Interleukin-12 receptor/STAT4 signaling is required for the development of autoimmune myocarditis in mice by an interferon-gamma-independent pathway

The Role of the Immune System in Pathobiology and Therapy of Myocarditis: A Review

The role of the immune system in myocarditis onset and progression involves a range of complex cellular and molecular pathways. Both innate and adaptive immunity contribute to myocarditis pathogenesis, regardless of its infectious or non-infectious nature and across different histological and clinical subtypes. The heterogeneity of myocarditis etiologies and molecular effectors is one of the determinants of its clinical variability, manifesting as a spectrum of disease phenotype and progression. This spectrum ranges from a fulminant presentation with spontaneous recovery to a slowly progressing, refractory heart failure with ventricular dysfunction, to arrhythmic storm and sudden cardiac death. In this review, we first examine the updated definition and classification of myocarditis at clinical, biomolecular and histopathological levels. We then discuss recent insights on the role of specific immune cell populations in myocarditis pathogenesis, with particular emphasis on established or potential therapeutic applications. Besides the well-known immunosuppressive agents, whose efficacy has been already demonstrated in human clinical trials, we discuss the immunomodulatory effects of other drugs commonly used in clinical practice for myocarditis management. The immunological complexity of myocarditis, while presenting a challenge to simplistic understanding, also represents an opportunity for the development of different therapeutic approaches with promising results.

Immunopathogenesis and immunomodulatory therapy for myocarditis

Myocarditis is an inflammatory cardiac disease characterized by the destruction of myocardial cells, infiltration of interstitial inflammatory cells, and fibrosis, and is becoming a major public health concern. The aetiology of myocarditis continues to broaden as new pathogens and drugs emerge. The relationship between immune checkpoint inhibitors, severe acute respiratory syndrome coronavirus 2, vaccines against coronavirus disease-2019, and myocarditis has attracted increased attention. Immunopathological processes play an important role in the different phases of myocarditis, affecting disease occurrence, development, and prognosis. Excessive immune activation can induce severe myocardial injury and lead to fulminant myocarditis, whereas chronic inflammation can lead to cardiac remodelling and inflammatory dilated cardiomyopathy. The use of immunosuppressive treatments, particularly cytotoxic agents, for myocarditis, remains controversial. While reasonable and effective immunomodulatory therapy is the general trend. This review focuses on the current understanding of the aetiology and immunopathogenesis of myocarditis and offers new perspectives on immunomodulatory therapies.

Modulation of TLR4/NFκB Pathways in Autoimmune Myocarditis

Myocarditis is an inflammatory and oxidative disorder characterized by immune cell recruitment in the damaged tissue and organ dysfunction. In this paper, we evaluated the molecular pathways involved in myocarditis using a natural compound, Coriolus versicolor, in an experimental model of autoimmune myocarditis (EAM). Animals were immunized with an emulsion of pig cardiac myosin and complete Freund's adjuvant supplemented with mycobacterium tuberculosis; thereafter, Coriolus versicolor (200 mg/Kg) was orally administered for 21 days. At the end of the experiment, blood pressure and heart rate measurements were recorded and the body and heart weights as well. From the molecular point of view, the Coriolus versicolor administration reduced the activation of the TLR4/NF-κB pathway and the levels of pro-inflammatory cytokines (INF-γ, TNF-α, IL-6, IL-17, and IL-2) and restored the levels of anti-inflammatory cytokines (IL-10). These anti-inflammatory effects were accompanied with a reduced lipid peroxidation and nitrite levels and restored the antioxidant enzyme activities (SOD and CAT) and GSH levels. Additionally, it reduced the histological injury and the immune cell recruitment (CD4+ and CD68+ cells). Moreover, we observed an antiapoptotic activity in both intrinsic (Fas/FasL/caspase-3) and extrinsic (Bax/Bcl-2) pathways. Overall, our data showed that Coriolus versicolor administration modulates the TLR4/NF-κB signaling in EAM.

COVID-19 Heart Lesions in Children: Clinical, Diagnostic and Immunological Changes

In the beginning of COVID-19, the proportion of confirmed cases in the pediatric population was relatively small and there was an opinion that children often had a mild or asymptomatic course of infection. Our understanding of the immune response, diagnosis and treatment of COVID-19 is highly oriented towards the adult population. At the same time, despite the fact that COVID-19 in children usually occurs in a mild form, there is an incomplete understanding of the course as an acute infection and its subsequent manifestations such as Long-COVID-19 or Post-COVID-19, PASC in the pediatric population, correlations with comorbidities and immunological changes. In mild COVID-19 in childhood, some authors explain the absence of population decreasing T and B lymphocytes. Regardless of the patient's condition, they can have the second phase, related to the exacerbation of inflammation in the heart tissue even if the viral infection was completely eliminated-post infectious myocarditis. Mechanism of myocardial dysfunction development in MIS-C are not fully understood. It is known that various immunocompetent cells, including both resident inflammatory cells of peripheral tissues (for example macrophages, dendritic cells, resident memory T-lymphocytes and so on) and also circulating in the peripheral blood immune cells play an important role in the immunopathogenesis of myocarditis. It is expected that hyperproduction of interferons and the enhanced cytokine response of T cells 1 and 2 types contribute to dysfunction of the myocardium. However, the role of Th1 in the pathogenesis of myocarditis remains highly controversial. At the same time, the clinical manifestations and mechanisms of damage, including the heart, both against the background and after COVID-19, in children differ from adults. Further studies are needed to evaluate whether transient or persistent cardiac complications are associated with long-term adverse cardiac events.

Cardiac myosin-specific autoimmune T cells contribute to immune-checkpoint-inhibitor-associated myocarditis

Immune checkpoint inhibitors (ICIs) are an effective therapy for various cancers; however, they can induce immune-related adverse events (irAEs) as a side effect. Myocarditis is an uncommon, but fatal, irAE caused after ICI treatments. Currently, the mechanism of ICI-associated myocarditis is unclear. Here, we show the development of myocarditis in A/J mice induced by anti-PD-1 monoclonal antibody (mAb) administration alone without tumor cell inoculation, immunization, or viral infection. Mice with myocarditis have increased cardiac infiltration, elevated cardiac troponin levels, and arrhythmia. Anti-PD-1 mAb treatment also causes irAEs in other organs. Autoimmune T cells recognizing cardiac myosin are activated and increased in mice with myocarditis. Notably, cardiac myosin-specific T cells are present in naive mice, showing a phenotype of antigen-experienced T cells. Collectively, we establish a clinically relevant mouse model for ICI-associated myocarditis and find a contribution of cardiac myosin-specific T cells to ICI-associated myocarditis development and pathogenesis.

