AMA production in primary biliary cirrhosis is promoted by the TLR9 ligand CpG and suppressed by potassium channel blockers

Kv1.3 in the spotlight for treating immune diseases

INTRODUCTION

Kv1.3 is the main voltage-gated potassium channel of leukocytes from both the innate and adaptive immune systems. Channel function is required for common processes such as Ca2+ signaling but also for cell-specific events. In this context, alterations in Kv1.3 are associated with multiple immune disorders. Excessive channel activity correlates with numerous autoimmune diseases, while reduced currents result in increased cancer prevalence and immunodeficiencies.

AREAS COVERED

This review offers a general view of the role of Kv1.3 in every type of leukocyte. Moreover, diseases stemming from dysregulations of the channel are detailed, as well as current advances in their therapeutic research.

EXPERT OPINION

Kv1.3 arises as a potential immune target in a variety of diseases. Several lines of research focused on channel modulation have yielded positive results. However, among the great variety of specific channel blockers, only one has reached clinical trials. Future investigations should focus on developing simpler administration routes for channel inhibitors to facilitate their entrance into clinical trials. Prospective Kv1.3-based treatments will ensure powerful therapies while minimizing undesired side effects.

Breakdown in hepatic tolerance and its relation to autoimmune liver diseases

The liver is a complex immunological organ. It has both immunogenic and tolerogenic capacity. Tolerogenic potential of human liver with its protective firewalls is required to guard the body against the continuous influx of microbial product from the gut via the sinusoids and biliary tree. Immunotolerance and anergic state is maintained by a combined effort of both immune cells, parenchyma cells, epithelial and endothelial cells. Despite this, an unknown trigger can ignite the pathway towards breakdown in hepatic tolerance leading to autoimmune liver diseases. Understanding the initial stimulus which causes the hepatic immune system to switch from the regulatory arm towards self-reactive effector arm remains challenging. Dissecting this pathology using the current technological advances is crucial to develop curative immune based therapy in autoimmune liver diseases. We discuss the hepatic immune cells and non-immune cells which maintain liver tolerance and the evidence of immune system barrier breach which leads to autoimmune hepatitis, primary biliary cholangitis and primary sclerosing cholangitis.

The role of ion channels in immune-related diseases

Ion channel is an integral membrane protein that allows the permeation of charge ions across hydrophobic phospholipid membranes, including plasma membranes and organelle membranes (such as mitochondria, endoplasmic reticulum and vacuoles), which are widely distributed in various cells and tissues, such as cardiomyocytes, smooth muscle cells, and nerve cells. Ion channels establish membrane potential by regulating ion concentration and membrane potential. Membrane potential plays an important role in cells. Studies have shown that ion channels play a role in a number of immune-related diseases caused by functional defects in ion channels on immune or non-immune cells in major human organs, usually affecting specific organs or multiple organs. The present review discusses the relationship between ion channels and immune diseases in major organs of the human body.

Review on Biological Characteristics of Kv1.3 and Its Role in Liver Diseases

The liver accounts for the largest proportion of macrophages in all solid organs of the human body. Liver macrophages are mainly composed of cytolytic cells inherent in the liver and mononuclear macrophages recruited from the blood. Monocytes recruitment occurs mainly in the context of liver injury and inflammation and can be recruited into the liver and achieve a KC-like phenotype. During the immune response of the liver, macrophages/KC cells release inflammatory cytokines and infiltrate into the liver, which are considered to be the common mechanism of various liver diseases in the early stage. Meanwhile, macrophages/KC cells form an interaction network with other liver cells, which can affect the occurrence and progression of liver diseases. From the perspective of liver disease treatment, knowing the full spectrum of macrophage activation, the underlying molecular mechanisms, and their implication in either promoting liver disease progression or repairing injured liver tissue is highly relevant from a therapeutic point of view. Kv1.3 is a subtype of the voltage-dependent potassium channel, whose function is closely related to the regulation of immune cell function. At present, there are few studies on the relationship between Kv1.3 and liver diseases, and the application of its blockers as a potential treatment for liver diseases has not been reported. This manuscript reviewed the physiological characteristics of Kv1.3, the relationship between Kv1.3 and cell proliferation and apoptosis, and the role of Kv1.3 in a variety of liver diseases, so as to provide new ideas and strategies for the prevention and treatment of liver diseases. In short, by understanding the role of Kv1.3 in regulating the functions of immune cells such as macrophages, selective blockers of Kv1.3 or compounds with similar functions can be applied to alleviate the progression of liver diseases and provide new ideas for the prevention and treatment of liver diseases.

Animal Models of Autoimmune Liver Diseases: a Comprehensive Review

Autoimmune liver diseases (AILDs) are potentially life-threatening chronic liver diseases which include autoimmune hepatitis, primary biliary cholangitis, primary sclerosing cholangitis, and recently characterized IgG4-related sclerosing cholangitis. They are caused by immune attack on hepatocytes or bile ducts, with different mechanisms and clinical manifestations. The etiologies of AILDs include a susceptible genetic background, environment insults, infections, and changes of commensal microbiota, but remain complicated. Understanding of the underlying mechanisms of AILDs is mandatory for early diagnosis and intervention, which is of great importance for better prognosis. Thus, animal models are developed to mimic the pathogenesis, find biomarkers for early diagnosis, and for therapeutic attempts of AILDs. However, no animal models can fully recapitulate features of certain AILD, especially the late stages of diseases. Certain limitations include different living condition, cell composition, and time frame of disease development and resolution. Moreover, there is no IgG4 in rodents which exists in human. Nevertheless, the understanding and therapy of AILDs have been greatly advanced by the development and mechanistic investigation of animal models. This review will provide a comprehensive overview of traditional and new animal models that recapitulate different features and etiologies of distinct AILDs.

The voltage-gated potassium channel KV1.3 as a therapeutic target for venom-derived peptides

The voltage-gated potassium channel K_V1.3 is a well-established therapeutic target for a range of autoimmune diseases, in addition to being the site of action of many venom-derived peptides. Numerous studies have documented the efficacy of venom peptides that target K_V1.3, in particular from sea anemones and scorpions, in animal models of autoimmune diseases such as rheumatoid arthritis, psoriasis and multiple sclerosis. Moreover, an analogue of the sea anemone peptide ShK (known as dalazatide) has successfully completed Phase 1 clinical trials in mild-to-moderate plaque psoriasis. In this article we consider other potential therapeutic applications of inhibitors of K_V1.3, including in inflammatory bowel disease and neuroinflammatory conditions such as Alzheimer's and Parkinson's diseases, as well as fibrotic diseases. We also summarise strategies for facilitating the entry of peptides to the central nervous system, given that this will be a pre-requisite for the treatment of most neuroinflammatory diseases. Venom-derived peptides that have been reported recently to target K_V1.3 are also described. The increasing number of autoimmune and other conditions in which K_V1.3 is upregulated and is therefore a potential therapeutic target, combined with the fact that many venom-derived peptides are potent inhibitors of K_V1.3, suggests that venoms are likely to continue to serve as a rich source of new pharmacological tools and therapeutic leads targeting this channel.

