg/ml in the sera from healthy individuals. Biochemical studies showed that sIL-27Rα is released as two N-glycosylated variants of ∼ 90 and ∼ 70 kDa. In IL-27Rα-transfected COS7 cells, primary cells, and cell lines, production of sIL-27Rα is inhibited by the metalloprotease inhibitors GM6001 and TAPI-0. Importantly, natural sIL-27Rα binds rIL-27, inhibits IL-27 binding to its cell surface receptor, and is a potent inhibitor of IL-27 signaling, as shown by its ability to specifically block IL-27-mediated STAT activation, at low molar excess over IL-27. Also, we found that serum levels of sIL-27Rα were elevated in patients with Crohn's disease, a Th1-mediated disease. These findings suggest that sIL-27Rα may play important immunoregulatory functions under normal and pathological conditions.

Contribution of IL-12/IL-35 common subunit p35 to maintaining the testicular immune privilege

The testis is an organ with immune privilege. The comprehensive blood–testis barrier formed by Sertoli cells protects autoimmunogenic spermatozoa and spermatids from attack by the body’s immune system. The interleukin (IL)-6/IL-12 family cytokines IL-12 (p35/p40), IL-23 (p19/p40), IL-27 (p28/Epstein-Barr virus−induced gene 3 [EBI3]), and IL-35 (p35/EBI3) play critical roles in the regulation of various immune responses, but their roles in testicular immune privilege are not well understood. In the present study, we investigated whether these cytokines are expressed in the testes and whether they function in the testicular immune privilege by using mice deficient in their subunits. Expression of EBI3 was markedly increased at both mRNA and protein levels in the testes of 10- or 12-week-old wild-type mice as compared with levels in 2-week-old mice, whereas the mRNA expression of p40 was markedly decreased and that of p35 was conserved between these two groups. Lack of EBI3, p35, and IL-12 receptor β2 caused enhanced infiltration of lymphocytes into the testicular interstitium, with increased interferon-γ expression in the testes and autoantibody production against mainly acrosomal regions of spermatids. Spermatogenic disturbance was more frequently observed in the seminiferous tubules, especially when surrounded by infiltrating lymphocytes, of these deficient mice than in those of wild-type mice. In particular, p35-deficient mice showed the most severe spermatogenic disturbance. Immunohistochemical analyses revealed that endothelial cells and peritubular cells in the interstitium were highly positive for p35 at both ages, and CD163⁺ resident macrophages positive for p35 and EBI3, possibly producing IL-35, were also detected in the interstitium of 12-week-old mice but not those of 2-week-old mice. These results suggest that p35 helps in maintaining the testicular immune privilege, in part in an IL-35-dependent manner.

Mathematical modeling of interleukin-27 induction of anti-tumor T cells response

Interleukin-12 is a pro-inflammatory cytokine which promotes Th1 and cytotoxic T lymphocyte activities, such as Interferon- secretion. For this reason Interleukin-12 could be a powerful therapeutic agent for cancer treatment. However, Interleukin-12 is also excessively toxic. Interleukin-27 is an immunoregulatory cytokine from the Interleukin-12 family, but it is not as toxic as Interleukin-12. In recent years, Interleukin-27 has been considered as a potential anti-tumor agent. Recent experiments in vitro and in vivo have shown that cancer cells transfected with IL-27 activate CD8⁺ T cells to promote the secretion of anti-tumor cytokines Interleukin-10, although, at the same time, IL-27 inhibits the secretion of Interferon- by CD8⁺ T cells. In the present paper we develop a mathematical model based on these experimental results. The model involves a dynamic network which includes tumor cells, CD8⁺ T cells and cytokines Interleukin-27, Interleukin-10 and Interferon-. Simulations of the model show how Interleukin-27 promotes CD8⁺ T cells to secrete Interleukin-10 to inhibit tumor growth. On the other hand Interleukin-27 inhibits the secretion of Interferon- by CD8⁺ T cells which somewhat diminishes the inhibition of tumor growth. Our numerical results are in qualitative agreement with experimental data. We use the model to design protocols of IL-27 injections for the treatment of cancer and find that, for some special types of cancer, with a fixed total amount of drug, within a certain range, continuous injection has better efficacy than intermittent injections in reducing the tumor load while the treatment is ongoing, although the decrease in tumor load is only temporary.

Interleukin-35: A Novel Mediator of Peripheral Tolerance

Interleukin-35 is a potent suppressive cytokine of the IL-12 family. Although other members of the IL-12 family are produced mainly by antigen-presenting cells (APCs), IL-35 is produced by regulatory T (Treg) cells and suppresses cell proliferation. It has been shown to play an important role in many disease models and has been recently shown to have additional functions aside from inhibition of proliferation, including inducing its own expression in non-Treg cells. In this chapter, we discuss the history and current status of IL-35 biology, as well as suggest where the field might move in the future.

