Therapeutic efficacy of suppressing the Jak/STAT pathway in multiple models of experimental autoimmune encephalomyelitis

Pathogenic Th cells and myeloid cells are involved in the pathogenesis of multiple sclerosis (MS) and experimental autoimmune encephalomyelitis (EAE), an animal model of MS. The JAK/STAT pathway is used by numerous cytokines for signaling and is critical for development, regulation, and termination of immune responses. Dysregulation of the JAK/STAT pathway has pathological implications in autoimmune and neuroinflammatory diseases. Many of the cytokines involved in MS/EAE, including IL-6, IL-12, IL-23, IFN-γ, and GM-CSF, use the JAK/STAT pathway to induce biological responses. Thus, targeting JAKs has implications for treating autoimmune inflammation of the brain. We have used AZD1480, a JAK1/2 inhibitor, to investigate the therapeutic potential of inhibiting the JAK/STAT pathway in models of EAE. AZD1480 treatment inhibits disease severity in myelin oligodendrocyte glycoprotein-induced classical and atypical EAE models by preventing entry of immune cells into the brain, suppressing differentiation of Th1 and Th17 cells, deactivating myeloid cells, inhibiting STAT activation in the brain, and reducing expression of proinflammatory cytokines and chemokines. Treatment of SJL/J mice with AZD1480 delays disease onset of PLP-induced relapsing-remitting disease, reduces relapses and diminishes clinical severity. AZD1480 treatment was also effective in reducing ongoing paralysis induced by adoptive transfer of either pathogenic Th1 or Th17 cells. In vivo AZD1480 treatment impairs both the priming and expansion of T cells and attenuates Ag presentation functions of myeloid cells. Inhibition of the JAK/STAT pathway has clinical efficacy in multiple preclinical models of MS, suggesting the feasibility of the JAK/STAT pathway as a target for neuroinflammatory diseases.

Altered IFN-γ-mediated immunity and transcriptional expression patterns in N-Ethyl-N-nitrosourea-induced STAT4 mutants confer susceptibility to acute typhoid-like disease

Salmonella enterica is a ubiquitous Gram-negative intracellular bacterium that continues to pose a global challenge to human health. The etiology of Salmonella pathogenesis is complex and controlled by pathogen, environmental, and host genetic factors. In fact, patients immunodeficient in genes in the IL-12, IL-23/IFN-γ pathway are predisposed to invasive nontyphoidal Salmonella infection. Using a forward genomics approach by N-ethyl-N-nitrosourea (ENU) germline mutagenesis in mice, we identified the Ity14 (Immunity to Typhimurium locus 14) pedigree exhibiting increased susceptibility following in vivo Salmonella challenge. A DNA-binding domain mutation (p.G418_E445) in Stat4 (Signal Transducer and Activator of Transcription Factor 4) was the causative mutation. STAT4 signals downstream of IL-12 to mediate transcriptional regulation of inflammatory immune responses. In mutant Ity14 mice, the increased splenic and hepatic bacterial load resulted from an intrinsic defect in innate cell function, IFN-γ-mediated immunity, and disorganized granuloma formation. We further show that NK and NKT cells play an important role in mediating control of Salmonella in Stat4(Ity14/Ity14) mice. Stat4(Ity14/Ity14) mice had increased expression of genes involved in cell-cell interactions and communication, as well as increased CD11b expression on a subset of splenic myeloid dendritic cells, resulting in compromised recruitment of inflammatory cells to the spleen during Salmonella infection. Stat4(Ity14/Ity14) presented upregulated compensatory mechanisms, although inefficient and ultimately Stat4(Ity14/Ity14) mice develop fatal bacteremia. The following study further elucidates the pathophysiological impact of STAT4 during Salmonella infection.

Opposing roles of STAT4 and Dnmt3a in Th1 gene regulation

The STAT transcription factor STAT4 is a critical regulator of Th1 differentiation and inflammatory disease. Yet, how STAT4 regulates gene expression is still unclear. In this report, we define a STAT4-dependent sequence of events including histone H3 lysine 4 methylation, Jmjd3 association with STAT4 target loci, and a Jmjd3-dependent decrease in histone H3 lysine 27 trimethylation and DNA methyltransferase (Dnmt) 3a association with STAT4 target loci. Dnmt3a has an obligate role in repressing Th1 gene expression, and in Th1 cultures deficient in both STAT4 and Dnmt3a, there is recovery in the expression of a subset of Th1 genes that is sufficient to increase IFN-γ production. Moreover, although STAT4-deficient mice are protected from the development of experimental autoimmune encephalomyelitis, mice deficient in STAT4 and conditionally deficient in Dnmt3a in T cells develop paralysis. Th1 genes that are derepressed in the absence of Dnmt3a have greater induction after the ectopic expression of the Th1-associated transcription factors T-bet and Hlx1. Together, these data demonstrate that STAT4 and Dnmt3a play opposing roles in regulating Th1 gene expression, and that one mechanism for STAT4-dependent gene programming is in establishing a derepressed genetic state susceptible to transactivation by additional fate-determining transcription factors.

Role of Th17 cells in the pathogenesis of CNS inflammatory demyelination

Multiple sclerosis (MS) is an autoimmune disease of the central nervous system (CNS). The etiology of MS is not well understood, but it is believed that myelin-specific CD4(+) T cells play a central role in initiating and orchestrating CNS inflammation. In this scenario, CD4(+) T cells, activated in the periphery, infiltrate the CNS, where, by secreting cytokines and chemokines, they start an inflammatory cascade. Given the central role of CD4(+) T cells in CNS autoimmunity, they have been studied extensively, principally by using experimental autoimmune encephalomyelitis (EAE), an animal model of MS. In the late 1980s, CD4(+) T cells, based on their cytokine production, were divided into two helper lineages, Th1 and Th2 cells. It was postulated that Th1 cells, which produce IFN-γ, mediate inflammation of the CNS in MS/EAE, while Th2 cells, which produce IL-4, have a beneficial effect in disease, because of their antagonistic effect on Th1 cells. The Th1/Th2 paradigm remained the prevailing view of MS/EAE pathogenesis until 2005, when a new lineage, Th17, was discovered. In a relatively short period of time it became apparent that Th17 cells, named after their hallmark cytokine, IL-17A, play a crucial role in many inflammatory diseases, including EAE, and likely in MS as well. The Th17 paradigm developed rapidly, initiating the debate of whether Th1 cells contribute to EAE/MS pathogenesis at all, or if they might even have a protective role due to their antagonistic effects on Th17 cells. Numerous findings support the view that Th17 cells play an essential role in autoimmune CNS inflammation, perhaps mainly in the initial phases of disease. Th1 cells likely contribute to pathogenesis, with their role possibly more pronounced later in disease. Hence, the current view on the role of Th cells in MS/EAE pathogenesis can be called the Th17/Th1 paradigm. It is certain that Th17 cells will continue to be the focus of intense investigation aimed at elucidating the pathogenesis of CNS autoimmunity.

Anti-STAT6 CTL activity in Stat6 (-/-) mice: A cautionary tale

The generation of germline gene mutations in mice has been an invaluable tool for experimental biology. However, studying immune responses that develop in the absence of a specific protein that could alter thymic selection complicates experimental interpretations. We observed that CD8⁺ T cells from Stat6^−/− mice displayed “autoreactivity” to STAT6-expressing cells, associated with specific STAT6 peptides binding to MHC class I molecules. These results suggest caution in interpreting experiments where STAT6-expressing cells are transferred into Stat6^−/− mice, or where adoptive transfer of Stat6^−/− lymphocytes is performed. Our results further highlight additional considerations when studying immune responses involving cell transfer into gene-deficient mice.