Immune system and cholangiocytes: A puzzling affair in primary biliary cholangitis

Primary biliary cholangitis (PBC) is a cholestatic liver disease characterized by the destruction of the small and medium bile ducts. Its pathogenesis is still unknown. Despite the genome wide association study findings, the therapies targeting the cytokines pathway, tested so far, have failed. The concept of the biliary epithelium as a key player of the PBC pathogenesis has emerged over the last few years. It is now well accepted that the biliary epithelial cells (BECs) actively participate to the genesis of the damage. The chronic stimulation of BECs via microbes and bile changes the cell phenotype toward an active state, which, across the production of proinflammatory mediators, can recruit, retain, and activate immune cells. The consequent immune system activation can in turn damage BECs. Thus, the crosstalk between both innate and adaptive immune cells and the biliary epithelium creates a paracrine loop responsible for the disease progression. In this review, we summarize the evidence provided in literature about the role of BECs and the immune system in the pathogenesis of PBC. We also dissect the relationship between the immune system and the BECs, focusing on the unanswered questions and the future potential directions of the translational research and the cellular therapy in this area.

The challenges of primary biliary cholangitis: What is new and what needs to be done

Primary Biliary Cholangitis (PBC) is an uncommon, chronic, cholangiopathy of autoimmune origin and unknown etiology characterized by positive anti-mitochondrial autoantibodies (AMA), female preponderance and progression to cirrhosis if left untreated. The diagnosis is based on AMA- or PBC-specific anti-nuclear antibody (ANA)-positivity in the presence of a cholestatic biochemical profile, histologic confirmation being mandatory only in seronegative cases. First-line treatment is ursodeoxycholic acid (UDCA), which is effective in preventing disease progression in about two thirds of the patients. The only approved second-line treatment is obeticholic acid. This article summarizes the most relevant conclusions of a meeting held in Lugano, Switzerland, from September 23rd-25th 2018, gathering basic and clinical scientists with various background from around the world to discuss the latest advances in PBC research. The meeting was dedicated to Ian Mackay, pioneer in the field of autoimmune liver diseases. The role of liver histology needs to be reconsidered: liver pathology consistent with PBC in AMA-positive individuals without biochemical cholestasis is increasingly reported, raising the question as to whether biochemical cholestasis is a reliable disease marker for both clinical practice and trials. The urgent need for new biomarkers, including more accurate markers of cholestasis, was also widely discussed during the meeting. Moreover, new insights in interactions of bile acids with biliary epithelia in PBC provide solid evidence of a role for impaired epithelial protection against potentially toxic hydrophobic bile acids, raising the fundamental question as to whether this bile acid-induced epithelial damage is the cause or the consequence of the autoimmune attack to the biliary epithelium. Strategies are needed to identify difficult-to-treat patients at an early disease stage, when new therapeutic approaches targeting immunologic pathways, in addition to bile acid-based therapies, may be effective. In conclusion, using interdisciplinary approaches, groundbreaking advances can be expected before long in respect to our understanding of the etiopathogenesis of PBC, with the ultimate aim of improving its treatment.

Cholangiocyte pathobiology

Cholangiocytes, the epithelial cells lining the intrahepatic and extrahepatic bile ducts, are highly specialized cells residing in a complex anatomic niche where they participate in bile production and homeostasis. Cholangiocytes are damaged in a variety of human diseases termed cholangiopathies, often causing advanced liver failure. The regulation of cholangiocyte transport properties is increasingly understood, as is their anatomical and functional heterogeneity along the biliary tract. Furthermore, cholangiocytes are pivotal in liver regeneration, especially when hepatocyte regeneration is compromised. The role of cholangiocytes in innate and adaptive immune responses, a critical subject relevant to immune-mediated cholangiopathies, is also emerging. Finally, reactive ductular cells are present in many cholestatic and other liver diseases. In chronic disease states, this repair response contributes to liver inflammation, fibrosis and carcinogenesis and is a subject of intense investigation. This Review highlights advances in cholangiocyte research, especially their role in development and liver regeneration, their functional and biochemical heterogeneity, their activation and involvement in inflammation and fibrosis and their engagement with the immune system. We aim to focus further attention on cholangiocyte pathobiology and the search for new disease-modifying therapies targeting the cholangiopathies.

Immunological abnormalities in patients with primary biliary cholangitis

Primary biliary cholangitis (PBC), an autoimmune liver disease occurring predominantly in women, is characterized by high titers of serum anti-mitochondrial antibodies (AMAs) and progressive intrahepatic cholestasis. The immune system plays a critical role in PBC pathogenesis and a variety of immune cell subsets have been shown to infiltrate the portal tract areas of patients with PBC. Amongst the participating immune cells, CD4 T cells are important cytokine-producing cells that foster an inflammatory microenvironment. Specifically, these cells orchestrate activation of other immune cells, including autoreactive effector CD8 T cells that cause biliary epithelial cell (BEC) injury and B cells that produce large quantities of AMAs. Meanwhile, other immune cells, including dendritic cells (DCs), natural killer (NK) cells, NKT cells, monocytes, and macrophages are also important in PBC pathogenesis. Activation of these cells initiates and perpetuates bile duct damage in PBC patients, leading to intrahepatic cholestasis, hepatic damage, liver fibrosis, and eventually cirrhosis or even liver failure. Taken together, the body of accumulated clinical and experimental evidence has enhanced our understanding of the immunopathogenesis of PBC and suggests that immunotherapy may be a promising treatment option. Herein, we summarize current knowledge regarding immunological abnormalities of PBC patients, with emphasis on underlying pathogenic mechanisms. The differential immune response which occurs over decades of disease activity suggests that different therapies may be needed at different stages of disease.