Meeting the Challenges of Myocarditis: New Opportunities for Prevention, Detection, and Intervention—A Report from the 2021 National Heart, Lung, and Blood Institute Workshop

The National Heart, Lung, and Blood Institute (NHLBI) convened a workshop of international experts to discuss new research opportunities for the prevention, detection, and intervention of myocarditis in May 2021. These experts reviewed the current state of science and identified key gaps and opportunities in basic, diagnostic, translational, and therapeutic frontiers to guide future research in myocarditis. In addition to addressing community-acquired myocarditis, the workshop also focused on emerging causes of myocarditis including immune checkpoint inhibitors and SARS-CoV-2 related myocardial injuries and considered the use of systems biology and artificial intelligence methodologies to define workflows to identify novel mechanisms of disease and new therapeutic targets. A new priority is the investigation of the relationship between social determinants of health (SDoH), including race and economic status, and inflammatory response and outcomes in myocarditis. The result is a proposal for the reclassification of myocarditis that integrates the latest knowledge of immunological pathogenesis to refine estimates of prognosis and target pathway-specific treatments.

Association between serum inflammatory biomarkers and atrial low voltage in patients with atrial fibrillation: A phase 1 FIB-MARK study

Background

The mechanisms leading to atrial fibrosis in patients with atrial fibrillation (AF), especially in relation to inflammation, remain unclear.

Methods and Results

Forty biomarkers were measured in peripheral blood samples collected prior to catheter ablation, and the association with left atrial (LVZ) was evaluated in 16 consecutive patients. The median %LVZ was 17%. In Pearson’s correlation analysis, interleukin(IL)-17A and interferon(IFN)-γ showed the most significant positive and negative correlations with %LVZ (R = 0.35 and 0.43, P < 0.001). Furthermore, the IL-17A/IFN-γ ratio was significantly associated with %LVZ (R = 0.65, P = 0.007), as was the macrophage inflammatory protein (MIP)-1δ/IFN-γ ratio (R = 0.73, P = 0.001). The area under the receiver operator characteristics curves of the IL-17A/IFN-γ and MIP-1δ/IFN-γ ratios for detecting severe LVZ (%LVZ ≥ 10% as a reference standard) were 0.88 and 0.90, respectively. The IL-17A/IFN-γ ratio was significantly higher in patients with severe LVZ than those without (1.41 versus 0.97, P = 0.01). Furthermore, the sensitivity, specificity, and accuracy for detecting severe LVZ were 60%, 100%, and 75.0%, respectively, at a cut-off value of 1.3.

Conclusions

Among inflammatory biomarkers, the serum IL-17A/IFN-γ ratio was associated with severe left atrial LVZ in patients with AF. However, further studies are needed to clarify the role of inflammatory biomarkers in the development and progression of atrial fibrosis in patients with AF.

Dysregulated CD4+ T Cells and microRNAs in Myocarditis

Myocarditis is a polymorphic disease complicated with indeterminate etiology and pathogenesis, and represents one of the most challenging clinical problems lacking specific diagnosis and effective therapy. It is caused by a complex interplay of environmental and genetic factors, and causal links between dysregulated microribonucleic acids (miRNAs) and myocarditis have also been supported by recent epigenetic researches. Both dysregulated CD4+ T cells and miRNAs play critical roles in the pathogenesis of myocarditis, and the classic triphasic model of its pathogenesis consists of the acute infectious, subacute immune, and recovery/chronic myopathic phase. CD4+ T cells are key pathogenic factors underlying the development and progression of myocarditis, and the effector and regulatory subsets, respectively, promote and inhibit autoimmune responses. Furthermore, the reciprocal interplay of these subsets influences the pathogenesis as well. Dysregulated miRNAs along with their mRNA and protein targets have been identified in heart biopsies (intracellular miRNAs) and body fluids (circulating miRNAs) during myocarditis. These miRNAs show phase-dependent changes, and correlate with viral infection, immune status, fibrosis, destruction of cardiomyocytes, arrhythmias, cardiac functions, and outcomes. Thus, miRNAs are promising diagnostic markers and therapeutic targets in myocarditis. In this review, we review myocarditis with an emphasis on its pathogenesis, and present a summary of current knowledge of dysregulated CD4+ T cells and miRNAs in myocarditis.

Autoimmunity in Acute Myocarditis: How Immunopathogenesis Steers New Directions for Diagnosis and Treatment

PURPOSE OF REVIEW

Over the last decade, myocarditis has been increasingly recognized as common cause of sudden cardiac death in young adults and heart failure overall. The purpose of this review is to discuss hypothesis of development of non-infectious myocarditis, to provide a description of the immunopathogenesis and the most common mechanisms of autoimmunity in myocarditis, and to provide an update on therapeutic options.

RECENT FINDINGS

A new entity of myocarditis is immune checkpoint inhibitor (ICI) induced myocarditis. ICIs are used in advanced cancer to "disinhibit" the immune system and make it more aggressive in fighting cancer. This novel drug class has doubled life expectancy in metastatic melanoma and significantly increased progression free survival in advanced non-small-cell lung cancer, but comes with a risk of autoimmune diseases such as myocarditis resulting from an overly aggressive immune system. Myocarditis is an inflammatory disease of the heart with major public health impact. Thorough understanding of its immunopathogenesis is crucial for accurate diagnosis and effective treatment.

Roles and Mechanisms of Interleukin-12 Family Members in Cardiovascular Diseases: Opportunities and Challenges

Cardiovascular diseases represent a complex group of clinical syndromes caused by a variety of interacting pathological factors. They include the most extensive disease population and rank first in all-cause mortality worldwide. Accumulating evidence demonstrates that cytokines play critical roles in the presence and development of cardiovascular diseases. Interleukin-12 family members, including IL-12, IL-23, IL-27 and IL-35, are a class of cytokines that regulate a variety of biological effects; they are closely related to the progression of various cardiovascular diseases, including atherosclerosis, hypertension, aortic dissection, cardiac hypertrophy, myocardial infarction, and acute cardiac injury. This paper mainly discusses the role of IL-12 family members in cardiovascular diseases, and the molecular and cellular mechanisms potentially involved in their action in order to identify possible intervention targets for the prevention and clinical treatment of cardiovascular diseases.