The role of IL-2 in the activation and expansion of regulatory T-cells and the development of experimental autoimmune encephalomyelitis

Multiple sclerosis (MS) is an autoimmune disease that affects ≈ 400,000 people in the US. It is a chronic, disabling disease with no cure, and the current treatment includes use of immunosuppressive drugs that often exhibit toxic side effects. Thus, there is a pressing need for alternate and more effective treatment strategies that target the components of inflammatory cells. In recent years, regulatory T-cells (Tregs) have been found to play an important role in preventing the development of autoimmunity. Thus, expansion of Tregs in vivo has the therapeutic potential against autoimmune diseases. Because Tregs constitutively express IL-2 receptors (IL-2Rs), we tested the effect of administration of IL-2 on the development of experimental autoimmune encephalomyelitis (EAE), a murine model of multiple sclerosis (MS). We used IL-2 both before (pre-treatment) or after (post-treatment) immunization with myelin oligodendrocyte glycoprotein (MOG35-55) peptide to induce EAE. The data demonstrated that pre-treatment with a moderate dose of IL-2 caused significant amelioration of EAE. Tissue histopathology of the central nervous system also confirmed the effectiveness of IL-2 pre-treatment by decreasing cellular infiltration in the spinal cord and preserving tissue integrity. IL-2 pretreatment expanded Treg cells while preventing the induction of Th17 during EAE development. In contrast, post-treatment with IL-2 failed to suppress EAE despite induction of Tregs. Together, these studies demonstrate that while expansion of Tregs using IL-2, prior to immunization or the onset of disease, can suppress the immune response, their role is limited after the antigen-specific response is triggered. Because IL-2 is used to treat certain types of cancers, and Tregs have applications in preventing the rejection of transplants, our studies also provide useful information on the use and limitations of Tregs in such clinical manifestations.

Revisiting the old link between infection and autoimmune disease with commensals and T helper 17 cells

Genetic composition and major histocompatibility complex polymorphisms unequivocally predispose to autoimmune disease, but environmental factors also play a critical role in precipitating disease in susceptible individuals. Notorious among these has been microbial infection. Older studies describing associations between microbial infection and autoimmune disease are now followed by new studies demonstrating correlations between susceptibility to autoimmune disease and commensal colonization of the intestinal tract. T helper 17 (T(H)17) cells have gained a prominent role in autoimmune disease, and notably, their development within the intestine has been linked to colonization with specific commensal bacteria. Here, we consider current views on how microbes, T(H)17 cells, and autoimmunity are connected. We speculate on how the intricate relationships among commensal, pathogen, and the host might ultimately determine susceptibility to autoimmune disease.

Live-cell imaging of the association of STAT6-GFP with mitochondria

The transcription factor STAT3 has been previously reported to be associated with mitochondria. However, we have been unable to visualize an association of STAT3-GFP, STAT3-DsRed or STAT3-Flag with mitochondria in human Hep3B hepatocytes thus far even though an association of these molecules with other cytoplasmic organelles (endosomes) was readily demonstrable. We then addressed the broader question of a possible association of other STAT-family of proteins with mitochondria by first using immunolocalization assays in Hep3B and human pulmonary arterial endothelial and smooth muscle cells. Strong anti-STAT6-immunolocalization with mitochondria was apparent in fluorescence and electron microscopy assays of cells first washed with a digitonin-sucrose buffer to remove bulk soluble STAT proteins. In live-cell imaging studies, STAT6-GFP, but not N1-GFP, was observed to constitutively colocalize with MitoTracker- and tetramethylrhodamine ethyl ester (TMRE)-positive mitochondria, and with mitochondrial F1-ATPase when assayed by immunofluorescence after fixation. This association was Tyr-phosphorylation independent in that a STAT6 truncated protein (STAT6^1-459-GFP) which lacked the SH2 domain (517–632) and the cytokine-activated Y641 phosphorylation site also accumulated in MitoTracker-positive mitochondria. This was consistent with the unexpected discovery that anti-STAT6-immunofluoresence also associated with mitochondria in mouse embryo fibroblasts (MEFs) from both wild-type and the STAT6^SH2-/SH2- mouse. MEFs from the latter mouse, which had been engineered in 1996 to be deleted in the STAT6 SH2 domain (amino acids 505–584) expressed an immune-specific ∼50 kDa protein detectable in whole cell and mitochondria-enriched fractions. Taken together, the present data provide the first definitive evidence of the association of any STAT-protein family member with mitochondria - that of STAT6.

Active induction of experimental autoimmune encephalomyelitis by MOG35-55 peptide immunization is associated with differential responses in separate compartments of the choroid plexus

BACKGROUND

There is increasing awareness that, aside from producing cerebrospinal fluid, the choroid plexus (CP) might be a key regulator of immune activity in the central nervous system (CNS) during neuroinflammation. Specifically, the CP has recently been posited to control entry of sentinel T cells into the uninflamed CNS during the early stages of neuroinflammatory diseases, like multiple sclerosis (MS) and its animal model experimental autoimmune encephalomyelitis (EAE). As the CP is compartmentalized into a stromal core containing fenestrated capillaries devoid of typical blood-brain barrier properties, surrounded by a tight junction-expressing choroidal epithelium, each of these compartments might mount unique responses that instigate the neuroinflammatory process.

METHODS

To discern responses of the respective CP stromal capillary and choroidal epithelial tissues during evolving neuroinflammation, we investigated morphology and in situ expression of 93 immune-related genes during early stages of EAE induced by immunization with myelin oligodendrocyte glycoprotein peptide (MOG35-55). Specifically, 3-D immunofluorescent imaging was employed to gauge morphological changes, and laser capture microdissection was coupled to an Immune Panel TaqMan Low Density Array to detail alterations in gene expression patterns at these separate CP sites on days 9 and 15 post-immunization (p.i.). To resolve CP effects due to autoimmunity against MOG peptide, from those due to complete Freund's adjuvant (CFA) and pertussis toxin (PTX) included in the immunization, analysis was performed on MOG-CFA/PTX-treated, CFA/PTX-treated, and naïve cohorts.

RESULTS

The CP became swollen and displayed significant molecular changes in response to MOG-CFA/PTX immunization. Both stromal capillary and choroidal epithelial tissues mounted vigorous, yet different, changes in expression of numerous genes over the time course analyzed - including those encoding adhesion molecules, cytokines, chemokines, statins, interleukins, T cell activation markers, costimulatory molecules, cyclooxygenase, pro-inflammatory transcription factors and pro-apoptotic markers. Moreover, CFA/PTX-treatment, alone, resulted in extensive, though less robust, alterations in both CP compartments.

CONCLUSIONS

MOG-CFA/PTX immunization significantly affects CP morphology and stimulates distinct expression patterns of immune-related genes in CP stromal capillary and epithelial tissues during evolving EAE. CFA/PTX treatment, alone, causes widespread gene alterations that could prime the CP to unlock the CNS to T cell infiltration during neuroinflammatory disease.

