Patients with primary biliary cirrhosis react against a ubiquitous xenobiotic-metabolizing bacterium

Primary biliary cirrhosis and liver transplantation

Primary biliary cirrhosis (PBC) is an immune-mediated chronic progressive inflammatory liver disease, predominantly affecting middle-aged women, characterized by the presence of antimitochondrial antibodies (AMAs), which can lead to liver failure. Genetic contributions, environmental factors including chemical and infectious xenobiotics, autoimmunity and loss of tolerance have been aggressively investigated in the pathogenesis of PBC, however, the actual impact of these factors is still controversial. Survival of PBC patients has been largely improved with the widespread use of ursodeoxycholic acid (UDCA), however, one third of patients still do not respond to the treatment and proceed to liver cirrhosis, requiring liver transplantation as a last resort for cure. The outcome of liver transplantation is excellent with 5- and 10-year survival rates around 80% and 70%, respectively, while along with long survival, the recurrence of the disease has become an important outcome after liver transplantation. Prevalence rates of recurrent PBC rage widely between 1% and 35%, and seem to increase with longer follow-up. Center-specific issues, especially the use of protocol biopsy, affect the variety of incidence, yet, recurrence itself does not affect patient and graft survival at present, and retransplantation due to recurrent disease is extremely rare. With a longer follow-up, recurrent disease could have an impact on patient and graft survival.

Interplay between carbohydrate and lipid in recognition of glycolipid antigens by natural killer T cells

Natural killer T (NKT) cells are a T cell subpopulation that were named originally based on coexpression of receptors found on natural killer (NK) cells, cells of the innate immune system, and by T lymphocytes. The maturation and activation of NKT cells requires presentation of glycolipid antigens by CD1d, a cell surface protein distantly related to the major histocompatibility complex (MHC)-encoded antigen presenting molecules. This specificity distinguishes NKT cells from most CD4(+) and CD8(+) T cells that recognize peptides presented by MHC class I and class II molecules. The rapid secretion of a large amount of both Th1 and Th2 cytokines by activated NKT cells endows them with the ability to play a vital role in the host immune defense against various microbial infections. In this review, we summarize progress on identifying the sources of microbe-derived glycolipid antigens recognized by NKT cells and the biochemical basis for their recognition.

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.

Human leukocyte antigen class II molecules confer both susceptibility and progression in Japanese patients with primary biliary cirrhosis

Along with twin and family studies, recent genome-wide association studies suggest that genetic factors contribute to the susceptibility and severity of primary biliary cirrhosis (PBC). Although several reports have demonstrated that the human leukocyte antigen (HLA) DRB1*08:03 allele is associated with disease susceptibility in Japan, the precise analysis of HLA haplotypes and the role of amino acid alignment have not been fully clarified. We investigated HLA class I A, B, and C and HLA class II DRB1 and DQB1 alleles and haplotypes in 229 Japanese patients with PBC and compared them with the published data of 523 healthy subjects. Significant associations were found with PBC susceptibility for the DRB1*08:03-DQB1*06:01 (13% versus 6%; P = 0.000025; odds ratio [OR] = 2.22) and DRB1*04:05-DQB1*04:01 haplotypes (17% versus 13%; P = 0.044; OR = 1.38). Conversely, there were significant protective associations with the DRB1*13:02-DQB1*06:04 (2% versus 5%; P = 0.00093; OR = 0.27) and DRB1*11:01-DQB1*03:01 haplotypes (1% versus 4%; P = 0.03; OR = 0.37). The frequency of the DRB1*09:01-DQB1*03:03 haplotype was significantly higher in patients who had received orthotopic liver transplantation (33% versus 11%; P = 0.0012; OR = 3.96). Furthermore, the frequency of serine at position 57 (P = 0.0000015; OR = 1.83) of the DRβchain differed the most in patients with PBC, compared with healthy subjects.

CONCLUSION

This study established the role of HLA haplotypes in determining PBC susceptibility and progression in the Japanese population. Further resequencing of the HLA region is required to more precisely identify the genetic components of PBC.