A Mouse Model of Autoimmune Cholangitis via Syngeneic Bile Duct Protein Immunization

Primary biliary cholangitis (PBC) is an autoimmune liver disease characterized by the destruction of interlobular biliary ductules, which progressively leads to cholestasis, hepatic fibrosis, cirrhosis, and eventually liver failure. Several mouse models have been used to clarify the pathogenesis of PBC and are generally considered reflective of an autoimmune cholangitis. Most models focus on issues of molecular mimicry between the E2 subunit of the pyruvate dehydrogenase complex (PDC-E2), the major mitochondrial autoantigen of PBC and xenobiotic cross reactive chemicals. None have focused on the classic models of breaking tolerance, namely immunization with self-tissue. Here, we report a novel mouse model of autoimmune cholangitis via immunization with syngeneic bile duct protein (BDP). Our results demonstrate that syngeneic bile duct antigens efficiently break immune tolerance of recipient mice, capturing several key features of PBC, including liver-specific inflammation focused on portal tract areas, increased number and activation state of CD4 and CD8 T cells in the liver and spleen. Furthermore, the germinal center (GC) responses in the spleen were more enhanced in our mouse model. Finally, these mice were 100% positive for anti-mitochondrial antibodies (AMAs). In conclusion, we developed a novel mouse model of PBC that may help to elucidate the detailed mechanism of this complex disease.

Liver damage in primary biliary cirrhosis and accompanied by primary Sjögren's syndrome: a retrospective pilot study

Introduction

Primary biliary cirrhosis (PBC) and primary Sjögren's syndrome (pSS) have been referred to as “generalized autoimmune epithelitis”. Indeed, the pathogenic mechanisms, clinical features, and optimal therapeutic approaches for them are not yet fully defined.

Material and methods

A retrospective analysis was carried out on clinical data obtained from 302 inpatients newly diagnosed with PBC, pSS, or the coexistence of PBC and SS between May 2011 and December 2014. Forty-two patients with abnormal hepatic function were divided into the PBC group (n = 17), the coexistent group (PBC accompanied by SS, n = 13), and the pSS group (n = 12). Their clinical symptoms, laboratory data, and pathological features were collected and analyzed when they were first diagnosed. The clinical and laboratory data were collected at 0, 1, and 3 months after treatment.

Results

Of the 42 patients with abnormal liver function, 4 were male and 38 were female patients. Compared with the patients in the PBC group, the patients in the other 2 groups were more likely to have an elevated erythrocyte sedimentation rate (ESR) and serum immunoglobulin G (IgG) levels. Abnormal serum immunoglobulin M levels (IgM) were more frequent in the PBC group. Corticosteroids were effective in normalizing elevated liver enzyme levels in patients with SS and in those with coexistent conditions.

Conclusions

This pilot study suggests that patients with PBC, pSS, and PBC/SS coexistence and having liver function abnormality share similar symptoms, but have different pathogenesis and prognosis.

It is time to change primary biliary cirrhosis (PBC): New nomenclature from "cirrhosis" to "cholangitis", and upcoming treatment based on unveiling pathology

Primary biliary cirrhosis (PBC) is a chronic, organ-specific, autoimmune liver disease characterized by progressive cholestasis, eventually leading to cirrhosis. Several lines of evidence have revealed a crucial role of adaptive as well as innate immune responses in the etiopathogenesis of PBC, and more recently, the biology of bile duct cells and genome-wide association studies (GWAS) demonstrated several key molecules and pathways in this enigmatic disease. Although ursodeoxycholic acid (UDCA) has been the only approved drug for PBC with clinical evidences for improvement of long-term outcomes, a substantial population have suboptimal responses to UDCA, resulting in unfavorable outcomes. In this regard, second-line treatment for patients refractory to UDCA is strongly awaited. In Japan, bezafibrate (BF) has been frequently used for this purpose, yet recent clinical trials failed to clearly demonstrate clinical efficacy of BF. Novel pharmacotherapies targeted to key molecules and pathways in PBC are upcoming. Finally, we sincerely call on all members of the Japan Society of Hepatology to use from this moment on the name "primary biliary cholangitis" for the disease known by its abbreviation PBC, in keeping with a very recent global agreement.

Understanding autoimmunity: The ion channel perspective

Ion channels are integral membrane proteins that orchestrate the passage of ions across the cell membrane and thus regulate various key physiological processes of the living system. The stringently regulated expression and function of these channels hold a pivotal role in the development and execution of various cellular functions. Malfunction of these channels results in debilitating diseases collectively termed channelopathies. In this review, we highlight the role of these proteins in the immune system with special emphasis on the development of autoimmunity. The role of ion channels in various autoimmune diseases is also listed out. This comprehensive review summarizes the ion channels that could be used as molecular targets in the development of new therapeutics against autoimmune disorders.

Primary biliary cirrhosis: From bench to bedside

Primary biliary cirrhosis (PBC) is a chronic non-suppurative destructive intrahepatic cholangitis leading to cirrhosis after a protractive non cirrhotic stage. The etiology and pathogenesis are largely unknown and autoimmne mechanisms have been implicated to explain the pathological lesions. Many epitopes and autoantigens have been reported as crucial in the pathophysiology of the disease and T and B cells abnormalities have been described, the exact pathways leading to the destruction of small intrahepatic ductules are mostly speculative. In this review we examined the various epidemiologal and geoepidemiological data as well as the complex pathogenetic aspects of this disease, focusing on recent in vivo and in vitro studies in this field. Initiation and progression of PBC is believed to be a multifactorial process with strong infuences from the patient’s genetic background and by various environmental factors. The role of innate and adaptive immunity, including cytokines, chemokines, macrophages and the involvement of apoptosis and reactive oxygen species are outlined in detailed. The current pathogenetic aspects are presented and a novel pathogenetic theory unifying the accumulated clinical information with in vitro and in vivo data is formulated. A review of clinical manifestations and immunological and pathological diagnosis was presented. Treatment modalities, including the multiple mechanisms of action of ursodeoxycholate were finally discussed.

Functional and structural features of cholangiocytes in health and disease

Cholangiocytes are the epithelial cells that line the bile ducts. Along the biliary tree, two different kinds of cholangiocytes exist; small and large cholangiocytes. Each type has important differences in their biological role in physiological and pathological conditions. In response to injury, cholangiocytes become reactive and acquire a neuroendocrine-like phenotype with the secretion of a number of peptides. These molecules act in an autocrine/paracrine fashion to modulate cholangiocyte biology and determine the evolution of biliary damage. The failure of such mechanisms is believed to influence the progression of cholangiopathies, a group of diseases that selectively target biliary cells. Therefore, the understanding of mechanisms regulating cholangiocyte response to injury is expected to foster the development of new therapeutic options to treat biliary diseases. In the present review, we will discuss the most recent findings in the mechanisms driving cholangiocyte adaptation to damage, with particular emphasis on molecular pathways that are susceptible of therapeutic intervention. Morphogenic pathways (Hippo, Notch, Hedgehog), which have been recently shown to regulate biliary ontogenesis and response to injury, will also be reviewed. In addition, the results of ongoing clinical trials evaluating new drugs for the treatment of cholangiopathies will be discussed.