WSX-1 signalling inhibits CD4⁺ T cell migration to the liver during malaria infection by repressing chemokine-independent pathways

IL-27 is an important and non-redundant regulator of effector T cell accumulation in non-lymphoid tissues during infection. Using malaria as a model systemic pro-inflammatory infection, we demonstrate that the aberrant accumulation of CD4⁺ T cells in the liver of infected IL27R(-/-) (WSX-1(-/-)) mice is a result of differences in cellular recruitment, rather than changes in T cell proliferation or cell death. We show that IL-27 both inhibits the migratory capacity of infection-derived CD4⁺ T cells towards infection-derived liver cells, but also suppresses the production of soluble liver-derived mediator(s) that direct CD4⁺ T cell movement towards the inflamed tissue. Although CCL4 and CCL5 expression was higher in livers of infected WSX-1(-/-) mice than infected WT mice, and hepatic CD4⁺ T cells from WSX-1(-/-) mice expressed higher levels of CCR5 than cells from WT mice, migration of CD4⁺ T cells to the liver of WSX-1(-/-) mice during infection was not controlled by chemokine (R) signalling. However, anti-IL-12p40 treatment reduced migration of CD4⁺ T cells towards infection-derived liver cells, primarily by abrogating the hepatotropic migratory capacity of T cells, rather than diminishing soluble tissue-derived migratory signals. These results indicate that IL-27R signalling restricts CD4⁺ T cell accumulation within the liver during infection primarily by suppressing T cell chemotaxis, which may be linked to its capacity to repress Th1 differentiation, as well as by inhibiting the production of soluble, tissue-derived chemotaxins.

Regulation of immunopathogenesis during Plasmodium and Toxoplasma infections: more parallels than distinctions?

Toxoplasma and Plasmodium parasites exact a significant toll on public health. Host immunity required for efficient control of infection by these Apicomplexans involves the induction of potent T cell responses, which sometimes results in immunopathological damage. Thus, protective immune responses must be balanced by regulatory networks that limit immunopathology. We review several key cellular and molecular immunoregulatory networks operational during Toxoplasma and Plasmodium infections. Accumulating data show that despite differences in how the immune response controls these parasites, many host immunoregulatory pathways and cellular networks are common to both. Thus, understanding the cellular and molecular circuits that prevent or regulate immunopathological responses against one parasite is likely to inform our understanding of the host response to the other parasite.

Do Natural T Regulatory Cells become Activated to Antigen Specific T Regulatory Cells in Transplantation and in Autoimmunity?

Antigen specific T regulatory cells (T_reg) are often CD4⁺CD25⁺FoxP3⁺ T cells, with a phenotype similar to natural T_reg (nT_reg). It is assumed that nT_reg cannot develop into an antigen specific T_reg as repeated culture with IL-2 and a specific antigen does not increase the capacity or potency of nT_reg to promote immune tolerance or suppress in vitro. This has led to an assumption that antigen specific T_reg mainly develop from CD4⁺CD25⁻FoxP3⁻ T cells, by activation with antigen and TGF-β in the absence of inflammatory cytokines such as IL-6 and IL-1β. Our studies on antigen specific CD4⁺CD25⁺ T cells from animals with tolerance to an allograft, identified that the antigen specific and T_reg are dividing, and need continuous stimulation with specific antigen T cell derived cytokines. We identified that a variety of cytokines, especially IL-5 and IFN-γ but not IL-2 or IL-4 promoted survival of antigen specific CD4⁺CD25⁺FoxP3⁺ T_reg. To examine if nT_reg could be activated to antigen specific T_reg, we activated nT_reg in culture with either IL-2 or IL-4. Within 3 days, antigen specific T_reg are activated and there is induction of new cytokine receptors on these cells. Specifically nT_reg activated by IL-2 and antigen express the interferon-γ receptor (IFNGR) and IL-12p70 (IL-12Rβ2) receptor but not the IL-5 receptor (IL-5Rα). These cells were responsive to IFN-γ or IL-12p70. nT_reg activated by IL-4 and alloantigen express IL-5Rα not IFNGR or IL-12p70Rβ2 and become responsive to IL-5. These early activated antigen specific T_reg, were respectively named Ts1 and Ts2 cells, as they depend on Th1 or Th2 responses. Further culture of Ts1 cells with IL-12p70 induced Th1-like T_reg, expressing IFN-γ, and T-bet as well as FoxP3. Our studies suggest that activation of nT_reg with Th1 or Th2 responses induced separate lineages of antigen specific T_reg, that are dependent on late Th1 and Th2 cytokines, not the early cytokines IL-2 and IL-4.