Janus-like effects of type I interferon in autoimmune diseases

In multiple sclerosis, type I interferon (IFN) is considered immune-modulatory, and recombinant forms of IFN-β are the most prescribed treatment for this disease. This is in contrast to most other autoimmune disorders, because type I IFN contributes to the pathologies. Even within the relapsing-remitting multiple sclerosis (RRMS) population, 30-50% of MS patients are non-responsive to this treatment, and it consistently worsens neuromyelitis optica, a disease similar to RRMS. In this article, we discuss the recent advances in the field of autoimmunity and introduce the theory explain how type I IFNs can be pro-inflammatory in disease that is predominantly driven by a Th17 response and are therapeutic when disease is predominantly Th1.

Association of STAT4 rs7574865 polymorphism with autoimmune diseases: a meta-analysis

The association between the signal transducer and activator of transcription 4 (STAT4) gene rs7574865 single nucleotide polymorphism and different autoimmune diseases remains controversial and ambiguous. We conducted this study to investigate whether combined evidence shows the association between STAT4 rs7574865 polymorphism and autoimmune diseases. Comprehensive Medline search and review of the references were used to get the relevant reports published before September 2011. Meta-analysis was conducted for genotype T/T (recessive effect), T/T + G/T (dominant effect) and T allele in random effects models. 40 studies with 90 comparisons including 32 systemic lupus erythematosus (SLE), 19 rheumatoid arthritis (RA), 3 type 1 diabetes (T1D), 11 Systemeric Sclerosis (SSc), 4 inflammatory bowed diseases (IBD), 3 Primary Sjogren's syndrome (pSS), 4 juvenile idiopathic arthritis (JIA), 2 Primary antiphospholipid syndrome (APS), 1 Autoimmune thyroid diseases, 1 multiple sclerosis, 1 Psoriasis, 1 Wegener's granulomatosis, 1 Type 2 diabetes, and 1 giant cell arteritis disease were available for this meta-analysis. The overall odds ratios for rs7574865 T-allele significantly increased in SLE, RA, T1D, SSc, JIA, and APS (OR = 1.56, 1.25, 1.13, 1.34, 1.25, and 2.15, respectively, P < 0.00001) and in IBD-UC and pSS (OR = 1.11 and 1.33, respectively, P < 0.05). This meta-analysis demonstrates that the STAT4 rs7574865 T allele confers susceptibility to SLE, RA, T1D, SSc, JIA, APS, IBD-UC, and pSS patients, supporting the hypothesis of association between STAT4 gene polymorphism and subgroup of autoimmune diseases.

Potential application of tregitopes as immunomodulating agents in multiple sclerosis

The induction of immunologic tolerance is an important clinical goal in autoimmunity. CD4(+) regulatory T (Treg) cells, defined by the expression of the transcription factor forkhead box P3 (FoxP3), play a central role in the control of autoimmune responses. Quantitative and qualitative defects of Tregs have been postulated to contribute to failed immune regulation in multiple sclerosis (MS) and other autoimmune diseases. This paper highlights the potential uses of T regulatory cell epitopes (Tregitopes), natural Treg epitopes found to be contained in human immunoglobulins, as immunomodulating agents in MS. Tregitopes expand Treg cells and induce "adaptive Tregs" resulting in immunosuppression and, therefore, are being considered as a potential therapy for autoimmune diseases. We will compare Tregitopes versus intravenous immunoglobulin (IVIg) in the treatment of EAE with emphasis on the potential applications of Tregitope for the treatment of MS.

Transcriptional regulation by STAT6

Signal transducer and activator of transcription (STAT) proteins are critical mediators of cytokine signaling. Among the seven STAT proteins, STAT6 is activated by IL-4 and IL-13 and plays a predominant role in the immune system. However, there is increasing evidence that STAT6 may function in other tissues and organ systems. IL-4, IL-13, and STAT6 promote humoral immunity, clearance of helminthic parasites as well as the pathogenesis of allergic disorders like asthma, food allergies, and atopic dermatitis. In this review, we will describe our current understanding of the biological functions of STAT6 and summarize recent advances in understanding the molecular mechanisms by which STAT6 regulates transcription.

T-bet in disease

The activation of immune-defense mechanisms in response to a microbial attack must be robust and appropriately tailored to fight particular types of pathogens. Infection with intracellular microorganisms elicits a type 1 inflammatory response characterized by mobilization of T helper type 1 (T(H)1) cells to the site of infection, where they are responsible for the recruitment and activation of macrophages. At the center of the type 1 inflammatory response is the transcription factor T-bet, a critical regulator of the T(H)1 differentiation program. T-bet induces the production of interferon-γ (IFN-γ) and orchestrates the T(H)1 cell-migratory program by regulating the expression of chemokines and chemokine receptors. However, tight regulation of the type 1 inflammatory response is essential for the prevention of immunopathology and the development of organ-specific autoimmunity. In this review, we discuss how T-bet expression drives autoaggressive and inflammatory processes and how its function in vivo must be delicately balanced to avoid disease.

Stat4 is critical for the balance between Th17 cells and regulatory T cells in colitis

Th17 play a central role in autoimmune inflammatory responses. Th1 are also necessary for autoimmune disease development. The interplay of Th1 signals and how they coordinate with Th17 during inflammatory disease pathogenesis are incompletely understood. In this study, by adding Stat4 deficiency to Stat6/T-bet double knockout, we further dissected the role of Stat4 in Th1 development and colitis induction. We showed that in the absence of the strong Th2 mediator Stat6, neither Stat4 nor T-bet is required for IFN-γ production and Th1 development. However, addition of Stat4 deficiency abolished colitis induced by Stat6/T-bet double-knockout cells, despite Th1 and Th17 responses. The failure of colitis induction by Stat4/Stat6/T-bet triple-knockout cells is largely due to elevated Foxp3(+) regulatory T cell (Treg) development. These results highlight the critical role of Stat4 Th1 signals in autoimmune responses in suppressing Foxp3(+) Treg responses and altering the balance between Th17 and Tregs to favor autoimmune disease.

Are Th17 cells an appropriate new target in the treatment of rheumatoid arthritis?

Th17 cells play crucial roles not only in host defense but also in many human autoimmune diseases and corresponding animal models. Although many of the fundamental principles regarding Th17 biology have been rapidly elucidated in mice, there remain numerous controversies regarding the differentiation, plasticity, and pathogenicity of human Th17 cells. In this review, we consider these open questions in comparison to what has already been clarified in mice, and discuss the potential impact of discoveries related to the Th17 pathway on the development of new therapeutic strategies in Th17 driven autoimmune diseases, specifically rheumatoid arthritis.

IL-2 suppression of IL-12p70 by a recombinant HSV-1 expressing IL-2 induces T-cell auto-reactivity and CNS demyelination

To evaluate the role of cellular infiltrates in CNS demyelination in immunocompetent mice, we have used a model of multiple sclerosis (MS) in which different strains of mice are infected with a recombinant HSV-1 expressing IL-2. Histologic examination of the mice infected with HSV-IL-2 demonstrates that natural killer cells, dendritic cells, B cells, and CD25 (IL-2rα) do not play any role in the HSV-IL-2-induced demyelination. T cell depletion, T cell knockout and T cell adoptive transfer experiments suggest that both CD8⁺ and CD4⁺ T cells contribute to HSV-IL-2-induced CNS demyelination with CD8⁺ T cells being the primary inducers. In the adoptive transfer studies, all of the transferred T cells irrespective of their CD25 status at the time of transfer were positive for expression of FoxP3 and depletion of FoxP3 blocked CNS demyelination by HSV-IL-2. The expression levels of IL-12p35 relative to IL-12p40 differed in BM-derived macrophages infected with HSV-IL-2 from those infected with wild-type HSV-1. HSV-IL-2-induced demyelination was blocked by injecting HSV-IL-2-infected mice with IL-12p70 DNA. This study demonstrates that suppression of the IL-12p70 function of macrophages by IL-2 causes T cells to become auto-aggressive. Interruption of this immunoregulatory axis results in demyelination of the optic nerve, the spinal cord and the brain by autoreactive T cells in the HSV-IL-2 mouse model of MS.