Ion channels in innate and adaptive immunity

Ion channels and transporters mediate the transport of charged ions across hydrophobic lipid membranes. In immune cells, divalent cations such as calcium, magnesium, and zinc have important roles as second messengers to regulate intracellular signaling pathways. By contrast, monovalent cations such as sodium and potassium mainly regulate the membrane potential, which indirectly controls the influx of calcium and immune cell signaling. Studies investigating human patients with mutations in ion channels and transporters, analysis of gene-targeted mice, or pharmacological experiments with ion channel inhibitors have revealed important roles of ionic signals in lymphocyte development and in innate and adaptive immune responses. We here review the mechanisms underlying the function of ion channels and transporters in lymphocytes and innate immune cells and discuss their roles in lymphocyte development, adaptive and innate immune responses, and autoimmunity, as well as recent efforts to develop pharmacological inhibitors of ion channels for immunomodulatory therapy.

The intestinal microbiota and microenvironment in liver

The intestinal microbiome plays a significant role in the development of autoimmune diseases, in particular, inflammatory bowel diseases. But the interplay between the intestinal tract and the liver may explain the increased association with autoimmune liver diseases and inflammatory bowel diseases. The gut-liver axis involves multiple inflammatory cell types and cytokines, chemokines and other molecules which lead to the destruction of normal liver architecture. Triggers for the initiation of these events are unclear, but appear to include multiple environmental factors, including pathogenic or even commensal microbial agents. The variation in the gut microbiome has been cited as a major factor in the pathogenesis of autoimmune liver disease and even other autoimmune diseases. The unique positioning of the liver at the juncture of the peripheral circulation and the portal circulation augments the interaction between naïve T cells and other hepatic cells and leads to the disruption in the development of tolerance to commensal bacteria and other environmental agents. Finally, the innate immune system and in particular toll-like receptors play a significant role in the pathogenesis of autoimmune liver disease.

Antimitochondrial antibody recognition and structural integrity of the inner lipoyl domain of the E2 subunit of pyruvate dehydrogenase complex

Antimitochondrial autoantibodies (AMAs), the serological hallmark of primary biliary cirrhosis, are directed against the lipoyl domain of the E2 subunit of pyruvate dehydrogenase (PDC-E2). However, comprehensive analysis of the amino acid residues of PDC-E2 lipoyl β-sheet with AMA specificity is lacking. In this study, we postulated that specific residues within the lipoyl domain are critical to AMA recognition by maintaining conformational integrity. We systematically replaced each of 19 residue peptides of the inner lipoyl domain with alanine and analyzed these mutants for reactivities against 60 primary biliary cirrhosis and 103 control sera. Based on these data, we then constructed mutants with two, three, or four replacements and, in addition, probed the structure of the substituted domains using thiol-specific spin labeling and electron paramagnetic resonance (EPR) of a (5)Ile→Ala and (12)Ile→Ala double mutant. Single alanine replacement at (5)Ile, (12)Ile, and (15)Glu significantly reduced AMA recognition. In addition, mutants with two, three, or four replacements at (5)Ile, (12)Ile, and (15)Glu reduced AMA reactivity even further. Indeed, EPR reveals a highly flexible structure within the (5)Ile and (12)Ile double-alanine mutant. Autoreactivity is largely focused on specific residues in the PDC-E2 lipoyl domain critical in maintaining the lipoyl loop conformation necessary for AMA recognition. Collectively, the AMA binding studies and EPR analysis demonstrate the necessity of the lipoyl β-sheet structural conformation in anti-PDC-E2 recognition.

Targeting potassium channels Kv1.3 and KC a 3.1: routes to selective immunomodulators in autoimmune disorder treatment?

The Kv1.3 and KC a 3.1 potassium channels are promising targets for the treatment of autoimmune disorders. Many Kv1.3 and KC a 3.1 blockers have a more favorable adverse event profiles than existing immunosuppressants, suggesting the selectivity of Kv1.3 and KC a 3.1 blockade. The Kv1.3 and KC a 3.1 blockers exert differential effects in different autoimmune diseases. The Kv1.3 inhibitors or gene deletion have been shown to have benefits in multiple sclerosis, type 1 diabetes, rheumatoid arthritis, psoriasis, and rapidly progressive glomerulonephritis. The KC a 3.1 blockers have demonstrated efficacy in human primary biliary cirrhosis and showed protective effects in animal models of severe colitis, allergic encephalomyelitis, inflammatory bowel disease, and multiple sclerosis. The KC a 3.1 blockers are not considered candidates for treatment of multiple sclerosis. The selective immunosuppressive effects of the Kv1.3 and KC a 3.1 blockers are due to the differences in their distribution on autoimmune-related immune cells and tissues and β1 integrin (very late activating antigen)-Kv1.3 channel cross-talk.

The role of vitamin d in primary biliary cirrhosis: possible genetic and cell signaling mechanisms

Primary biliary cirrhosis (PBC) is an immune-mediated chronic inflammatory disease of the liver of unknown etiology. Vitamin D deficiency is highly prevalent in patients with PBC, and many studies have demonstrated the significant effect of calcitriol on liver cell physiology. Vitamin D has antiproliferative and antifibrotic effects on liver fibrosis. Genetic studies have provided an opportunity to determine which proteins link vitamin D to PBC pathology (e.g., the major histocompatibility complex class II molecules, the vitamin D receptor, toll-like receptors, apolipoprotein E, Nramp1, and cytotoxic T lymphocyte antigen-4). Vitamin D also exerts its effect on PBC through cell signaling mechanisms, that is, matrix metalloproteinases, prostaglandins, reactive oxygen species, and the transforming growth factor betas. In conclusion, vitamin D may have a beneficial role in the treatment of PBC. The best form of vitamin D for use in the PBC is calcitriol because it is the active form of vitamin D3 metabolite, and its receptors are present in the sinusoidal endothelial cells, Kupffer cells, and stellate cells of normal livers, as well as in the biliary cell line.

Analysis of altered microRNA expression profiles in peripheral blood mononuclear cells from patients with primary biliary cirrhosis

BACKGROUND AND AIM

MicroRNA, as an important regulator of gene expression, has been found to be associated with several diseases. MicroRNA expression profiles have been identified in several autoimmune diseases, such as rheumatoid arthritis, systemic lupus erythematosus, and multiple sclerosis. However, the expression profile in peripheral blood mononuclear cells (PBMCs) from primary biliary cirrhosis (PBC) patients and the role of microRNA in PBC remained unclear. The present study aimed to explore abnormal microRNA regulation in PBC.

METHODS

MicroRNA array was performed in PBMCs obtained from PBC patients versus healthy controls. Then, six of the 17 differentially expressed microRNAs were confirmed using quantitative real-time polymerase chain reaction. Based on bioinformatics analysis, we identified the potential biological processes and significant signaling pathways affected by these microRNAs, and generated the microRNA-gene network.