Immunomodulation of autoimmune arthritis by pro-inflammatory cytokines

Pro-inflammatory cytokines promote autoimmune inflammation and tissue damage, while anti-inflammatory cytokines help resolve inflammation and facilitate tissue repair. Over the past few decades, this general feature of cytokine-mediated events has offered a broad framework to comprehend the pathogenesis of autoimmune and other immune-mediated diseases, and to successfully develop therapeutic approaches for diseases such as rheumatoid arthritis (RA). Anti-tumor necrosis factor-α (TNF-α) therapy is a testimony in support of this endeavor. However, many patients with RA fail to respond to this or other biologics, and some patients may suffer unexpected aggravation of arthritic inflammation or other autoimmune effects. These observations combined with rapid advancements in immunology in regard to newer cytokines and T cell subsets have enforced a re-evaluation of the perceived pathogenic attribute of the pro-inflammatory cytokines. Studies conducted by others and us in experimental models of arthritis involving direct administration of IFN-γ or TNF-α; in vivo neutralization of the cytokine; the use of animals deficient in the cytokine or its receptor; and the impact of the cytokine or anti-cytokine therapy on defined T cell subsets have revealed paradoxical anti-inflammatory and immunoregulatory attributes of these two cytokines. Similar studies in other models of autoimmunity as well as limited studies in arthritis patients have also unveiled the disease-protective effects of these pro-inflammatory cytokines. A major mechanism in this regard is the altered balance between the pathogenic T helper 17 (Th17) and protective T regulatory (Treg) cells in favor of the latter. However, it is essential to consider that this aspect of the pro-inflammatory cytokines is context-dependent such that the dose and timing of intervention, the experimental model of the disease under study, and the differences in individual responsiveness can influence the final outcomes. Nevertheless, the realization that pro-inflammatory cytokines can also be immunoregulatory offers a new perspective in fully understanding the pathogenesis of autoimmune diseases and in designing better therapies for controlling them.

Complete Freund's adjuvant induces experimental autoimmune myocarditis by enhancing IL-6 production during initiation of the immune response

INTRODUCTION

Complete Freund's Adjuvant (CFA) emulsified with an antigen is a widely used method to induce autoimmune disease in animal models, yet the contribution of CFA to the immune response is not well understood. We compared the effectiveness of CFA with Incomplete Freund's Adjuvant (IFA) or TiterMax Gold Adjuvant (TMax) in experimental autoimmune myocarditis (EAM) in male mice.

METHODS

EAM was induced in A/J, BALB/c, and IL6KO BALB/c male mice by injection of the myocarditogenic peptide in CFA, IFA, or TMax on days 0 and 7. EAM severity was analyzed by histology on day 21. In addition, specific flow cytometry outcomes were evaluated on day 21.

RESULTS

Only mice immunized with CFA and myocarditogenic peptide on both days 0 and 7 developed substantial myocarditis as measured by histology. We observed a significantly increased level of IL6 in the spleen 3 days after CFA immunization. In the spleen and heart on day 21, there was an expansion of myeloid cells in CFA-immunized mice, as compared to IFA or TMax-immunized animals. Recombinant IL-6 at the time of IFA immunization partially restored susceptibility of the mice to EAM. We also treated EAM-resistant IL-6 knockout mice with recombinant IL-6 around the time of the first immunization, on days -1 to 2, completely restoring disease susceptibility, showing that the requirement for IL-6 coincides with primary immunization. Examining APC populations in the lymph node draining the immunization site evidenced the contribution of IL-6 to the CFA-dependence of EAM was through controlling local dendritic cell (DC) trafficking.

CONCLUSIONS

CFA used with myocarditogenic peptide twice is required to induce EAM in both A/J and Balb/c mice. Although IFA and TiterMax induce antibody responses, only CFA preferentially induced autoantigen-specific responses. CFA expands monocytes in the heart and in the spleen. IL-6 signaling is required during short window around primary immunization to induce EAM. In addition, IL-6 deficient mice resistance to EAM could be reversed by injecting IL-6 around first immunization. IL-6 expands dendritic cell and monocytic populations and ultimately leads to a robust T-cell driven immune response in CFA immunized mice.

Transcriptome analysis reveals potential mechanisms underlying differential heart development in fast- and slow-growing broilers under heat stress

BACKGROUND

Modern fast-growing broilers are susceptible to heart failure under heat stress because their relatively small hearts cannot meet increased need of blood pumping. To improve the cardiac tolerance to heat stress in modern broilers through breeding, we need to find the important genes and pathways that contribute to imbalanced cardiac development and frequent occurrence of heat-related heart dysfunction. Two broiler lines - Ross 708 and Illinois - were included in this study as a fast-growing model and a slow-growing model respectively. Each broiler line was separated to two groups at 21 days posthatch. One group was subjected to heat stress treatment in the range of 35-37 °C for 8 h per day, and the other was kept in thermoneutral condition. Body and heart weights were measured at 42 days posthatch, and gene expression in left ventricles were compared between treatments and broiler lines through RNA-seq analysis.

RESULTS

Body weight and normalized heart weight were significantly reduced by heat stress only in Ross broilers. RNA-seq results of 44 genes were validated using Biomark assay. A total of 325 differentially expressed (DE) genes were detected between heat stress and thermoneutral in Ross 708 birds, but only 3 in Illinois broilers. Ingenuity pathway analysis (IPA) predicted dramatic changes in multiple cellular activities especially downregulation of cell cycle. Comparison between two lines showed that cell cycle activity is higher in Ross than Illinois in thermoneutral condition but is decreased under heat stress. Among the significant pathways (P < 0.01) listed for different comparisons, "Mitotic Roles of Polo-like Kinases" is always ranked first.

CONCLUSIONS

The increased susceptibility of modern broilers to cardiac dysfunction under heat stress compared to slow-growing broilers could be due to diminished heart capacity related to reduction in relative heart size. The smaller relative heart size in Ross heat stress group than in Ross thermoneutral group is suggested by the transcriptome analysis to be caused by decreased cell cycle activity and increased apoptosis. The DE genes in RNA-seq analysis and significant pathways in IPA provides potential targets for breeding of heat-tolerant broilers with optimized heart function.

Cardiac Autoimmunity: Myocarditis

Myocarditis is the inflammation of the muscle tissues of the heart (myocardium). After a pathologic cardiac-specific inflammatory process, it may progress to chronic damage and dilated cardiomyopathy. The latter is characterized by systolic dysfunction, whose clinical correlate is heart failure. Nevertheless, other acute complications may arise as consequence of tissue damage and electrophysiologic disturbances. Different etiologies are involved in triggering myocarditis. In some cases, such as giant cell myocarditis or eosinophilic necrotizing myocarditis, it is an autoimmune process. Several factors predispose the development of autoimmune myocarditis such as systemic/local primary autoimmunity, viral infection, HLA and gender bias, exposure of cryptic antigens, mimicry, and deficient thymic training/Treg induction. Once the anti-myocardium autoimmune process is triggered, several components of the immune response orchestrate a sustained attack toward myocardial tissues with particular timing and immunopathogenic features. Innate response mediated by monocytes/macrophages, neutrophils, and eosinophils parallels the adaptive response, playing a final effector role and not only a priming function. Stromal cells like fibroblast are also involved in the process through specific cytokines. Furthermore, adaptive T cell responses have anti-paradigmatic features, as Th17 response is dispensable for acute myocarditis but is the main driver of the process leading to dilated cardiomyopathy. Humoral response, thought to be a bystander, is important in the appearance of late-stage hemodynamic complications. The complexity of that process, as well as the unspecific and variable clinical presentation, had generated difficulties for diagnosis and treatment, which remain suboptimal. In this chapter, we will discuss the most relevant immunopathogenic findings from a basic science and clinical perspective.