Modulation of inflammation by interleukin-27

A growing body of evidence suggests an essential role of the heterodimeric cytokine, IL-27, for regulating immunity. IL-27 is composed of two subunits (p28 and EBI3) and is classified as a member of the IL-12 family of cytokines. APCs have been recognized as a major cellular source of IL-27 following activation with microbial products or IFNs (types I and II). In this review, we describe the current knowledge of the implications of IL-27 during the pathogenesis of infectious and autoimmune diseases. Experimental studies have used genetically targeted IL-27RA-/- mice, EBI3-/- mice, and p28-/- mice or involved study designs with administration of bioengineered IL-27/IL-27RA homologs. Whereas many reports have described that IL-27 suppresses inflammation, we also review the current literature, suggesting promotion of inflammation by IL-27 in some settings. Recent advances have also been made in understanding the cross-talk of cleavage products of the complement system with IL-27-mediated immune responses. Additional data on IL-27 have been obtained recently by observational studies in human patients with acute and chronic inflammatory diseases. Collectively, the findings from the past decade identify IL-27 as a critical immunoregulatory cytokine, especially for T cells, whereas some controversy is fueled by results challenging the view of IL-27 as a classical silencer of inflammation.

IL-27 receptor signalling restricts the formation of pathogenic, terminally differentiated Th1 cells during malaria infection by repressing IL-12 dependent signals

The IL-27R, WSX-1, is required to limit IFN-γ production by effector CD4⁺ T cells in a number of different inflammatory conditions but the molecular basis of WSX-1-mediated regulation of Th1 responses in vivo during infection has not been investigated in detail. In this study we demonstrate that WSX-1 signalling suppresses the development of pathogenic, terminally differentiated (KLRG-1⁺) Th1 cells during malaria infection and establishes a restrictive threshold to constrain the emergent Th1 response. Importantly, we show that WSX-1 regulates cell-intrinsic responsiveness to IL-12 and IL-2, but the fate of the effector CD4⁺ T cell pool during malaria infection is controlled primarily through IL-12 dependent signals. Finally, we show that WSX-1 regulates Th1 cell terminal differentiation during malaria infection through IL-10 and Foxp3 independent mechanisms; the kinetics and magnitude of the Th1 response, and the degree of Th1 cell terminal differentiation, were comparable in WT, IL-10R1^−/− and IL-10^−/− mice and the numbers and phenotype of Foxp3⁺ cells were largely unaltered in WSX-1^−/− mice during infection. As expected, depletion of Foxp3⁺ cells did not enhance Th1 cell polarisation or terminal differentiation during malaria infection. Our results significantly expand our understanding of how IL-27 regulates Th1 responses in vivo during inflammatory conditions and establishes WSX-1 as a critical and non-redundant regulator of the emergent Th1 effector response during malaria infection.

The cytokine interleukin 27 (IL-27), a member of the IL-12 family, is produced by cells of the innate immune system and has been shown to exert mainly suppressive effects during a wide range of inflammatory conditions, including malaria infection, where it suppresses the development of CD4⁺ T cell-dependent immunopathology. In this study we show that IL-27 suppresses the production of IFN-gamma by CD4⁺ T cells during blood stage malaria infection by preventing the development of terminally differentiated Th1 cells. We investigated the molecular mechanisms by which IL-27 inhibits the formation of terminally differentiated Th1 cells and found that it does so specifically by restricting IL-12 signals. Importantly, we demonstrate that IL-27 mediates its regulatory effects on the Th1 response through IL-10 and Foxp3⁺ regulatory T cell independent mechanisms. Thus, we have identified a new pathway though which IL-27 signalling regulates the size and quality of the Th1 response during malaria infection, which we believe will have relevance to many other pro-inflammatory conditions. Manipulation of the IL-27 pathway may therefore represent an amenable therapeutic approach during chronic inflammatory disorders.