RESULTS

According to microRNA array, a total of 17 microRNAs were found to be differentially expressed. Six microRNAs have been validated using quantitative real-time polymerase chain reaction, and the results were consistent with microRNA array analysis. The bioinformatics analysis showed that the potential target genes of these microRNAs were involved in cell proliferation, cell differentiation, apoptosis, and signal transduction. Similarly, these microRNAs also affected endocytosis, mitogen-activated protein kinase signaling pathway, transforming growth factor-β signaling pathway, Wnt signaling pathway, calcium signaling pathway, etc.

CONCLUSION

In the present study, 17 microRNAs were identified to be differentially expressed in PBMCs from PBC patients. Functional bioinformatics analysis demonstrated that prediction genes targeted by these microRNAs were involved in multiple biological processes and signaling pathways. The present study offers intriguing new perspectives on the involvement of microRNA in PBC, but the precise mechanisms need to be validated further.

Autoantibodies in liver disease: important clues for the diagnosis, disease activity and prognosis

It has been well established that numerous kinds of autoantibodies have been detected in liver disease. Some kinds of autoantibodies may be helpful in the diagnosis of autoimmune liver diseases including autoimmune hepatitis, primary biliary cirrhosis or primary sclerosing cholangitis. However, these autoantibodies are present even in sera of patients with viral hepatitis, drug-induced hepatitis, alcoholic liver disease, non-alcoholic fatty liver disease and hepatocelluar carcinoma as well as in sera of patients with autoimmune liver diseases. Other kinds of autoantibodies are recognized as predictive hallmarks for disease activity or prognosis in liver diseases. On the other hand, treatment with interferon initiates the production of several types of autoantibodies in patients with chronic hepatitis C virus infection. Some of autoantibodies induced by interferon may postulate the treatment outcome in those patients. Recent studies also revealed the close correlation between oxidative stress and the production of autoantibodies in liver diseases. This article primarily reviews the recent advances of autoantibodies in the liver diseases and discusses the clinical significance of these autoantibodies.

Environment and primary biliary cirrhosis: electrophilic drugs and the induction of AMA

Environmental stimulation is a major factor in the initiation and perpetuation of autoimmune diseases. We have addressed this issue and focused on primary biliary cirrhosis (PBC), an autoimmune disease of the liver. Immunologically, PBC is distinguished by immune mediated destruction of the intra hepatic bile ducts and the presence of high titer antimitochondrial autoantibodies (AMA) directed against a highly specific epitope within the lipoic acid binding domain of the pyruvate dehydrogenase E2 subunit (PDC-E2). We submit that the uniqueness of AMA epitope specificity and the conformational changes of the PDC-E2 lipoyl domain during physiological acyl transfer could be the lynchpin to the etiology of PBC and postulate that chemical xenobiotics modification of the lipoyl domain of PDC-E2 is sufficient to break self-tolerance, with subsequent production of AMA in patients with PBC. Indeed, using quantitative structure activity relationship (QSAR) analysis on a peptide-xenobiotic conjugate microarray platform, we have demonstrated that when the lipoyl domain of PDC-E2 was modified with specific synthetic small molecule lipoyl mimics, the ensuing structures displayed highly specific reactivity to PBC sera, at levels often higher than the native PDC-E2 molecule. Hereby, we discuss our recent QSAR analysis data on specific AMA reactivity against a focused panel of lipoic acid mimic in which the lipoyl di-sulfide bond are modified. Furthermore, data on the immunological characterization of antigen and Ig isotype specificities against one such lipoic acid mimic; 6,8-bis(acetylthio)octanoic acid (SAc), when compared with rPDC-E2, strongly support a xenobiotic etiology in PBC. This observation is of particular significance in that approximately one third of patients who have taken excessive acetaminophen (APAP) developed AMA with same specificity as patients with PBC, suggesting that the lipoic domain are a target of APAP electrophilic metabolites such as NAPQI. We submit that in genetically susceptible hosts, electrophilic modification of lipoic acid in PDC-E2 by acetaminophen or similar drugs can facilitate loss of tolerance and lead to the development of PBC.

Toll-like receptors in liver disease

Activation of inflammatory signaling pathways is of central importance in the pathogenesis of alcoholic liver disease (ALD) and nonalcoholic steatohepatitis (NASH). Recent studies demonstrated that Toll-like receptors, the sensors of microbial and endogenous danger signals, are expressed and activated in innate immune cells as well as in parenchymal cells in the liver and thereby contribute to ALD and NASH. In this review, we emphasize the importance of gut-derived endotoxin and its recognition by TLR4 in the liver. The significance of TLR-induced intracellular signaling pathways and cytokine production as well as the contribution of individual cell types to the inflammation is evaluated. The contribution of TLR signaling to the induction of liver fibrosis and to the progression of liver pathology mediated by viral pathogens is reviewed in the context of ALD and NASH.

Role of autoimmunity in primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is an autoimmune liver disease characterized by the presence of serum autoantibodies and chronic nonsuppurative destructive cholangitis. The pathogenesis of PBC involves environmental factors, genetic predisposition and loss of immune tolerance. In recent years, it has become univocally accepted that an inappropriately activated immune response is one of the most important factors in PBC. In this study, the role of autoimmunity in PBC is summarized and a feasible research orientation is recommended.

Hepatic expression of toll-like receptors 3, 4, and 9 in primary biliary cirrhosis and chronic hepatitis C

Toll-like receptors (TLRs) may play a role in the inflammatory patterns observed in primary biliary cirrhosis (PBC) and chronic hepatitis C (CHC). We investigated TLR 3, 4 and 9 expression in PBC and CHC using immunohistochemical staining.

METHODS

Patient biopsies of PBC (N=11) and CHC (N=15) were compared to disease free livers (n=7). The extent of TLR staining was assessed separately according to a semi-quantitative scale for hepatocytes, cholangiocytes and portal mononuclear cells (PMC).

RESULTS

In hepatocytes, TLR4 expression was increased (PBC; P=0.019), as was TLR9 (PBC; P=0.006, CHC; P=0.001). Cholangiocyte expression of TLRs 4 and 3 was reduced in both PBC (TLR4; P<0.0001, TLR3; P=0.006) and CHC (TLR4; P<0.0001, TLR3; P=0.014). Cholangiocyte expression of TLR9 was elevated for both groups and was significant in CHC (P=0.0115). PMCs showed up-regulation of TLR9 in PBC (P=0.022) and CHC (P=0.0001), with almost no expression of TLR 3 or 4.

CONCLUSIONS

In PBC and CHC, hepatocytes showed increased TLR 4 and 9 expression without change in TLR3. Cholangiocytes showed increased TLR9 expression as opposed to down-regulation of TLRs 3 and 4. PMCs in both diseases had significantly increased TLR 9 expression perhaps implicating TLR9 expression in chronic liver inflammation.