The Quest for New Approaches in Myocarditis and Inflammatory Cardiomyopathy

Myocarditis is a diverse group of heart-specific immune processes classified by clinical and histopathological manifestations. Up to 40% of dilated cardiomyopathy is associated with inflammation or viral infection. Recent experimental studies revealed complex regulatory roles for several microribonucleic acids and T-cell and macrophage subtypes. Although the prevalence of myocarditis remained stable between 1990 and 2013 at about 22 per 100,000 people, overall mortality from cardiomyopathy and myocarditis has decreased since 2005. The diagnostic and prognostic value of cardiac magnetic resonance has increased with new, higher-sensitivity sequences. Positron emission tomography has emerged as a useful tool for diagnosis of cardiac sarcoidosis. The sensitivity of endomyocardial biopsy may be increased, especially in suspected sarcoidosis, by the use of electrogram guidance to target regions of abnormal signal. Investigational treatments on the basis of mechanistic advances are entering clinical trials. Revised management recommendations regarding athletic participation after acute myocarditis have heightened the importance of early diagnosis.

Pathogenic IL-23 signaling is required to initiate GM-CSF-driven autoimmune myocarditis in mice

Using a mouse model of experimental autoimmune myocarditis (EAM), we showed for the first time that IL-23 stimulation of CD4(+) T cells is required only briefly at the initiation of GM-CFS-dependent cardiac autoimmunity. IL-23 signal, acting as a switch, turns on pathogenicity of CD4(+) T cells, and becomes dispensable once autoreactivity is established. Il23a(-/-) mice failed to mount an efficient Th17 response to immunization, and were protected from myocarditis. However, remarkably, transient IL-23 stimulation ex vivo fully restored pathogenicity in otherwise nonpathogenic CD4(+) T cells raised from Il23a(-/-) donors. Thus, IL-23 may no longer be necessary to uphold inflammation in established autoimmune diseases. In addition, we demonstrated that IL-23-induced GM-CSF mediates the pathogenicity of CD4(+) T cells in EAM. The neutralization of GM-CSF abrogated cardiac inflammation. However, sustained IL-23 signaling is required to maintain IL-17A production in CD4(+) T cells. Despite inducing inflammation in Il23a(-/-) recipients comparable to wild-type (WT), autoreactive CD4(+) T cells downregulated IL-17A production without persistent IL-23 signaling. This divergence on the controls of GM-CSF-dependent pathogenicity on one side and IL-17A production on the other side may contribute to the discrepant efficacies of anti-IL-23 therapy in different autoimmune diseases.

Regulation of Interleukin-12 Production in Antigen-Presenting Cells

Interleukin-12 is a heterodimeric cytokine produced primarily by pathogen-activated antigen-presenting cells, particularly macrophages and dendritic cells, during encountering with intracellular microbes. IL-12 plays a key role in the activation of natural killer cells and CD4⁺ T helper cells in both innate and adaptive immune responses against infectious agents and immunosurveillance against endogenous malignancies. However, the potency of IL-12 makes it a target for stringent regulation. Indeed, the temporal, spatial, and quantitative expression of IL-12 during an immune response in a microenvironment contributes critically to the determination of the type, extent, and ultimate resolution of the reaction. Breaching of the delicate control and balance involving IL-12 frequently leads to autoimmune inflammatory disorders and pathogenesis. Thus, a better understanding of the regulatory mechanisms in the production and control of this cytokine is both scientifically significant and clinically beneficial. Here we provide an update on the research that has been conducted on this subject particularly in the last 10 years since the publication of a major thesis of this nature.

Absence of nonhematopoietic MHC class II expression protects mice from experimental autoimmune myocarditis

Experimental autoimmune myocarditis (EAM) is a CD4(+) T-cell-mediated model of human inflammatory dilated cardiomyopathies. Heart-specific CD4(+) T-cell activation is dependent on autoantigens presented by MHC class II (MHCII) molecules expressed on professional APCs. In this study, we addressed the role of inflammation-induced MHCII expression by cardiac nonhematopoietic cells on EAM development. EAM was induced in susceptible mice lacking inducible expression of MHCII molecules on all nonhematopoietic cells (pIV-/- K14 class II transactivator (CIITA) transgenic (Tg) mice) by immunization with α-myosin heavy chain peptide in CFA. Lack of inducible nonhematopoietic MHCII expression in pIV-/- K14 CIITA Tg mice conferred EAM resistance. In contrast, cardiac pathology was induced in WT and heterozygous mice, and correlated with elevated cardiac endothelial MHCII expression. Control mice with myocarditis displayed an increase in infiltrating CD4(+) T cells and in expression of IFN-γ, which is the major driver of nonhematopoietic MHCII expression. Mechanistically, IFN-γ neutralization in WT mice shortly before disease onset resulted in reduced cardiac MHCII expression and pathology. These findings reveal a previously overlooked contribution of IFN-γ to induce endothelial MHCII expression in the heart and to progress cardiac pathology during myocarditis.

Regulation of IL-10 and IL-12 production and function in macrophages and dendritic cells

Interleukin-10 and Interleukin-12 are produced primarily by pathogen-activated antigen-presenting cells, particularly macrophages and dendritic cells. IL-10 and IL-12 play very important immunoregulatory roles in host defense and immune homeostasis. Being anti- and pro-inflammatory in nature, respectively, their functions are antagonistically opposing. A comprehensive and in-depth understanding of their immunological properties and signaling mechanisms will help develop better clinical intervention strategies in therapy for a wide range of human disorders. Here, we provide an update on some emerging concepts, controversies, unanswered questions, and opinions regarding the immune signaling of IL-10 and IL-12.