STAT6 expression in multiple cell types mediates the cooperative development of allergic airway disease

Th2 cells induce asthma through the secretion of cytokines. Two such cytokines, IL-4 and IL-13, are critical mediators of many features of this disease. They both share a common receptor subunit, IL-4Rα, and signal through the STAT6 pathway. STAT6(-/-) mice have impaired Th2 differentiation and reduced airway response to allergen. Transferred Th2 cells were not able to elicit eosinophilia in response to OVA in STAT6(-/-) mice. To clarify the role of STAT6 in allergic airway inflammation, we generated mouse bone marrow (BM) chimeras. We observed little to no eosinophilia in OVA-treated STAT6(-/-) mice even when STAT6(+/+) BM or Th2 cells were provided. However, when Th2 cells were transferred to STAT6×Rag2(-/-) mice, we observed an eosinophilic response to OVA. Nevertheless, the expression of STAT6 on either BM-derived cells or lung resident cells enhanced the severity of OVA-induced eosinophilia. Moreover, when both the BM donor and recipient lacked lymphocytes, transferred Th2 cells were sufficient to induce the level of eosinophilia comparable with that of wild-type (WT) mice. The expression of STAT6 in BM-derived cells was more critical for the enhanced eosinophilic response. Furthermore, we found a significantly higher number of CD4(+)CD25(+)Foxp3(+) T cells (regulatory T cells [Tregs]) in PBS- and OVA-treated STAT6(-/-) mouse lungs compared with that in WT animals suggesting that STAT6 limits both naturally occurring and Ag-induced Tregs. Tregs obtained from either WT or STAT6(-/-) mice were equally efficient in suppressing CD4(+) T cell proliferation in vitro. Taken together, our studies demonstrate multiple STAT6-dependent and -independent features of allergic inflammation, which may impact treatments targeting STAT6.

The role of cytokines in Guillain-Barré syndrome

Cytokines play an important role in the pathogenesis of autoimmune diseases including Guillain-Barré syndrome (GBS) and its animal model experimental autoimmune neuritis (EAN). In this article, we reviewed the current knowledge of the role of cytokines such as TNF-α, IFN-γ, IL-1β, IL-6, IL-12, IL-18, IL-23, IL-17, IL-10, IL-4 and chemokines in GBS and EAN as unraveled by studies both in the clinic and the laboratory. However, these studies occasionally yield conflicting results, highlighting the complex role that cytokines play in the disease process. Efforts to modulate cytokine function in GBS and other autoimmune disease have shown efficiency indicating that cytokines are important therapeutic targets.

Effector and regulatory T-cell subsets in autoimmunity and tissue inflammation

Many autoimmune diseases are driven by self-reactive T helper cells. Until recently, organ-specific autoimmune diseases were primarily associated with Th1 cells but not Th2 cells. However, the discovery of a number of new effector T-cell subsets, like Th17 and Th9 cells, and regulatory T cells, like Tregs and Tr1 cells, has changed the way we view and understand autoimmunity at cellular and molecular levels. In recent years, IL-17-producing Th17 cells have emerged as major players in autoimmunity. The complicated relationship between Th1 and Th17 cells, as well as the intricate balance between Tregs and Th17 cells, provides a basis for understanding the immunological mechanisms that induce and regulate autoimmunity. Here, we give an overview of the interplay between different effector T-cell subsets and regulatory T-cell subsets, and how they contribute to the development of autoimmunity and tissue inflammation.

Th1 versus Th17: are T cell cytokines relevant in multiple sclerosis?

Our understanding of the pathophysiology of multiple sclerosis (MS) has evolved significantly over the past two decades as the fields of immunology and neurobiology provide new avenues of exploration into the cause and mechanism of the disease. It has been known for decades that T cells have different cytokine phenotypes, yet the cytokine phenotype of pathogenic T cells in MS is still an area of debate. In EAE, it appears that IFNγ and IL-17, produced by Th1 and Th17 cells respectively, are not the critical factor that determines T cell encephalitogenicity. However, there are molecules such as IL-23, T-bet and STAT4, that appear to be critical, yet it is unclear whether all these molecules contribute to a common, yet undefined pathway, or act in a synergistic manner which culminates in encephalitogenicity has still to be determined. Therefore, the focus of research on effector T cells in MS should focus on pathways upstream of the cytokines that define Th1 and Th17 cells, since downstream products, such as IFNγ and IL-17, probably are not critical determinants of whether an effector T cells is capable of trafficking to the CNS and inducing inflammatory demyelination.

Heparanase upregulates Th2 cytokines, ameliorating experimental autoimmune encephalitis

Heparanase is an endo-beta-d-glucuronidase that cleaves heparan sulfate (HS) saccharide chains. The enzyme promotes cell adhesion, migration and invasion and plays a significant role in cancer metastasis, angiogenesis and inflammation. The present study focuses on the involvement of heparanase in autoimmunity, applying the murine experimental autoimmune encephalitis (EAE) model, a T-cell dependent disease often used to investigate the pathophysiology of multiple sclerosis (MS). Intraperitoneal administration of recombinant heparanase ameliorated, in a dose dependent manner, the clinical signs of the disease. In vitro and in vivo studies revealed that heparanase inhibited mitogen induced splenocyte proliferation and mixed lymphocyte reaction (MLR) through modulation of their repertoire of cytokines indicated by a marked increase in the levels of IL-4, IL-6 and IL-10, and a parallel decrease in IL-12 and TNF-alpha. Similar results were obtained with active, latent, or point mutated inactive heparanase, indicating that the observed inhibitory effect is attributed to a non-enzymatic activity of the heparanase protein. We suggest that heparanase induces upregulation of Th2 cytokines, resulting in inhibition of the inflammatory lesion of EAE.

Role of cytokines as mediators and regulators of microglial activity in inflammatory demyelination of the CNS

As the resident innate immune cells of the central nervous system (CNS), microglia fulfil a critical role in maintaining tissue homeostasis and in directing and eliciting molecular responses to CNS damage. The human disease Multiple Sclerosis and animal models of inflammatory demyelination are characterized by a complex interplay between degenerative and regenerative processes, many of which are regulated and mediated by microglia. Cellular communication between microglia and other neural and immune cells is controlled to a large extent by the activity of cytokines. Here we review the role of cytokines as mediators and regulators of microglial activity in inflammatory demyelination, highlighting their importance in potentiating cell damage, promoting neuroprotection and enhancing cellular repair in a context-dependent manner.