Xenobiotics and autoimmunity: does acetaminophen cause primary biliary cirrhosis?

The serologic hallmark of primary biliary cirrhosis (PBC) is the presence of antimitochondrial autoantibodies (AMAs) directed against the E2 subunit of the pyruvate dehydrogenase complex (PDC-E2). The PBC-related autoepitope of PDC-E2 contains lipoic acid, and previous work has demonstrated that mimics of lipoic acid following immunization of mice lead to a PBC-like disease. Furthermore, approximately one-third of patients who have ingested excessive amounts of acetaminophen (paracetamol) develop AMA of the same specificity as patients with PBC. Quantitative structure-activity relationship (QSAR) data indicates that acetaminophen metabolites are particularly immunoreactive with AMA, and we submit that in genetically susceptible hosts, electrophilic modification of lipoic acid in PDC-E2 by acetaminophen or similar drugs can facilitate a loss of tolerance and lead to the development of PBC.

Involvement of commensal bacteria may lead to dysregulated inflammatory and autoimmune responses in a mouse model for chronic nonsuppurative destructive cholangitis

BACKGROUND

We previously reported a mouse model of primary biliary cirrhosis (PBC)-like chronic nonsuppurative destructive cholangitis (CNSDC), in which frequent injections of Streptococcus intermedius induced CNSDC and autoantibody production. The present study was performed to verify the model by examining 1) the reappearance of the PBC-like CNSDC after lymphocyte transfer from model to naïve mice, 2) the involvement of autophagy, and 3) the influence of the strain difference.

METHODS

Mice were inoculated with S. intermedius weekly for 8 weeks, then sacrificed to obtain samples. Spleen cells obtained from S. intermedius-inoculated mice were transferred to RAG2(-/-) mice.

RESULTS

CNSDC and elevated serum level of anti-gp210 titers were observed in S. intermedius-inoculated C57BL/6 mice, similar to the results of our previous report using BALB/c mice. Portal inflammation was induced in the livers of RAG2(-/-) mice by the transfer of spleen cells from S. intermedius-inoculated C57BL/6 mice. Among the inflammatory cells in the RAG2(-/-) mice, CD3-positive cells were predominant. Autophagosome-like structures were detected histologically, in the cytoplasm of infiltrated cells around the bile ducts in the livers of S. intermedius-inoculated both C57BL/6 and BALB/c mice. In S. intermedius-inoculated C3H/HeJ mice, inflammation in the portal area was less extensive than that in the hepatic parenchyma.

CONCLUSION

Bacterial component(s) and sequentially upregulated innate and acquired immune responses, accompanied by autophagy, might trigger CNSDC, via autoimmune mechanisms. Throughout the generation of bacteria-triggered PBC-like CNSDC, strain difference may influence the response to S. intermedius-inoculation in the liver.

Toll-like receptors in liver fibrosis: cellular crosstalk and mechanisms

Toll-like receptors (TLRs) are pattern recognition receptors that distinguish conserved microbial products, also known as pathogen-associated molecular patterns (PAMPs), from host molecules. Liver is the first filter organ between the gastrointestinal tracts and the rest of the body through portal circulation. Thus, the liver is a major organ that must deal with PAMPs and microorganisms translocated from the intestine and to respond to the damage associated molecular patterns (DAMPs) released from injured organs. These PAMPs and DAMPs preferentially activate TLR signaling on various cell types in the liver inducing the production of inflammatory and fibrogenic cytokines that initiate and prolong liver inflammation, thereby leading to fibrosis. We summarize recent findings on the role of TLRs, ligands, and intracellular signaling in the pathophysiology of liver fibrosis due to different etiology, as well as to highlight the potential role of TLR signaling in liver fibrosis associated with hepatitis C infection, non-alcoholic and alcoholic steatoheoatitis, primary biliary cirrhosis, and cystic fibrosis.

Etiopathogenesis of primary biliary cirrhosis: an overview of recent developments

Substantial advancements in the field of primary biliary cirrhosis (PBC) research have broadened our understanding of this enigmatic disease. Genome-wide studies have identified several new candidate genes involved in the immunoregulatory process, particularly those responsible for antigen presentation and lymphocyte signaling. Examples include the HLA class-II region and genes implicated in IL12-JAK/STAT signaling, and the NF-κB and TNF signaling pathways. Environmental triggers appear to disrupt the pre-existing, unstable immune tolerance in genetically susceptible individuals, and molecular mimics of the PBC-specific autoantigen (PDC) may be derived from microbes or xenobiotic compounds, which modify native proteins, making them immunogenic. Although the vast majority of patients with PBC are AMA-positive, a variety of disease-specific antinuclear antibodies have been recognized in conferring a worse clinical outcome. There has also been a revived interest in the role of antibody-secreting B cells in murine models suggesting that depletion of these cells paradoxically exacerbates cholangiopathy. Biliary specificity in PBC is most likely driven by the uniqueness of cholangiocyte apoptosis in which the PDC-E2 autoantigen undergoes differential glutathiolation. Cholangiocytes also possess the ability to phagocytose neighboring apoptotic cells, present intact immunoreactive antigen, and undergo attack from autoantibodies, the innate immune system, and autoreactive lymphocytes. Cellular senescence and a lack of functioning T-regulatory cells are proposed mechanisms by which this multi-lineage process is thought to be enhanced. This review summarizes these key advances as the true complexities of the disease process begin to be unraveled.

Are dysregulated inflammatory responses to commensal bacteria involved in the pathogenesis of hepatobiliary-pancreatic autoimmune disease? An analysis using mice models of primary biliary cirrhosis and autoimmune pancreatitis

The etiopathogenesis of many autoimmune disorders has not been identified. The aim of this paper is to focus on the involvement of bacterial exposure in the pathogenesis of primary biliary cirrhosis (PBC) and autoimmune pancreatitis (AIP), both of which are broadly categorized as autoimmune disorders involving hepatobiliary-pancreatic lesions. Avirulent and/or commensal bacteria, which may have important role(s) as initiating factors in the pathogenesis of autoimmune disorders such as PBC and AIP, will be emphasized.

Type I interferons protect from Toll-like receptor 9-associated liver injury and regulate IL-1 receptor antagonist in mice

BACKGROUND & AIMS

Liver inflammation and injury are mediated by the innate immune response, which is regulated by Toll-like receptors (TLR). Activation of TLR9 induces type I interferons (IFNs) via the interferon regulatory factor (IRF)-7. We investigated the roles of type I IFNs in TLR9-associated liver injury.