STAT4 deficiency reduces the development of atherosclerosis in mice

Atherosclerosis is a chronic inflammatory process that leads to plaque formation in large and medium sized vessels. T helper 1 (Th1) cells constitute the majority of plaque infiltrating pro-atherogenic T cells and are induced via IFNγ-dependent activation of T-box (Tbet) and/or IL-12-dependent activation of signal transducer and activator of transcription 4 (STAT4). We thus aimed to define a role for STAT4 in atherosclerosis. STAT4-deficiency resulted in a ∼71% reduction (p < 0.001) in plaque burden in Stat4(-/-)Apoe(-/-) vs Apoe(-/-) mice fed chow diet and significantly attenuated atherosclerosis (∼31%, p < 0.01) in western diet fed Stat4(-/-)Apoe(-/-) mice. Surprisingly, reduced atherogenesis in Stat4(-/-)Apoe(-/-) mice was not due to attenuated IFNγ production in vivo by Th1 cells, suggesting an at least partially IFNγ-independent pro-atherogenic role of STAT4. STAT4 is expressed in T cells, but also detected in macrophages (MΦs). Stat4(-/-)Apoe(-/-)in vitro differentiated M1 or M2 MΦs had reduced cytokine production compare to Apoe(-/-) M1 and M2 MΦs that was accompanied by reduced induction of CD69, I-A(b), and CD86 in response to LPS stimulation. Stat4(-/-)Apoe(-/-) MΦs expressed attenuated levels of CCR2 and demonstrated reduced migration toward CCL2 in a transwell assay. Importantly, the percentage of aortic CD11b(+)F4/80(+)Ly6C(hi) MΦs was reduced in Stat4(-/-)Apoe(-/-) vs Apoe(-/-) mice. Thus, this study identifies for the first time a pro-atherogenic role of STAT4 that is at least partially independent of Th1 cell-derived IFNγ, and primarily involving the modulation of MΦ responses.

Therapeutic potential of STAT4 in autoimmunity

INTRODUCTION

STAT4, which acts as the major signaling transducing STATs in response to IL-12, is a central mediator in generating inflammation during protective immune responses and immune-mediated diseases.

AREAS COVERED

This review summarizes that STAT4 is essential for the differentiation and function of a wide variety of immune cells, including natural killer cells, mast cells, dendritic cells and T helper cells. In addition, STAT4-mediated signaling promoted the production of autoimmune-associated components, which are implicated in the pathogenesis of autoimmune diseases, such as rheumatoid arthritis, systemic lupus erythematosus, systemic sclerosis and psoriasis.

EXPERT OPINION

Due to its crucial roles in inflammation and autoimmunity, STAT4 may have promise as an effective therapeutic target for autoimmune diseases. Understanding the molecular mechanisms driving STAT4, together with knowledge on the ability of current immunosuppressive treatment to target this process, may open an avenue to novel therapeutic options.

Effects of microRNA-21 on the interleukin 12/signal transducer and activator of transcription 4 signaling pathway in asthmatic mice

Objective

To study the effect of microRNA-21 (miRNA-21) on the regulation of the interleukin 12 (IL-12)/signal transducer and activator of transcription 4 (STAT4) pathway in the lung tissue of asthmatic mice.

Material and methods

Forty five male C57BL/6 mice were randomly divided into three groups of 15 mice each: normal control, asthmatic model, and dexamethasone. Our mouse model of allergic asathma was established using OVA sensitization and challenge. Hematoxylin and eosin staining was performed to observe the pathological changes in lung tissue morphology. Both the total cell number and the amount of eosinophils (EOS) in the bronchoalveolar lavage fluid (BALF) were manually counted. The expression of miRNA-21 was detected by real time quantitative PCR. The expression levels of IL-12 and STAT4 in lung tissue were assayed via western blot, and immunohistochemistry was used to observe the distribution of their expression.

Results

The expression levels of miRNA-21 as well as the total number of BALF cells and EOS were significantly higher in the asthmatic model group than in the control or dexamethasone groups, with significantly higher amounts found in the dexamethasone group than in the control group. The expression levels of IL-12 and STAT4 proteins were lower in the asthmatic model group than in the control and dexamethasone groups, with a significantly lower expression of IL-12 and STAT4 in the dexamethasone group than in the control group.

Conclusions

The expression level of miRNA-21 was significantly increased and the expression level of IL-12 and STAT4 proteins was significantly decreased in allergic asthmatic mice compared with normal control mice. These findings suggest a role for miRNA-21 and the IL-12/STAT4 pathway in the development of allergic asthma.

Therapeutic administration of the chemokine CXCL1/KC abrogates autoimmune inflammatory heart disease

Myocarditis, often due to an aberrant immune response to infection, is a major cause of dilated cardiomyopathy. Microbial pattern recognition receptors, such as TLRs, orchestrate the cytokine and chemokine responses that augment or limit the severity of myocarditis. Using the mouse model of experimental autoimmune myocarditis (EAM), in which disease is induced by immunization with a heart-specific self peptide and the agonist to multiple TLRs, complete Freund's adjuvant, we found that increased serum concentrations of the chemokine CXCL1/KC correlated directly with decreased severity of myocarditis. To directly test whether CXCL1/KC caused the amelioration of myocarditis, we treated mice, after challenge with heart-specific self peptide, with exogenous recombinant CXCL1/KC. We found that the administration of recombinant mouse CXCL1/KC completely abrogated heart inflammatory infiltration and cardiomyocyte damage. Moreover, we show that TLR4 signaling is required to increase serum protein concentrations of CXCL1/KC in EAM, and we demonstrate that the administration of the TLR4 agonist LPS significantly decreased severity and prevalence of EAM and reduced the number of heart-specific self peptide reactive effector T cells. These findings reveal a novel function of CXCL1/KC in the context of organ-specific autoimmune disease that may prove useful for the treatment of inflammatory conditions that underlie human heart disease.

Galectin-9 induced myeloid suppressor cells expand regulatory T cells in an IL-10-dependent manner in CVB3-induced acute myocarditis

The objective of the study was to explore the effects of galectin-9 on myeloid suppressor cells in Coxsackievirus B3 (CVB3)-induced myocarditis and the possible mechanisms involved. For this purpose, BALB/c male mice were infected with CVB3 on day 0 and then received intraperitoneal (IP) administration of recombinant galectin-9 or phosphate-buffered saline (PBS) daily from day 3 to day 7. The phenotypes and functions of myeloid suppressor cells were evaluated. The role and mechanism of myeloid suppressor cells and subsets in CVB3-induced myocarditis in vitro were explored. We found that galectin-9 remarkably increased the frequencies of CD11b+Gr-1+ cells in the cardiac tissue and spleen with myocarditis. Ly-6G+ cells were decreased and Ly-6C+ cells were increased in galectin-9-treated mice. In addition, CD11b+Gr-1+ cells were highly effective in suppressing CD4+ T cells. Moreover, our data demonstrate that CD11b+Gr-1+ cells are capable of expanding regulatory T cells (Tregs) from a preexisting population of natural Tregs, which depends on IL-10 but not TGF-β. Our results indicate that galectin-9 therapy may represent a useful approach to ameliorate CVB3-induced myocarditis.