IL-27 receptor signaling regulates CD4+ T cell chemotactic responses during infection

IL-27 exerts pleiotropic suppressive effects on naive and effector T cell populations during infection and inflammation. Surprisingly, however, the role of IL-27 in restricting or shaping effector CD4(+) T cell chemotactic responses, as a mechanism to reduce T cell-dependent tissue inflammation, is unknown. In this study, using Plasmodium berghei NK65 as a model of a systemic, proinflammatory infection, we demonstrate that IL-27R signaling represses chemotaxis of infection-derived splenic CD4(+) T cells in response to the CCR5 ligands, CCL4 and CCL5. Consistent with these observations, CCR5 was expressed on significantly higher frequencies of splenic CD4(+) T cells from malaria-infected, IL-27R-deficient (WSX-1(-/-)) mice than from infected wild-type mice. We find that IL-27 signaling suppresses splenic CD4(+) T cell CCR5-dependent chemotactic responses during infection by restricting CCR5 expression on CD4(+) T cell subtypes, including Th1 cells, and also by controlling the overall composition of the CD4(+) T cell compartment. Diminution of the Th1 response in infected WSX-1(-/-) mice in vivo by neutralization of IL-12p40 attenuated CCR5 expression by infection-derived CD4(+) T cells and also reduced splenic CD4(+) T cell chemotaxis toward CCL4 and CCL5. These data reveal a previously unappreciated role for IL-27 in modulating CD4(+) T cell chemotactic pathways during infection, which is related to its capacity to repress Th1 effector cell development. Thus, IL-27 appears to be a key cytokine that limits the CCR5-CCL4/CCL5 axis during inflammatory settings.

IL-27 enhances the survival of tumor antigen-specific CD8+ T cells and programs them into IL-10-producing, memory precursor-like effector cells

IL-27 is a member of the IL-12 family of cytokines that is comprised of an IL-12 p40-related protein subunit, EBV-induced gene 3, and a p35-related subunit, p28. IL-27 functions through IL-27R and has been shown to have potent antitumor activity via activation of a variety of cellular components, including antitumor CD8(+) T-cell responses. However, the exact mechanisms of how IL-27 enhances antitumor CD8(+) T-cell responses remain unclear. Here we show that IL-27 significantly enhances the survival of activated tumor antigen-specific CD8(+) T cells in vitro and in vivo, and programs tumor antigen-specific CD8(+) T cells into memory precursor-like effector cells, characterized by upregulation of Bcl-6, SOCS3, Sca-1, and IL-10. While STAT3 activation and the CTL survival-enhancing effects can be independent of CTL IL-10 production, we show here that IL-27-induced CTL IL-10 production contributes to memory precursor cell phenotype induction, CTL memory, and tumor rejection. Thus, IL-27 enhances antitumor CTL responses via programming tumor antigen-specific CD8(+) T cells into a unique memory precursor type of effector cells characterized by a greater survival advantage. Our results have important implications for designing immunotherapy against human cancer.

Production of interleukin-27 by human neutrophils regulates their function during bacterial infection

Septicemia is the most severe form of melioidosis caused by the Gram-negative bacterium, Burkholderia pseudomallei. Here, we show that levels of IL-27p28 transcript and protein were both significantly elevated in patients with sepsis, particularly melioidosis and in patients with unfavorable disease outcome. Moreover, human monocytes/macrophages and neutrophils were the major source of IL-27 during infection. The addition of exogenous IL-27 in vitro resulted in significantly increased bacterial survival, reduced B. pseudomallei-induced oxidative burst, and enhanced IL-1β and TNF-α production by purified neutrophils from healthy subjects. Finally, blockade of endogenous IL-27 in neutrophils using soluble IL-27 receptor antagonist prior to infection led to significantly reduced survival of bacteria and decreased IL-1β, but not TNF-α production. These results indicate a potential role for IL-27 in the suppression of anti-bacterial defense mechanisms that might contribute to disease severity in sepsis. The targeting of this cytokine may be beneficial in the management of human sepsis.

The cytokines interleukin 27 and interferon-γ promote distinct Treg cell populations required to limit infection-induced pathology

Interferon-γ (IFN-γ) promotes a population of T-bet(+) CXCR3(+) regulatory T (Treg) cells that limit T helper 1 (Th1) cell-mediated pathology. Our studies demonstrate that interleukin-27 (IL-27) also promoted expression of T-bet and CXCR3 in Treg cells. During infection with Toxoplasma gondii, a similar population emerged that limited T cell responses and was dependent on IFN-γ in the periphery but on IL-27 at mucosal sites. Transfer of Treg cells ameliorated the infection-induced pathology observed in Il27(-/-) mice, and this was dependent on their ability to produce IL-10. Microarray analysis revealed that Treg cells exposed to either IFN-γ or IL-27 have distinct transcriptional profiles. Thus, IFN-γ and IL-27 have different roles in Treg cell biology and IL-27 is a key cytokine that promotes the development of Treg cells specialized to control Th1 cell-mediated immunity at local sites of inflammation.