Approaches to the pathogenesis of primary biliary cirrhosis through animal models

Primary biliary cirrhosis (PBC) is a chronic and progressive cholestatic liver disease of unknown etiopathogenesis that mainly affects middle-aged women. Patients show non-suppurative cholangitis with damage and destruction of the small- and medium-sized intrahepatic bile ducts. Characteristically, the disease is strongly associated with autoimmune phenomena such as the appearance of serum antimitochondrial autoantibodies (AMA) and portal infiltrating T cells against the inner lipoyl domain in the E2 component of the pyruvate dehydrogenase complex (PDC-E2). Here we review the major characteristics of a series of inducible and genetically modified animal models of PBC and analyze the similarities and differences to PBC features in humans.

Animal models of primary biliary cirrhosis: materials and methods

Primary biliary cirrhosis (PBC) is a female-predominant autoimmune disease of the liver characterized by immune-mediated destruction of the intrahepatic bile ducts and the presence of antimitochondrial antibodies (AMAs). There have been limited advances in understanding the molecular pathogenesis of the disease because of the difficulty in accessing human tissues and the absence of appropriate animal models. Recently, several unique murine models that manifest the serological, biochemical, and histological features similar to human PBC have been described. In this article, we discuss the current data on three spontaneous and two induced murine models of PBC. The spontaneous models are: (a) NOD.c3c4, (b) dominant negative TGF-β receptor II (dnTGFβRII), and (c) IL-2Rα(-/-) mouse line models. The two induced models are: (a) xenobiotic and (b) Novosphingobium aromaticivorans immunized mice. These animal models provide various important platforms to further investigate the etiology and mechanisms of pathogenesis in PBC. Laboratory methodologies and the protocols that are used in evaluating these animal models are described. Finally, we stress the importance of realizing the strengths and limitations of the animal models are essential in data analysis and their application in therapeutic studies.

Cholangiopathy with respect to biliary innate immunity

Biliary innate immunity is involved in the pathogenesis of cholangiopathies in cases of biliary disease. Cholangiocytes possess Toll-like receptors (TLRs) which recognize pathogen-associated molecular patterns (PAMPs) and play a pivotal role in the innate immune response. Tolerance to bacterial PAMPs such as lipopolysaccharides is also important to maintain homeostasis in the biliary tree, but tolerance to double-stranded RNA (dsRNA) is not found. Moreover, in primary biliary cirrhosis (PBC) and biliary atresia, biliary innate immunity is closely associated with the dysregulation of the periductal cytokine milieu and the induction of biliary apoptosis and epithelial-mesenchymal transition (EMT), forming in disease-specific cholangiopathy. Biliary innate immunity is associated with the pathogenesis of various cholangiopathies in biliary diseases as well as biliary defense systems.

Novel approach to bile duct damage in primary biliary cirrhosis: participation of cellular senescence and autophagy

Primary biliary cirrhosis (PBC) is characterized by antimitochondrial autoantibodies (AMAs) in patients' sera and histologically by chronic nonsuppurative destructive cholangitis in small bile ducts, eventually followed by extensive bile duct loss and biliary cirrhosis. The autoimmune-mediated pathogenesis of bile duct lesions, including the significance of AMAs, triggers of the autoimmune process, and so on remain unclear. We have reported that cellular senescence in biliary epithelial cells (BECs) may be involved in bile duct lesions and that autophagy may precede the process of biliary epithelial senescence in PBC. Interestingly, BECs in damaged bile ducts show characteristicsof cellular senescence and autophagy in PBC. A suspected causative factor of biliary epithelial senescence is oxidative stress. Furthermore, senescent BECs may modulate the microenvironment around bile ducts by expressing various chemokines and cytokines called senescence-associated secretory phenotypes and contribute to the pathogenesis in PBC.