Fatal eosinophilic myocarditis develops in the absence of IFN-γ and IL-17A

CD4(+) T cells play a central role in inflammatory heart disease, implicating a cytokine product associated with Th cell effector function as a necessary mediator of this pathophysiology. IFN-γ-deficient mice developed severe experimental autoimmune myocarditis (EAM), in which mice are immunized with cardiac myosin peptide, whereas IL-17A-deficient mice were protected from progression to dilated cardiomyopathy. We generated IFN-γ(-/-)IL-17A(-/-) mice to assess whether IL-17 signaling was responsible for the severe EAM of IFN-γ(-/-) mice. Surprisingly, IFN-γ(-/-)IL-17A(-/-) mice developed a rapidly fatal EAM. Eosinophils constituted a third of infiltrating leukocytes, qualifying this disease as eosinophilic myocarditis. We found increased cardiac production of CCL11/eotaxin, as well as Th2 deviation, among heart-infiltrating CD4(+) cells. Ablation of eosinophil development improved survival of IFN-γ(-/-)IL-17A(-/-) mice, demonstrating the necessity of eosinophils in fatal heart failure. The severe and rapidly fatal autoimmune inflammation that developed in the combined absence of IFN-γ and IL-17A constitutes a novel model of eosinophilic heart disease in humans. This is also, to our knowledge, the first demonstration that eosinophils have the capacity to act as necessary mediators of morbidity in an autoimmune process.

Control of inflammatory heart disease by CD4+ T cells

This review focuses on autoimmune myocarditis and its sequela, inflammatory dilated cardiomyopathy (DCMI), and the inflammatory and immune mechanisms underlying the pathogenesis of these diseases. Several mouse models of myocarditis and DCMI have improved our knowledge of the pathogenesis of these diseases, informing more general problems of cardiac remodeling and heart failure. CD4(+) T cells are critical in driving the pathogenesis of myocarditis. We discuss in detail the role of T helper cell subtypes in the pathogenesis of myocarditis, the biology of T cell-derived effector cytokines, and the participation of other leukocytic effectors in mediating disease pathophysiology. We discuss interactions between these subsets in both suppressive and collaborative fashions. These findings indicate that cardiac inflammatory disease, and autoimmunity in general, may be more diverse in divergent effector mechanisms than has previously been appreciated.

The heart of the matter: protection of the myocardium from T cells

Myocardial inflammation and damage can lead to lethal acute or chronic cardiac failure. A variety of regulatory mechanisms limit the magnitude and duration of T cell responses in the heart. Insights into these regulatory mechanisms have come from studies of specific deficiencies in central or peripheral T cell tolerance which cause or enhance the severity of myocarditis. Under non-inflammatory conditions, constitutive DC presentation of cardiac peptides to naïve T cells in cardiac draining lymph nodes tolerizes recirculating naïve T cells specific for these antigens. Cardiac antigen-specific naïve T cells, especially those specific of α-myosin heavy chain peptides, become activated and differentiate into expanded clones of effector T cells under various conditions, such as cardiac infection and/or genetic variations in peripheral tolerance. The pathology that these effector cells cause in the myocardium is limited by PD-L1 expressed on myocardial cells in response to inflammatory cytokines, and by CTLA-4 dependent mechanisms. The PD-1:PD-L1 pathway works together with other control mechanisms to keep the heart safe from T cells, and combined impairment of this pathway along with other regulatory mechanisms synergize to cause myocarditis. T cell derived IFNγ contributes to the inflammatory damage to the heart in autoimmune myocarditis, but it also engages regulatory mechanisms that limit disease, including upregulation of PD-L1, and differentiation of TNF and iNOS expressing DCs from monocytes. iNOS derived from these DCs and other IFNγ stimulated cells inhibits expansion of T cells that cause myocarditis. Regulatory T cells also appear to be critical for suppression of effector T cells specific for myocardial antigens.

Immunomodulatory effects of mesenchymal stromal cells revisited in the context of inflammatory cardiomyopathy

Myocarditis is a common inflammatory cardiomyopathy, associated with cardiomyocyte apoptosis, which can lead to chronic left ventricular dysfunction. Under conventional heart failure therapy, inflammatory cardiomyopathy typically has a progressive course, indicating a need for alternative therapeutic strategies to improve long-term outcomes. Experimental and clinical studies consistently support the application of cellular transplantation as a strategy to improve myocardial function. Mesenchymal stromal cells (MSCs) mediate distinct paracrine effects supporting endogenous regeneration, but most important are their remarkable immunoregulatory properties. In this review, an overview of current knowledge on immunopathology in myocarditis will be given. Furthermore, current research regarding the immunomodulatory properties of MSCs in the context of myocarditis will be discussed. Finally, the impact of MSC priming by the environment on their functionality and the advantages of systemic administration of MSCs under myocarditis are outlined.

Expression of cathepsin K and tartrate-resistant acid phosphatase is not confined to osteoclasts but is a general feature of multinucleated giant cells: systematic analysis

OBJECTIVE

Cathepsin K and tartrate-resistant acid phosphatase (TRAP) are two proteins expressed in osteoclastic giant cells. Recently we showed that lesional multinucleated giant cells (MNGs) in pulmonary granulomatosis with polyangiitis expressed these proteins. We aimed to clarify whether the expression of these two proteins has any specificity or is a general feature of MNGs associated with multiple types of granulomatous inflammation.

METHODS

In total, 7 Crohn's disease (CD), 5 GCA, 5 giant cell myocarditis (GCM), 11 sarcoidosis and 6 tuberculosis cases were examined for expression of cathepsin K and TRAP using immunohistochemistry (IHC). Protein expression was semi-quantitatively classified as none, weak, moderate or strong. In addition, tissue TRAP activity was examined using an enzymatic reaction.

RESULTS

The expression of cathepsin K was robust in >95% of MNGs of all examined disease groups, whereas TRAP expression varied; CD, GCA and tuberculosis showed strong TRAP expression. TRAP expression in sarcoidosis and GCM was weaker (CD vs GCM, P = 0.04; CD vs sarcoidosis, P = 0.06). Compared with IHC, TRAP detection using an enzymatic colour reaction had limited sensitivity.

CONCLUSION

Expression of TRAP and cathepsin K is a general feature of MNGs and their expression might be related to histopathological pattern.