METHODS

Wild-type (WT), IRF7-deficient, and IFN-α/β receptor 1 (IFNAR1)-deficient mice were stimulated with TLR9 or TLR2 ligands. Findings from mice were verified in cultured hepatocytes and liver mononuclear cells (LMNCs) as well as in vivo experiments using recombinant type I IFN and interleukin-1 receptor antagonist (IL-1ra).

RESULTS

Type I IFNs were up-regulated during TLR9-associated liver injury in WT mice. IRF7- and IFNAR1-deficient mice, which have disruptions in type I IFN production or signaling, respectively, had increased liver damage and inflammation, decreased recruitment of dendritic cells, and increased production of tumor necrosis factor α by LMNCs. These findings indicate that type I IFNs have anti-inflammatory activities in liver. IL-1ra, which is produced by LMNCs and hepatocytes, is an IFN-regulated antagonist of the proinflammatory cytokine IL-1β; IRF7- and IFNAR1-deficient mice had decreased levels of IL-1ra compared with WT mice. IL-1ra protected cultured hepatocytes from IL-1β-mediated sensitization to cytotoxicity from tumor necrosis factor α. In vivo exposure to type I IFN, which induced IL-1ra, or administration of IL-1ra reduced TLR9-associated liver injury; the protective effect of type I IFNs therefore appears to be mediated by IFN-dependent induction of IL-1ra.

CONCLUSIONS

Type I IFNs have anti-inflammatory effects mediated by endogenous IL-1ra, which regulates the extent of TLR9-induced liver damage. Type I IFN signaling is therefore required for protection from immune-mediated liver injury.

Pathogenesis of cholestatic liver disease and therapeutic approaches

Cholestatic liver disorders are caused by genetic defects, mechanical aberrations, toxins, or dysregulations in the immune system that damage the bile ducts and cause accumulation of bile and liver tissue damage. They have common clinical manifestations and pathogenic features that include the responses of cholangiocytes and hepatocytes to injury. We review the features of bile acid transport, tissue repair and regulation, apoptosis, vascular supply, immune regulation, and cholangiocytes that are associated with cholestatic liver disorders. We now have a greater understanding of the physiology of cholangiocytes at the cellular and molecular levels, as well as genetic factors, repair pathways, and autoimmunity mechanisms involved in the pathogenesis of disease. These discoveries will hopefully lead to new therapeutic approaches for patients with cholestatic liver disease.

The autoimmunity of primary biliary cirrhosis and the clonal selection theory

Primary biliary cirrhosis (PBC) is a chronic cholestatic liver disease in which an immune-mediated injury targets the small intrahepatic bile ducts. PBC is further characterized by highly specific serum antimitochondrial autoantibodies (AMA) and autoreactive T cells, a striking female predominance, a strong genetic susceptibility, and a plethora of candidate environmental factors to trigger the disease onset. For these reasons PBC appears ideal to represent the developments of the clonal selection theory over the past decades. First, a sufficiently potent autoimmunogenic stimulus in PBC would require the coexistence of numerous pre-existing conditions (mostly genetic, as recently illustrated by genome-wide association studies and animal models) to perpetuate the destruction of the biliary epithelium by the immune system via the persistence of forbidden clones. Second, the proposed modifications of mitochondrial autoantigens caused by infectious agents and/or xenobiotics well illustrate the possibility that peculiar changes in the antigen structure and flexibility may contribute to tolerance breakdown. Third, the unique apoptotic features demonstrated for cholangiocytes are the ideal setting for the development of mitochondrial autoantigen presentation to the immune system through macrophages and AMA thus turning the non traditional mitochondrial antigen into a traditional one. This article will review the current knowledge on PBC etiology and pathogenesis in light of the clonal selection theory developments.

Update on primary biliary cirrhosis

Primary biliary cirrhosis is an autoimmune chronic liver disease characterized by progressive bile duct destruction eventually leading to cirrhosis, liver failure, and death. The autoimmune pathogenesis is supported by a plethora of experimental and clinical data, such as the presence of autoreactive T cells and serum autoantibodies. The aetiology remains unknown, although evidence suggests a role for both genetic susceptibility and environmental factors that remain to be determined. In fact, a number of chemicals and infectious agents have been proposed to induce the disease in predisposed individuals. The recent availability of several murine models will significantly help in understanding pathophysiology mechanisms. In this review, we critically summarize the most recent data on the aetiopathogenesis of primary biliary cirrhosis, discuss the latest theories and developments, and suggest directions for future research.

Experimental evidence on the immunopathogenesis of primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is a chronic cholestatic liver disease for which an autoimmune pathogenesis is supported by clinical and experimental data, including the presence of autoantibodies and autoreactive T cells. The etiology remains to be determined, yet data suggest that both a susceptible genetic background and unknown environmental factors determine disease onset. Multiple infectious and chemical candidates have been proposed to trigger the disease in a genetically susceptible host, mostly by molecular mimicry. Most recently, several murine models have been reported, including genetically determined models as well as models induced by immunization with xenobiotics and bacteria.

Autoantibody IgG subclasses to recombinant antigens and the role of bacterial stimuli in primary biliary cirrhosis

AIM

Serum antimitochondrial antibody (AMA) of the IgG2 and IgG3 subclasses has been reported to be predominant in patients with primary biliary cirrhosis from developed countries. No data are available as to the significance of AMA subtypes in Japanese primary biliary cirrhosis (PBC) patients who have previously manifested unique serological features, nor it is known whether AMA subclasses are influenced by bacterial stimuli, as suggested by the molecular theory of PBC. We undertook a three-step study to address these questions.

METHODS

First, Japanese PBC sera were tested using the established triple recombinant antigen (pML-MIT3) to find AMA subclass distribution. Second, we used the three recombinant mitochondrial antigens in PBC sera of Japanese and USA patients to explore the ethnic difference. Third, we used CpG oligodeoxynucleotides and a B cell mitogen to challenge ex vivo peripheral leukocytes from indirect immunofluorescence (IIF)-AMA-positive patients with Japanese PBC.

RESULTS

We detected most frequently IgG2-AMA followed by IgG3-AMA, with the latter being more common in IIF-AMA-positive cases, and demonstrated that the IgG3 reactivity against the dominant antigen was significantly higher in PBC sera from the USA. We determined that the bacterial stimulus was superior to the mitogen at inducing a predominant production of IgG2-AMA and CD20+ B cell activation.

CONCLUSION

Our data cumulatively supported the hypothesis that IgG2 AMA subtypes are predominant in PBC and suggest that this might be favored by an innate immune reaction against bacterial particles, such as CpG DNA.