Primary biliary cirrhosis and Sjögren's syndrome: autoimmune epithelitis

Primary biliary cirrhosis (PBC) has been often coined a model autoimmune disease based on the homogeneity amongst patients, the frequency and similarity of antimitochondrial antibodies, including the highly directed immune response to pyruvate dehydrogenase (PDC-E2). A significant number of patients with PBC suffer from sicca and amongst these, there are patients who also have classic Sjögren's syndrome. Indeed, both PBC and Sjögren's syndrome are characterized by inflammation of target epithelial elements. Both diseases can be considered on the basis of a number of other related clinical aspects, including proposed unique apoptotic features of the target tissue, the role of secretory IgA, and the frequency with which both diseases overlap with each other. Indeed, PBC may be considered a Sjögren's syndrome of the liver, whereas Sjögren's syndrome can be equally discussed as PBC of the salivary glands. Dissection of the genetic predispositions for both diseases and especially the molecular basis of effector mechanisms, will become critical elements in developing new therapies.

Immunopathogenesis of primary biliary cirrhosis: an old wives' tale

Primary biliary cirrhosis (PBC) is a cholestatic liver disease characterised by the autoimmune destruction of the small intrahepatic bile ducts. The disease has an unpredictable clinical course, but may progress to fibrosis and cirrhosis. Although medical treatment with urseodeoxycholic acid is largely successful, some patients may progress to liver failure requiring liver transplantation. PBC is characterised by the presence of disease specific anti-mitochondrial (AMA) antibodies, which are pathognomonic for PBC development. The disease demonstrates an overwhelming female preponderance and virtually all women with PBC present in middle age. The reasons for this are unknown; however several environmental and immunological factors may be involved. As the immune systems ages, it become less self tolerant, and mounts a weaker response to pathogens, possibly leading to cross reactivity or molecular mimicry. Some individuals display immunological changes which encourage the development of autoimmune disease. Risk factors implicated in PBC include recurrent urinary tract infection in females, as well as an increased prevalence of reproductive complications. These risk factors may work in concert with and possibly even accelerate, immune system ageing, contributing to PBC development. This review will examine the changes that occur in the immune system with ageing, paying particular attention to those changes which contribute to the development of autoimmune disease with increasing age. The review also discusses risk factors which may account for the increased female predominance of PBC, such as recurrent UTI and oestrogens.

Seasonal variation in the patient diagnosis of primary biliary cirrhosis: further evidence for an environmental component to etiology

The etiology of primary biliary cirrhosis (PBC) is far from clear. Both genetic and environmental factors are likely to be involved. We have previously reported evidence of space-time clustering, suggesting that a transient environmental agent may be involved in etiology. To further examine whether a seasonally varying environmental agent may contribute to the etiology of PBC, we have analyzed seasonal variation with respect to month of diagnosis using population-based data from northeast England over a defined period (1987-2003). Date of diagnosis was defined as the earliest date at which the patient was found to have fulfilled any two of three diagnostic criteria (i.e., antimitochondrial antibody-positive titer ≥1 in 40, cholestatic liver blood tests, diagnostic or compatible liver histology). Monthly expected (E) numbers of cases were calculated under an assumption of a uniform distribution throughout the year. Observed counts (O) were compared with the expected numbers. The chi-squared heterogeneity test was used to test for overall nonuniform variation and also for individual months. Poisson regression analysis was used to fit a sinusoidal (i.e., harmonic) model to the data, using month of diagnosis as a covariate in the model. There was a marked peak for diagnoses in the month of June (O = 115, E = 84.7, O/E = 1.36; P = 0.001). Furthermore, there was evidence of a sinusoidal pattern with a June peak (P = 0.012).

CONCLUSION

These highly novel results provide further evidence for the involvement of a seasonally varying environmental agent in the etiology of PBC.

Primary sclerosing cholangitis

Primary sclerosing cholangitis (PSC) is a chronic liver condition which may affect both intra and extrahepatic biliary tree. Etiology of PSC remains to be fully elucidated but genetic, autoimmune, inflammatory and possibly infective factors could all contribute to its development. More than two-thirds of patients are males and the most commonly associated condition is an inflammatory bowel disease which occurs in up to 70% of affected subjects. Endoscopic cholangiopancreatography (ERCP) and magnetic resonanse cholangiopancreatography (MRCP) remain a gold standard in the diagnosis of this condition. No curative treatment of PSC exists and a proportion of patients who develop liver failure or suffer from recurrent episodes of cholangitis requires liver transplantation. PSC is associated with increased risk of malignancies, in particular cholangiocarcinoma which may arise in 12% of patients. The main aim of this chapter is to review the current knowledge on pathogenesis and clinical aspects of PSC as well as its associated malignancies.