Suppressor of cytokine signaling 1 DNA administration inhibits inflammatory and pathogenic responses in autoimmune myocarditis

Myocarditis and subsequent dilated cardiomyopathy are major causes of heart failure in young adults. Myocarditis in humans is highly heterogeneous in etiology. Recent studies have indicated that a subgroup of myocarditis patients may benefit from immune-targeted therapies, because autoimmunity plays an important role in myocarditis as well as contributing to the progression to cardiomyopathy and heart failure. Suppressor of cytokine signaling (SOCS) 1 plays a key role in the negative regulation of both TLR- and cytokine receptor-mediated signaling, which is involved in innate immunity and subsequent adaptive immunity. In this study, we investigated the therapeutic effect of SOCS1 DNA administration on experimental autoimmune myocarditis (EAM) in mice. EAM was induced by s.c. immunization with cardiac-specific peptides derived from α myosin H chain in BALB/c mice. In contrast to control myocarditis mice, SOCS1 DNA-injected mice were protected from development of EAM and heart failure. SOCS1 DNA administration was effective for reducing the activation of autoreactive CD4(+) T cells by inhibition of the function of Ag-presenting dendritic cells. Our findings suggest that SOCS1 DNA administration has considerable therapeutic potential in individuals with autoimmune myocarditis and dilated cardiomyopathy.

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.

Pathogenesis and host response in Syrian hamsters following intranasal infection with Andes virus

Hantavirus pulmonary syndrome (HPS), also referred to as hantavirus cardiopulmonary syndrome (HCPS), is a rare but frequently fatal disease caused by New World hantaviruses. In humans HPS is associated with severe pulmonary edema and cardiogenic shock; however, the pathogenesis of this disease remains unclear largely due to a lack of suitable animal models for the study of disease progression. In this study we monitored clinical, virological, pathophysiological parameters and host immunological responses to decipher pathological factors and events in the lethal Syrian hamster model of HPS following intranasal inoculation of Andes virus. Transcriptional profiling of the host gene responses demonstrated a suppression of innate immune responses in most organs analyzed during the early stage of infection, except for in the lung which had low level activation of several pro-inflammatory genes. During this phase Andes virus established a systemic infection in hamsters, with viral antigen readily detectable in the endothelium of the majority of tissues analyzed by 7-8 days post-inoculation. Despite wide-spread infection, histological analysis confirmed pathological abnormalities were almost exclusively found in the lungs. Immediately preceding clinical signs of disease, intense activation of pro-inflammatory and Th1/Th2 responses were observed in the lungs as well as the heart, but not in peripheral organs, suggesting that localized immune-modulations by infection is paramount to pathogenesis. Throughout the course of infection a strong suppression of regulatory T-cell responses was noted and is hypothesized to be the basis of the aberrant immune activations. The unique and comprehensive monitoring of host immune responses to hantavirus infection increases our understanding of the immuno-pathogenesis of HPS and will facilitate the development of treatment strategies targeting deleterious host immunological responses.

Critical cytokine pathways to cardiac inflammation

Infectious disease is frequently cited as a precursor of subsequent autoimmune disease in genetically susceptible hosts. However, the precise mechanisms required for the transition from infection to autoimmunity have not been well defined. We have developed a mouse model of autoimmune myocarditis initiated by infection with Coxsackievirus B3 to trace the cytokine pathways involved. We found that greater production of interleukin-1β (IL-1β) and tumor necrosis factor-α during the early innate response to virus infection is necessary and sufficient to induce a later heart-specific autoimmune disease. Severity of the autoimmune myocarditis is determined by the profile of a number of T helper 1 (Th1) and Th2 cytokines. Th2 responses are especially pronounced in the most severe forms of myocarditis where eosinophils are prominent. The Th1 pathway can lead to infiltration of the heart, but may be dampened by concurrent INF-γ production. Th17 cytokines also contribute to disease, but the signature Th17 cytokine, IL-17A, is not required for cardiac inflammation. Rather, IL-17A is needed for progression to dilated cardiomyopathy. These findings may provide useful markers to identify individuals prone to develop an autoimmune sequel after infection and suggest future early interventions.

Autoimmune giant cell myocarditis: clinical characteristics, experimental models and future treatments

INTRODUCTION

Although prognosis in acute myocarditis is generally moderate, giant cell myocarditis shows poor prognosis. Giant cell myocarditis is considered to be an autoimmune disease, however, its pathophysiology and specific treatment is yet to be elucidated.

AREAS COVERED

This article reviews the clinical characteristics of autoimmune myocarditis and its possible future treatments. An animal model of experimental autoimmune myocarditis (EAM) is characterized by severe myocardial damage and multinucleated giant cell infiltration, and this has been used as a disease model for human acute giant cell myocarditis. Using experimental models, we reported that NF-κB, cytokines, adhesion molecules and other factors play a critical role in the development of autoimmune myocarditis.

EXPERT OPINION

Giant cell myocarditis, an autoimmune form of myocarditis, has a high mortality rate unless mechanical support or cardiac transplantation is performed. Therefore, further therapeutic applications of novel methodologies are needed to expand the number of alternative choices for treating autoimmune myocarditis.

Expression of IL-23/Th17 pathway in a murine model of Coxsackie virus B3-induced viral myocarditis

Background

The IL-23/Th17 pathway is implicated in the pathogenesis of a number of chronic inflammatory and autoimmune diseases. Whether it regulates the viral myocarditis (VMC) is unknown.

Results

To examine the pathogenesis role of IL-23/Th17 axis in VMC, we used male BALB/c mice to induced VMC by Coxsackie virus B3 (CVB3) peritoneal injection. IL-23, IL-17, and signal transducer and activator of transcription 3 (STAT3) mRNA in the myocardium of VMC mice were assessed by semi-quantitative RT-PCR. IL-23 and IL-17 protein from blood serum were evaluated by ELISA. Phosphorylated-STAT3 (p-STAT3) protein expression in the myocardium was evaluated by immunohistochemical staining. Flow cytometric analysis was used to evaluate the frequencies of Th17 subsets. Isolated CD4⁺ T cells from VMC mice were cultured with recombinant IL-23(rIL-23) in vitro. In addition, a STAT3-specific inhibitor (S3I-201) was used to test whether regulation of STAT3 could be partly responsible for Th17 diminution. Results showed that expression of IL-23, IL-17, STAT3 mRNA and protein increased in VMC mice. When purified CD4⁺ T cells derived from VMC mice were cultured in vitro with rIL-23, the frequency of Th17 cells was dramatically increased, accompanied by significantly enhanced production of IL-17 in the supernatants of cultured CD4⁺ T cells. S3I-201 significantly restrained Th17 cell proliferation.