Toll-like receptors and their role in gastrointestinal disease

The innate immune response to invading pathogens is centred upon a family of non-clonal, germline-encoded pattern recognition receptors (PRRs), the Toll-like receptors (TLRs). These provide specificity for a vast range of microbial pathogens, and offer an immediate anti-microbial response system. Thirteen mammalian TLRs have been described; 10 are expressed in humans, each responsible for the recognition of distinct, invariant microbial structures originating from bacteria, viruses, fungi and protozoa. The two most thoroughly studied are TLR4 and TLR2, the PRRs for Gram-negative and Gram-positive bacterial products, respectively. TLR4 is also the major receptor recognising endogenous ligands released from damaged or dying cells. Activation of a TLR by its relevant ligand rapidly ignites a complex intracellular signaling cascade that ultimately results in upregulation of inflammatory genes and production of proinflammatory cytokines, interferons and recruitment of myeloid cells. It also stimulates expression, upon antigen presenting cells, of co-stimulatory molecules required to induce an adaptive immune response. Whilst a robust TLR response is critical for survival and defence against invading pathogens, inappropriate signaling in response to alterations in the local microflora environment can be detrimental. Such 'unhelpful TLR responses' could form the basis for a large number of gastrointestinal and liver disorders, including inflammatory bowel disease, viral hepatitis, autoimmune liver diseases and hepatic fibrosis. As our understanding of TLRs expands, the pathogenesis of a number of gastrointestinal disorders will be further elucidated, and this offers potential for specific therapies aimed directly at TLR signaling.

Liver architecture, cell function, and disease

The liver is an organ consisting of the largest reticulo-endothelial cell network in the body and playing an important role in host defense against invading microorganisms. The organ is comprised of parenchymal cells and many different types of non-parenchymal cells, all of which play a significant role. Even biliary epithelial cells are not only the target in autoimmune liver diseases but also have central role in orchestrating several immune cells involved in both innate and acquired immunity. Tissue damage caused by various agents results in inflammation, necrosis, fibrosis, and, eventually, distortion of normal hepatic architecture, cirrhosis, and functional deterioration.

Bone marrow-derived immune cells mediate sensitization to liver injury in a myeloid differentiation factor 88-dependent fashion

Toll-like receptors (TLRs) expressed on both immune cells and hepatocytes recognize microbial danger signals and regulate immune responses. Previous studies showed that TLR9 and TLR2 mediate Propionibacterium acnes-induced sensitization to lipopolysaccharide-triggered acute liver injury in mice. Ligand-specific activation of TLR2 and TLR9 are dependent on the common TLR adaptor, myeloid differentiation factor 88 (MyD88). Here, we dissected the role of MyD88 in parenchymal and bone marrow (BM)-derived cells in liver sensitization. Using chimeric mice with green fluorescent protein-expressing BM cells, we identified that P. acnes-induced liver inflammatory foci are of BM origin. Chimeras with MyD88-deficient BM showed no inflammatory foci after P. acnes or TLR2+TLR9 challenge, suggesting that recruitment of inflammatory cells to the liver required MyD88 expression in BM-derived cells. Further, selective MyD88 deficiency in parenchymal cells in mice with wild-type BM failed to prevent inflammatory cell infiltration. These results demonstrate that MyD88 in immune cells rather than in liver parenchymal cells plays an important role in inflammatory cell recruitment and liver injury.

Toll-like receptors and adaptor molecules in liver disease: update

Toll-like receptors (TLRs) are pattern recognition receptors that recognize pathogen-associated molecular patterns and signal through adaptor molecules, myeloid differentiation factor 88 (MyD88), Toll/IL-1 receptor domain containing adaptor protein (TIRAP), Toll/IL-1 receptor domain containing adaptor inducing interferon-beta (TRIF), and TRIF-related adaptor molecule (TRAM) to activate transcription factors, nuclear factor (NF)-kappaB, activator protein 1 (AP-1), and interferon regulatory factors (IRFs) leading to the initiation of innate immunity. This system promptly initiates host defenses against invading microorganisms. Endogenous TLR ligands such as the products from dying cells may also engage with TLRs as damage-associated molecular patterns. Although Kupffer cells are considered the primary cells to respond to pathogen associated molecular patterns in the liver, recent studies provide evidence of TLR signaling in hepatic nonimmune cell populations, including hepatocytes, biliary epithelial cells, endothelial cells, and hepatic stellate cells. This review highlights advances in TLR signaling in the liver, the role of TLRs in the individual hepatic cell populations, and the implication of TLR signaling in acute and chronic liver diseases. We further discuss recent advances regarding cytosolic pattern recognition receptors, RNA helicases that represents a new concept in chronic hepatitis C virus infection.

Etiopathogenesis of primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is an autoimmune disease of the liver characterized by progressive bile duct destruction eventually leading to cirrhosis and liver failure. The serological hallmark of the disease is the presence of circulating antimitochondrial antibodies (AMA). These reflect the presence of autoreactive T and B cells to the culprit antigens, the E2 subunits of mitochondrial 2-oxo-acid dehydrogenase enzymes, chiefly pyruvate dehydrogenase (PDC-E2). The disease results from a combination of genetic and environmental risk factors. Genetic predisposition is indicated by the higher familial incidence of the disease particularly among siblings and the high concordance rate among monozygotic twins. Environmental triggering events appear crucial to disrupt a pre-existing unstable immune tolerance of genetic origin allowing, after a long latency, the emergence of clinical disease. Initiating mimotopes of the vulnerable epitope of the PDC-E2 autoantigen can be derived from microbes that utilize the PDC enzyme or, alternatively, environmental xenobiotics/chemical compounds that modify the structure of native proteins to make them immunogenic. A further alternative as a source of antigen is PDC-E2 derived from apoptotic cells. In the effector phase the biliary ductular cell, by reason of its proclivity to express the antigen PDC-E2 in the course of apoptosis, undergoes a multilineage immune attack comprised of CD4⁺ and CD8⁺ T cells and antibody. In this article, we critically review the available evidence on etiopathogenesis of PBC and present interpretations of complex data, new developments and theories, and nominate directions for future research.

A tribute to an outstanding immunologist - Ian Reay Mackay

The 11th Australasian Autoimmunity Workshop was held in Melbourne, Australia from July 6-8, 2007 organized by the Monash University Autoimmunity Network. The workshops, founded by the late Kevin Lafferty, are a chance for Australasians interested in research into autoimmune disease to present and discuss their work. This workshop also was a chance to acknowledge Ian Mackay, a pioneer clinician-scientist who has made major contributions to our understanding of autoimmune diseases. Friends, colleagues and former students attended the Workshop and acknowledged Ian's expertise and mentorship. This edition of the Journal of Autoimmunity pays tribute to Ian Mackay. It features articles from attendees at the workshop, and contributions from some of Ian's past students and past and current collaborators.