Th1 and Th17 cells: adversaries and collaborators

Autoreactive effector CD4+ T cells have been associated with the pathogenesis of autoimmune disorders. Early studies implicated the interferon (IFN)-gamma-producing T helper (Th)1 subset of CD4+ cells as the causal agents in the pathogenesis of autoimmunity. However, further studies have suggested a more complex story. In models thought to be driven by Th1 cells, mice lacking the hallmark Th1 cytokine IFN-gamma were not protected but tended to have enhanced susceptibility to disease. Identification of the IL-17-producing CD4+ effector cell lineage (Th17) has helped shed light on this issue. Th17 effector cells are induced in parallel to Th1, and, like Th1, polarized Th17 cells have the capacity to cause inflammation and autoimmune disease. This, together with the finding that deficiency of the Th17-related cytokine IL-23 but not the Th1-related cytokine IL-12 causes resistance, led to the notion that Th17 cells are the chief contributors to autoimmune tissue inflammation. Nevertheless, mice lacking IL-17 are not protected from disease and display elevated numbers of IFN-gamma-producing CD4+ T cells, and, in some cases, lack of IFN-gamma does confer resistance. Recent studies report overlapping as well as differential roles of these cells in tissue inflammation, which suggests the existence of a more complex relationship between these two effector T-cell subsets than has hitherto been suspected. This review will attempt to bring together current information regarding interaction, balance, and collaborative potential between the Th1 and Th17 effector lineages.

Association of signal transducer and activator of transcription 4 genetic variants with extra-intestinal manifestations in inflammatory bowel disease

AIMS

The STAT4 gene encodes a transcription factor which plays an important role in the development of inflammation of many immune-mediated diseases. We investigated the relationship between STAT4 single nucleotide polymorphisms (SNPs) and susceptibility to ulcerative colitis (UC) and Crohn's disease (CD) and disease phenotypes in the Korean population.

MAIN METHODS

We performed a case-control association study in individuals with UC (N=246), CD (N=182), and healthy controls (N=229).

KEY FINDINGS

We genotyped 8 STAT4 SNPs (rs11889341, rs7574865, rs8179673, rs6752770, rs925847, rs10168266, rs10181656, and rs11685878) in the STAT4 gene in patients and controls. SNP rs925847 in the STAT4 gene was significantly associated with susceptibility to UC (P=0.025; OR=0.63) in dominant genotype analysis, though none of these SNPs were associated with CD susceptibility. Moreover, a significant association was identified between SNP rs11889341 and joint involvement (P=0.040; OR=3.79), and between SNP rs925847 and eye involvement (P=0.030; OR=2.42) in UC patients. For CD, rs925847 genetic variant was associated with joint (P=0.029; OR=3.93) and perianal lesions (P=0.033; OR=2.27).

SIGNIFICANCE

Our data demonstrated that the STAT4 genetic variants could predispose an individual to IBD and its extra-intestinal ailments in Koreans, suggesting the common pathogenesis of IBD (especially, extra-intestinal manifestations) and other autoimmune diseases.

A meta-analysis of the association of STAT4 polymorphism with systemic lupus erythematosus

STAT4 has been newly identified as a susceptibility gene for systemic lupus erythematosus (SLE) in recent reports. To more precisely estimate the association between STAT4 polymorphism and SLE risk, a meta-analysis was performed. Studies on the association of STAT4 rs7574865 or rs7601754 with SLE were fully considered and carefully selected using three electronic databases (PubMed, Embase, and Web of Science). A total of 17 comparisons from 8 relevant studies involving 7,381 patients and 11,431 controls were included to analyze the association between STAT4 rs7574865 and SLE risk. The pooled OR for the minor T allele of STAT4 rs7574865 was 1.65 (95% CI 1.56-1.75, P < 0.001) in SLE. In a subgroup analysis by ethnicity, the degree of risk of STAT4 rs7574865 with SLE susceptibility was similar in populations of European or Asian origin, although significant differences in the minor T allele frequencies were observed in the two population controls. As for rs7601754, there were five comparisons from four relevant studies involving 2,498 patients and 4,825 controls in this meta-analysis. The pooled OR for the minor C allele of STAT4 rs7601754 was 0.67 (95% CI 0.59-0.75, P < 0.001) in SLE. Conversely, the major T allele of STAT4 rs7601754 might be a risk factor for SLE risk. In conclusion, our results do support STAT4 rs7574865 polymorphism as a susceptibility factor for SLE in populations of European and Asian origin. Our results also suggest that STAT4 rs7601754 polymorphism might be associated with SLE risk.

Autoimmunity: increasing suspects in the CD4+ T cell lineup

Chronic reactivity of CD4(+) T cells to autoantigens and to components of the commensal flora drive destructive inflammation in a variety of mouse models of autoimmunity. Insight gained using these models is empowering translational research into human disease. Immunologists are trying to assign disease culpability to one of the ever-growing number of T helper (T(H)) cell subsets. Although recent discovery of the interleukin 17-producing T(H)-17 lineage appeared to supplant the pre-eminence of T(H)1 cells in promoting autoimmunity, the newest data defy simple paradigms. Here we speculate on the respective contributions to autoimmunity made by an increasingly complex list of T(H) subsets and argue that the T(H)1 phenotype may be staging a comeback.

Carcinoembryonic antigen-related cell adhesion molecule 1 modulates experimental autoimmune encephalomyelitis via an iNKT cell-dependent mechanism

Carcinoembryonic antigen-related cellular adhesion molecule 1 (CEACAM1) is a CEA family member that has been reported to have an important role in the regulation of Th1-mediated colitis. In this study, we examined the role of CEACAM1 in an animal model of multiple sclerosis, experimental autoimmune encephalomyelitis (EAE). Treatment of C57BL/6J mice with CEACAM1-Fc fusion protein, a homophilic ligand of CEACAM1, inhibited the severity of EAE and reduced myelin oligodendrocyte glycoprotein-derived peptide (MOG(35-55))-reactive interferon-gamma and interleukin-17 production. In contrast, treatment of these animals with AgB10, an anti-mouse CEACAM1 blocking monoclonal antibody, generated increased severity of EAE in association with increased MOG(35-55)-specific induction of both interferon-gamma and interleukin-17. These results indicated that the signal elicited through CEACAM1 ameliorated EAE disease severity. Furthermore, we found that there was both a rapid and enhanced expression of CEACAM1 on invariant natural killer T cells after activation. The effect of CEACAM1-Fc fusion protein and anti-CEACAM1 mAb on both EAE and MOG(35-55)-reactive cytokine responses were abolished in invariant natural killer T cell-deficient Jalpha18(-/-) mice. Taken together, the ligation of CEACAM1 negatively regulates the severity of EAE by reducing MOG(35-55)-specific induction of both interferon-gamma and interleukin-17 via invariant natural killer T cell-dependent mechanisms.

Blocking angiotensin-converting enzyme induces potent regulatory T cells and modulates TH1- and TH17-mediated autoimmunity

The renin-angiotensin-aldosterone system (RAAS) is a major regulator of blood pressure. The octapeptide angiotensin II (AII) is proteolytically processed from the decapeptide AI by angiotensin-converting enzyme (ACE), and then acts via angiotensin type 1 and type 2 receptors (AT1R and AT2R). Inhibitors of ACE and antagonists of the AT1R are used in the treatment of hypertension, myocardial infarction, and stroke. We now show that the RAAS also plays a major role in autoimmunity, exemplified by multiple sclerosis (MS) and its animal model, experimental autoimmune encephalomyelitis (EAE). Using proteomics, we observed that RAAS is up-regulated in brain lesions of MS. AT1R was induced in myelin-specific CD4+ T cells and monocytes during autoimmune neuroinflammation. Blocking AII production with ACE inhibitors or inhibiting AII signaling with AT1R blockers suppressed autoreactive TH1 and TH17 cells and promoted antigen-specific CD4+FoxP3+ regulatory T cells (Treg cells) with inhibition of the canonical NF-kappaB1 transcription factor complex and activation of the alternative NF-kappaB2 pathway. Treatment with ACE inhibitors induces abundant CD4+FoxP3+ T cells with sufficient potency to reverse paralytic EAE. Modulation of the RAAS with inexpensive, safe pharmaceuticals used by millions worldwide is an attractive therapeutic strategy for application to human autoimmune diseases.