Conclusions

The IL-23/Th17 pathway axis is strongly expressed in murine VMC, identifying a novel pathway of potential significance in viral myocarditis.

Mechanisms of IFNγ regulation of autoimmune myocarditis

A protective effect of interferon-gamma (IFNγ) has been described in a number of models of autoimmune disease, including experimental autoimmune myocarditis (EAM). Some reports have suggested that regulation of apoptosis in autoreactive lymphocytes mediate these protective functions. We examined the potential of IFNγ to regulate apoptotic mechanisms in detail, both in vitro and in vivo in EAM. We observed multiple apoptotic defects in caspase activity, and the expression of TNF superfamily members on CD4(+) T cells. In addition, we observed selective defects in CD4(+) T cell activation in response to antigenic stimulation. These activation and apoptotic defects were CD4(+) cell autonomous, independent of the genotype of APCs. Inhibition of nitric oxide production in vivo did not reproduce the severe form of EAM of IFNγ-deficient mice, indicating that this pathway does not mediate the protective effect of IFNγ. Crosswise adoptive transfer of wild type, IFNγ(-/-), and IFNγR(-/-)EAM demonstrated that IFNγ signaling was critical in CD4(+) cells, but that non-CD4(+) sources of IFNγ production were also involved in the control of disease. Together, these data indicate multiple mechanisms of autonomous and non-autonomous CD4(+) T cell regulation mediated by IFNγ in the control of autoimmune heart disease.

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.

Spontaneous autoimmune myocarditis and cardiomyopathy in HLA-DQ8.NODAbo transgenic mice

Most individuals have viral infections at some point in their life, however, only few develop autoreactivity to cardiac myosin following infection suggesting a genetic predisposition. Population studies have shown that among all the genetic factors linked with autoimmune disease development, MHC class II genes are the most significant genetic factors. Experimental autoimmune myocarditis resembling human Dilated cardiomyopathy can be induced in susceptible mice by infection with coxsackie virus as well as immunization with purified foreign and murine cardiac specific a-myosin. We generated transgenic mice lacking endogenous class II molecules, HLA-DR3.Abo and HLA-DQ8.Abo transgenic mice in NOD and HLA-DQ8.Abo in B10 background, to study the role of MHC in spontaneous autoimmunity. The HLA molecules in these mice are expressed on cell surface and can positively select CD4+ T cells expressing various Vb T cell receptors. NOD.DQ8 female mice spontaneously developed myocarditis and dilated cardiomyopathy. Histopathology of heart revealed mononuclear infiltrate consisting of CD4 and Mac-1+ cells and myocyte necrosis. NOD.DQ8 mice showed cellular and humoral autoreactive response to self cardiac myosin.. Depletion of CD8 and CD4 + cells suggested that CD8 T cells may act as regulatory cells while CD4 cells are required as effector cells. NOD.DR3 and B10.DQ8 mice did not develop any cardiac pathology suggesting DQ8 is required for predisposition to the spontaneous autoreactivity while NOD background influences onset and progression of disease. Thus these mice provide powerful tools to understand the role of HLA class II molecules in predisposition and onset of human diseases and to develop immunotherapy.

Self heat-shock protein 65-mediated regulation of autoimmune arthritis

Heat-shock proteins (Hsps) have been invoked in the pathogenesis of a variety of autoimmune diseases. The mycobacterial heat-shock protein 65 (Bhsp65) has been studied extensively as one of the antigenic triggers of autoimmunity in experimental models of, as well as patients with, rheumatoid arthritis. As Hsps are highly conserved and immunogenic, it is generally anticipated that self Hsps might serve as the endogenous targets of the immune response initiated by the homologous foreign Hsps. Contrary to this expectation, studies in the rat adjuvant arthritis (AA) model have revealed that priming of the self (rat) hsp65 (Rhsp65)-directed T cells in the Lewis rat leads to protection against AA instead of disease induction or aggravation. The arthritis-protective attribute of the self hsp65 is also evident following spontaneous priming of the anti-Rhsp65 T cells during the natural course of AA. Furthermore, immunization of rats with human hsp60, or with Bhsp65 peptides that are crossreactive with the corresponding self hsp65 peptides, leads to protection against AA. Importantly, high levels of T cell reactivity against self hsp60 in patients with juvenile idiopathic arthritis positively correlate with a favorable outcome of the disease. Thus, immune response against self hsp65 in autoimmune arthritis is protective rather than being pathogenic.

Autoimmune myocarditis: past, present and future

Heart failure has become an increasingly prevalent disorder with considerable morbidity and mortality. While many causal mechanisms such as inherited cardiomyopathies, ischemic cardiomyopathy or muscular overload are easily identified in clinical practice, the molecular mechanisms that determine the progression of heart failure or ventricular remodelling are largely unknown. Autoimmune responses and inflammation are involved in the pathogenesis of many cardiovascular diseases. There is compelling evidence that inflammatory mechanisms may contribute to progressive heart failure. Thus, myocardial infiltration of lymphocytes and mononuclear cells, increased expression of pro-inflammatory chemokines and cytokines and circulating autoantibodies are frequently observed in myocarditis and dilated cardiomyopathy. In this review we give an overview on myocarditis and describe why diagnosis and treatment of myocarditis in the clinic can be difficult. We present current animal models and describe possible experimental approaches to improve diagnosis. Finally, we give an outlook on possible drug targets by describing the latest findings in the animal models focussing on chemokines and cytokines, T cell responses and interactions, tolerance induction and the development of autoantibodies.

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.

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.

Cardiac troponins and autoimmunity: their role in the pathogenesis of myocarditis and of heart failure

Despite the widespread use of cardiac troponins as biomarkers for the diagnosis and quantitation of cardiac injury, the effect of troponin release and a possible autoimmune response to the troponins is unknown. Other investigators reported that programmed cell death-1 (PD-1)-receptor deficient mice developed severe cardiomyopathy with autoantibodies to troponin I. We found that immunization of genetically susceptible mice with troponin I but not troponin T induced a robust autoimmune response leading to marked inflammation and fibrosis in the myocardium. At later times, antibodies to cardiac myosin were detected in troponin-immunized mice. The severity of inflammation correlated with expression of chemokines RANTES, MIP-2, IP-10 and MCP-1 in the myocardium. Prior immunization with troponin I increased the severity of experimental infarctions, indicating that an autoimmune response to troponin I aggravates acute cardiac damage. Cardiac inflammation, fibrosis and functional impairment were transferred from immunized to naive recipients by CD4+ T cells, and the cytokine profile suggested both Th2 and Th17 profiles in A/J mice. Finally we identified an 18-mer of troponin I containing an immuno-dominant epitope.