IL-9 induces differentiation of TH17 cells and enhances function of FoxP3+ natural regulatory T cells

The development of T helper (T(H))17 and regulatory T (T(reg)) cells is reciprocally regulated by cytokines. Transforming growth factor (TGF)-beta alone induces FoxP3(+) T(reg) cells, but together with IL-6 or IL-21 induces T(H)17 cells. Here we demonstrate that IL-9 is a key molecule that affects differentiation of T(H)17 cells and T(reg) function. IL-9 predominantly produced by T(H)17 cells, synergizes with TGF-beta1 to differentiate naïve CD4(+) T cells into T(H)17 cells, while IL-9 secretion by T(H)17 cells is regulated by IL-23. Interestingly, IL-9 enhances the suppressive functions of FoxP3(+) CD4(+) T(reg) cells in vitro, and absence of IL-9 signaling weakens the suppressive activity of nT(regs) in vivo, leading to an increase in effector cells and worsening of experimental autoimmune encephalomyelitis. The mechanism of IL-9 effects on T(H)17 and T(regs) is through activation of STAT3 and STAT5 signaling. Our findings highlight a role of IL-9 as a regulator of pathogenic versus protective mechanisms of immune responses.

CD4+ T-cell-mediated anti-tumor immunity can be uncoupled from autoimmunity via the STAT4/STAT6 signaling axis

Previous reports have suggested that autoimmune sequelae may be an unavoidable consequence of successful immunization against tumor-associated antigens, which are typically non-mutated self-antigens. Using a melanoma model, we demonstrated that CD4(+) T-cell-mediated anti-tumor immunity and autoimmunity could be separated by modulating the STAT4/STAT6 signaling axis. Our results have revealed an unexpected dichotomy in the effector phase following cancer vaccination where anti-tumor immunity is mediated via a STAT6 and IL-4-dependent pathway, whereas autoimmune pathology is mediated via STAT4 through a mechanism that relies partially on IFN-gamma. Our results offer a possibility to elicit specific anti-tumor responses without triggering unwanted tissue autoimmune diseases.

Systems-based medicine approaches to understand and treat complex diseases. The example of multiple sclerosis

Systems medicine is an emerging concept that acknowledges the complexity of a multitude of non-linear interactions among molecular and physiological variables. Under this new paradigm, rather than a collection of symptoms, diseases are seen as the product of deviations from a robust steady state compatible with life. This concept requires the incorporation of mathematics and physics to the more classical arsenal of physiology and molecular biology with which physicians are trained today. This review explores the diverse types of information that can be accumulated towards the understanding of multiple sclerosis (MS), a complex autoimmune disease that targets the central nervous system (CNS). The challenge of data integration and modeling of dynamical systems is discussed in the context of disease susceptibility and response to treatment. A theoretical framework that supports the use of combination therapy is also presented.

Association studies of the SAS-ZFAT, IL-23R, IFIH1 and FOXP3 genes in autoimmune thyroid disease

Autoimmune thyroid diseases (AITDs) are complex diseases caused by an interaction between susceptibility genes and environmental triggers. Genetic susceptibility in combination with external factors, such as dietary iodine, is believed to initiate the autoimmune response against thyroid antigens. Abundant epidemiological data, including family and twin studies, point to a strong genetic influence in the development of AITDs. Various techniques have been employed to identify genes contributing to the etiology of AITDs, including candidate gene analysis and whole-genome screening. These studies have enabled the identification of several loci (genetic regions) that are linked to AITDs and, in some of these loci, putative AITD-susceptibility genes have been identified. Some of these genes/loci are unique to Graves' disease (GD) and Hashimoto's thyroiditis (HT), and some are common to both diseases, indicating that there is a shared genetic susceptibility to GD and HT. The putative GD and HT susceptibility genes include both immune-modifying genes (e.g., HLA, CTLA-4 and PTPN22) and thyroid-specific genes (e.g., TSHR and Tg). In this special report, we focus on the newest genes identified and not on those previously identified, such as HLA and CTLA-4, for which there are many reviews.

Molecular changes in white matter adjacent to an active demyelinating lesion in early multiple sclerosis

A stereotactic biopsy of a 17-year-old woman revealed an active inflammatory demyelinating lesion compatible with pattern III multiple sclerosis (MS) according to Lucchinetti et al. The biopsy included a white matter region distant from the active inflammatory demyelinating lesion with abnormal MRI signal, lacking histopathological signs of demyelination and/or oligodendrocyte apoptosis. Expression analysis of this area revealed a strong up-regulation of neuronal nitric oxide synthase (nNOS). Furthermore, detection of nitrotyrosine provided evidence for reactive nitrogen species (RNS)-mediated damage to oligodendrocytes. Concomitantly, genes involved in neuroprotection against oxidative stress such as heme oxygenase 1 were up-regulated. Even though a single case report, this study shows earliest molecular changes in white matter surrounding an actively demyelinating lesion during the first manifestation of MS, pointing toward a more widespread pathological process. Therapeutic targeting of the identified mechanisms of tissue injury might be crucial to prevent further lesion formation or secondary tissue damage.

Targeted depletion of lymphotoxin-alpha-expressing TH1 and TH17 cells inhibits autoimmune disease

Uncontrolled T helper type 1 (T(H)1) and T(H)17 cells are associated with autoimmune responses. We identify surface lymphotoxin-alpha (LT-alpha) as common to T(H)0, T(H)1 and T(H)17 cells and employ a unique strategy to target these subsets using a depleting monoclonal antibody (mAb) directed to surface LT-alpha. Depleting LT-alpha-specific mAb inhibited T cell-mediated models of delayed-type hypersensitivity and experimental autoimmune encephalomyelitis. In collagen-induced arthritis (CIA), preventive and therapeutic administration of LT-alpha-specific mAb inhibited disease, and immunoablated T cells expressing interleukin-17 (IL-17), interferon-gamma and tumor necrosis factor-alpha (TNF-alpha), whereas decoy lymphotoxin-beta receptor (LT-betaR) fusion protein had no effect. A mutation in the Fc tail, rendering the antibody incapable of Fcgamma receptor binding and antibody-dependent cellular cytotoxicity activity, abolished all in vivo effects. Efficacy in CIA was preceded by a loss of rheumatoid-associated cytokines IL-6, IL-1beta and TNF-alpha within joints. These data indicate that depleting LT-alpha-expressing lymphocytes with LT-alpha-specific mAb may be beneficial in the treatment of autoimmune disease.

High-density genotyping of STAT4 reveals multiple haplotypic associations with systemic lupus erythematosus in different racial groups

OBJECTIVE

Systemic lupus erythematosus (SLE) is the prototypical systemic autoimmune disorder, with complex etiology and a strong genetic component. Recently, gene products involved in the interferon pathway have been under intense investigation in terms of the pathogenesis of SLE. STAT-1 and STAT-4 are transcription factors that play key roles in the interferon and Th1 signaling pathways, making them attractive candidates for involvement in SLE susceptibility.

METHODS

Fifty-six single-nucleotide polymorphisms (SNPs) across STAT1 and STAT4 on chromosome 2 were genotyped using the Illumina platform, as part of an extensive association study in a large collection of 9,923 lupus patients and control subjects from different racial groups. DNA samples were obtained from the peripheral blood of patients with SLE and control subjects. Principal components analyses and population-based case-control association analyses were performed, and the P values, false discovery rate q values, and odds ratios with 95% confidence intervals were calculated.

RESULTS

We observed strong genetic associations with SLE and multiple SNPs located within STAT4 in different ethnic groups (Fisher's combined P = 7.02 x 10(-25)). In addition to strongly confirming the previously reported association in the third intronic region of this gene, we identified additional haplotypic association across STAT4 and, in particular, a common risk haplotype that is found in multiple racial groups. In contrast, only a relatively weak suggestive association was observed with STAT1, probably due to its proximity to STAT4.

CONCLUSION

Our findings indicate that STAT4 is likely to be a crucial component in SLE pathogenesis in multiple racial groups. Knowledge of the functional effects of this association, when they are revealed, might improve our understanding of the disease and provide new therapeutic targets.

T-bet is essential for encephalitogenicity of both Th1 and Th17 cells

The extent to which myelin-specific Th1 and Th17 cells contribute to the pathogenesis of experimental autoimmune encephalomyelitis (EAE) is controversial. Combinations of interleukin (IL)-1β, IL-6, and IL-23 with transforming growth factor β were used to differentiate myelin-specific T cell receptor transgenic T cells into Th17 cells, none of which could induce EAE, whereas Th1 cells consistently transferred disease. However, IL-6 was found to promote the differentiation of encephalitogenic Th17 cells. Further analysis of myelin-specific T cells that were encephalitogenic in spontaneous EAE and actively induced EAE demonstrated that T-bet expression was critical for pathogenicity, regardless of cytokine expression by the encephalitogenic T cells. These data suggest that encephalitogenicity of myelin-specific T cells appears to be mediated by a pathway dependent on T-bet and not necessarily pathway-specific end products, such as interferon γ and IL-17.

Protection from EAE by IL-4Ralpha(-/-) macrophages depends upon T regulatory cell involvement

The administration of Th2 cytokines or immune deviation to a Th2 phenotypic response has been shown to protect against the autoimmune pathology of experimental autoimmune encephalomyelitis (EAE). To better understand the function of Th2 cytokines in the induction stage of EAE in the absence of an overt Th2 response, we immunized IL-4 receptor alpha-deficient (IL-4Ralpha(-/-)) mice, which are unable to respond to either IL-4 or IL-13. Contrary to expectations, mice lacking IL-4Ralpha had a lower incidence of EAE and a delayed onset compared to WT BALB/c mice; however, this delay did not correlate to an alteration in the Th1/Th17 cytokine balance. Instead, IL-4Ralpha-responsive macrophages were essential promoters of disease as macrophage-specific IL-4Ralpha-deficient (LysM(cre)IL-4Ralpha(-/lox)) mice were protected from EAE. The protection afforded by IL-4Ralpha-deficiency was not due to IL-10-, IFN-gamma-, NO- or IDO-mediated suppression of T-cell responses but was dependent upon the presence of regulatory T cells (Tregs). This investigation highlights the importance of macrophages and Tregs in regulating central nervous system inflammation and demonstrates that macrophages activated in the absence of Th2 cytokines can promote disease suppression by Tregs.

MOG(35-55) i.v suppresses experimental autoimmune encephalomyelitis partially through modulation of Th17 and JAK/STAT pathways

Intravenous (i.v.) administration of encephalitogenic peptide can effectively prevent experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis; however, the underlying cellular and molecular mechanisms are not fully understood. In this study, we induced i.v. tolerance to EAE by administration of MOG(35-55) peptide and determined the effect of this approach on intracellular signaling pathways of the IL-23/IL-17 system, which is essential for the pathogenesis of MS/EAE. In tolerized mice, phosphorylation of JAK/STAT-1, -4, ERK1/2 and NF-kappaBp65 were significantly reduced in splenocytes and the central nervous system. MOG i.v. treatment led to significantly lower production of IL-17, and administration of exogenous IL-17 slightly broke immune tolerance, which was associated with reduced activation of STAT4 and NF-kappaB. Suppressed phosphorylation of these pathway molecules was primarily evident in CD11b(+) and small numbers of CD4(+), CD8(+) and CD11c(+) cells. More importantly, adoptive transfer of CD11b(+) splenocytes of tolerized mice effectively delayed onset and reduced clinical severity of actively induced EAE. This study correlates MOG i.v. tolerance with modulation of Jak/STAT signaling pathways and investigates novel therapeutic avenues for the treatment of EAE/MS.

Oral tolerization with cardiac myosin peptide (614-629) ameliorates experimental autoimmune myocarditis: role of STAT 6 genes in BALB/CJ mice

INTRODUCTION

Experimental autoimmune myocarditis (EAM) is mediated by myocardial infiltration by myosin-specific T cells secreting inflammatory cytokines.

MATERIALS AND METHODS

To clarify the role of cytokines in EAM, we compared STAT 6-deficient ((-/-)) with STAT 4(-/-) and wild-type (BALB/CJ) mice following immunization with cardiac myosin peptide (614-629).

RESULTS

Wild-type mice developed severe disease with a small increase in severity in STAT 6(-/-) mice, while STAT 4(-/-) mice were resistant to EAM. STAT 6(-/-) mice had increased splenocyte proliferation and INF-gamma production versus wild type, while STAT 4(-/-) mice had decreased proliferation and INF-gamma. Following oral administration of myosin (614-629), tolerization was induced in wild-type mice evidenced by amelioration of myocarditis and up-regulation of IL-4. Adoptive transfer of splenocytes from orally tolerized mice resulted in inhibition of disease in STAT 6(-/-) mice.

CONCLUSION

These results demonstrate that oral tolerization ameliorates EAM in BALB/CJ mice and indicate a down-regulatory role for STAT 6 genes.

Association studies of the IL-23R gene in autoimmune thyroid disease in the Japanese population

Autoimmune thyroid diseases (AITDs), including Graves' disease (GD) and Hashimoto's thyroiditis (HT), are caused by interplays of genetic factors and environmental triggers. Interleukin-23 and its receptor (IL-23R) guide T cells towards the Th17 phenotype. IL-23R single nucleotide polymorphisms (SNPs) have been shown to be associated with several autoimmune diseases, including Crohn's disease and rheumatoid arthritis, and Graves' ophthalmopathy (GO) in Caucasians. To determine whether variants in the IL-23R gene are associated with AITDs in Japanese, 464 Japanese AITD patients (290 with GD, 174 with HT) and 179 matched Japanese control subjects were genotyped for four SNPs spanning the IL-23R gene. SNPs rs11209026 and rs7530511 were genotyped using TaqMan allelic discrimination assays and SNPs rs2201841 and rs10889677 were genotyped using a fluorescent-based restriction fragment length polymorphism method. Case-control association studies were performed using the chi(2) and Fisher's exact tests with Yates correction. Of the four SNPs rs11209026 was non-polymorphic in our dataset. The other three SNPs were not associated with GD or GO or HT in our Japanese population. These results suggest that the IL-23R gene is associated with AITDs only in a specific ethnic group.

Late developmental plasticity in the T helper 17 lineage

Development of T helper (Th) 17 cells requires transforming growth factor (TGF)-beta and interleukin (IL)-6 and is independent of the Th1 pathway. Although T cells that produce interferon (IFN)-gamma are a recognized feature of Th17 cell responses, mice deficient for STAT4 and T-bet-two prototypical Th1 transcription factors-are protected from autoimmunity associated with Th17 pathogenesis. To examine the fate and pathogenic potential of Th17 cells and origin of IFN-gamma-producing T cells that emerge during Th17 immunity, we developed IL-17F reporter mice that identify cells committed to expression of IL-17F and IL-17A. Th17 cells required TGF-beta for sustained expression of IL-17F and IL-17A. In the absence of TGF-beta, both IL-23 and IL-12 acted to suppress IL-17 and enhance IFN-gamma production in a STAT4- and T-bet-dependent manner, albeit with distinct efficiencies. These results support a model of late Th17 developmental plasticity with implications for autoimmunity and host defense.

T-bet and eomesodermin play critical roles in directing T cell differentiation to Th1 versus Th17

Th1 and Th17 cells are crucial in immune regulation and autoimmune disease development. By adding Stat6 deficiency to T-bet deficiency, and thus negating effects from elevated levels of IL-4/Stat6/GATA3 Th2 signals in T-bet-deficient cells, we investigated the signals important for Th1 and Th17 cell differentiation and their role in colitis development. The data reveal that Eomesodermin compensates T-bet deficiency for IFN-gamma and Th1 development. However, without T-bet, IFN-gamma production and Th1 differentiation are susceptible to inhibition by IL-6 and TGFbeta. As a result, Th17 development is strongly favored, the threshold for TGFbeta requirement is lowered, and IL-6 drives Th17 differentiation, elucidating a critical role for T-bet in directing T cell differentiation to Th1 vs Th17. In contrast to IL-6 plus TGFbeta-driven Th17, IL-6-driven Th17 cells do not express IL-10 and they induce a more intense colitis. Naive CD4 T cells deficient in Stat6 and T-bet also induce a Th17-dominant colitis development in vivo. Our data provide new insights into the choice between Th1 and Th17 development and their roles in autoimmunity.

A tale of two STAT6 knock out mice in the induction of experimental autoimmune encephalomyelitis

T helper 2 (Th2) cytokines are known to be important in protection against experimental autoimmune encephalomyelitis (EAE). To investigate the role of the signal transducer and activator of transcription factor 6 (STAT6) in EAE we used mice with two different targeted disruptions of the STAT6 gene. In this report, we show that mice with a targeted deletion of the first coding exon of the SH2 domain of STAT6 induce Th2 cell differentiation and are resistant to EAE induction. By contrast, STAT6(-/-) mice generated by deletion of amino acids 505 to 584 encoding the SH2 domain of STAT6 are defective in Th2 cell differentiation and develop very severe EAE. These results suggest that an altered STAT6 gene can be more efficient than wild type STAT6 in regulating the autoimmune response in EAE.

Stat4 isoforms differentially regulate inflammation and demyelination in experimental allergic encephalomyelitis

Experimental allergic encephalomyelitis (EAE) is a T cell-mediated autoimmune disease model of multiple sclerosis. Signal transducer and activator of transcription 4 (Stat4) is a transcription factor activated by IL-12 and IL-23, two cytokines known to play important roles in the pathogenesis of EAE by inducing T cells to secrete IFN-gamma and IL-17, respectively. We and others have previously shown that therapeutic intervention or targeted disruption of Stat4 was effective in ameliorating EAE. Recently, a splice variant of Stat4 termed Stat4beta has been characterized that lacks 44 amino acids at the C terminus of the full-length Stat4alpha. In this study we examined whether T cells expressing either isoform could affect the pathogenesis of EAE. We found that transgenic mice expressing Stat4beta on a Stat4-deficient background develop an exacerbated EAE compared with wild-type mice following immunization with myelin oligodendrocyte glycoprotein peptide 35-55, while Stat4alpha transgenic mice have greatly attenuated disease. The differential development of EAE in transgenic mice correlates with increased IFN-gamma and IL-17 in Stat4beta-expressing cells in situ, contrasting increased IL-10 production by Stat4alpha-expressing cells. This study demonstrates that Stat4 isoforms differentially regulate inflammatory cytokines in association with distinct effects on the onset and severity of EAE.

A rush to judgment on Th17

Some immunologists have characterized T helper (Th)17 T cells as the master mediators of tissue damage in a variety of pathological conditions. New data now demonstrate that Th1 and Th17 T cells are independently capable of inducing disease in two established models of autoimmunity. Thus, the role of Th17 cytokines as the central mediators of pathological tissue damage seems to require clarification.

Stat6 signaling suppresses VLA-4 expression by CD8+ T cells and limits their ability to infiltrate tumor lesions in vivo

VLA-4 plays a critical role in T cell trafficking into inflammatory sites. Our recent studies have suggested that VLA-4 expression on CD8+ T cells is negatively controlled by IL-4 and serves as a functionally distinguishing variable for why Type-1, but not Type-2, CD8+ T cells are able to traffic into tumors. In this study, using in vitro culture of murine CD8+ T cells under Type-1 and Type-2 cytokine conditions, we show that IL-4-mediated down-regulation of VLA-4 expression is completely abrogated in Stat6-deficient CD8+ T cells. Conversely, CD8+ T cells expressing a constitutively active mutant form Stat6 (Stat6VT) failed to express VLA-4 even in the absence of IL-4-stimulation. Notably, Type-2 CD8+ T cells developed from Stat6-/- but not wild-type mice were competent to migrate into tumor lesions in vivo. These results suggest that Stat6-signaling is necessary and sufficient to restrict CD8+ T cell expression of VLA-4 (by IL-4), thereby serving as a regulator for CD8+ T cell infiltration into tumors.

Distinct functions of autoreactive memory and effector CD4+ T cells in experimental autoimmune encephalomyelitis

The persistence of human autoimmune diseases is thought to be mediated predominantly by memory T cells. We investigated the phenotype and migration of memory versus effector T cells in vivo in experimental autoimmune encephalomyelitis (EAE). We found that memory CD4(+) T cells up-regulated the activation marker CD44 as well as CXCR3 and ICOS, proliferated more and produced more interferon-gamma and less interleukin-17 compared to effector T cells. Moreover, adoptive transfer of memory T cells into T cell receptor (TCR)alphabeta(-/-) recipients induced more severe disease than did effector CD4(+) T cells with marked central nervous system inflammation and axonal damage. The uniqueness of disease mediated by memory T cells was confirmed by the differential susceptibility to immunomodulatory therapies in vivo. CD28-B7 T cell costimulatory signal blockade by CTLA4Ig suppressed effector cell-mediated EAE but had minimal effects on disease induced by memory cells. In contrast, ICOS-B7h blockade exacerbated effector T cell-induced EAE but protected from disease induced by memory T cells. However, blockade of the OX40 (CD134) costimulatory pathway ameliorated disease mediated by both memory and effector T cells. Our data extend the understanding of the pathogenicity of autoreactive memory T cells and have important implications for the development of novel therapies for human autoimmune diseases.