An increased risk of urinary tract infection precedes development of primary biliary cirrhosis

Background

Primary Biliary Cirrhosis is known to be associated with Urinary Tract Infections (UTIs), but whether these precede or follow the liver disease is unclear. We have therefore attempted to determine whether UTIs are more common in people with Primary Biliary Cirrhosis (PBC) prior to their diagnosis.

Methods

We conducted a case control study in the General Practice Research Database. All cases of PBC first recorded at least one year after entry to the dataset were selected along with up to 10 controls matched for age, sex. A second unmatched control group who had Chronic Liver Diseases but not PBC were chosen. The main exposures studied were the occurrence of Urinary tract infections and pyelonephritis at least one or at least five years before diagnosis. We also performed an analysis restricted to those younger than 55 at diagnosis, as we hypothesized the relationship to be stronger in the younger age group.

Results

PBC is associated with UTI prior to diagnosis, OR 1.50 (CI 1.26-1.78), which was similar 5 years prior to diagnosis and after adjusting for smoking. The strongest relationships were observed in pyelonephritis exposures five years before diagnosis in cases under 55 years: adjusted odds ratios were 2.60 (1.02-6.63) in comparison with matched general population controls and adjusted odds ratios were OR 2.45 (1.02-5.59) in the comparison with chronic liver disease controls.

Conclusions

We found that the association between urosepsis and PBC is specific to this disease and precedes the diagnosis of PBC in a manner not previously observed in human data. This is consistent with a causal relationship.

Role of the anion exchanger 2 in the pathogenesis and treatment of primary biliary cirrhosis

The essential anion exchanger (AE) involved in biliary bicarbonate secretion is AE2/SLC4A2, a membrane protein which has also been recognized to be relevant for the regulation of the intracellular pH (pH(i)) in several cell types. Previously, we reported that the expression of AE2 mRNA is diminished in liver biopsies and peripheral blood mononuclear cells from patients with primary biliary cirrhosis (PBC). Immunohistochemical studies indicated that the expression of the AE2 protein is decreased in the bile ducts and hepatocytes in PBC livers. Moreover, we found that bile duct cells isolated from PBC patients and cultured for a few passages exhibit defective Na(+)-independent Cl(-)/HCO(3)(-) exchange. Interestingly, positron emission tomography studies have shown that PBC patients, even at early stages of the disease, fail to secrete bicarbonate to bile in response to secretin, a defect that can be partially reversed after several months of treatment with ursodeoxycholic acid. Altogether, these findings sustain our hypothesis that dysfunctions related to AE2 might have a role in the pathogenesis of PBC. Inadequate AE2 function in lymphocytes may disturb pH(i) regulation in these cells and alter immune homeostasis leading to autoimmunity. On the other hand, reduced AE2 in cholangiocytes could cause cholestasis and oxidative stress of bile duct cells. Cholangiocyte changes, together with altered immune homeostasis, could favor the development of antimitochondrial antibodies and the autoimmune attack on biliary ducts. Our recent findings that Ae2(a,b)-deficient mice indeed display most of these features strongly support the notion that AE2 abnormalities may be involved in the pathogenesis of PBC.

Primary biliary cirrhosis

Primary biliary cirrhosis is a chronic autoimmune inflammatory disease of the liver with a striking female preponderance. It has an insidious onset and typically affects middle-aged women. The disease manifests gradually with symptoms of fatigue, pruritis, and increased alkaline phosphatase levels on laboratory evaluation. The hallmark of the disease is the circulating antimitochondrial antibody. Histology is characterized by inflammation of the bile ducts, destruction of cholangiocytes, and subsequent cholestasis, progressing to biliary cirrhosis. The standard treatment for primary biliary cirrhosis is ursodeoxycholic acid, which improves survival, but the disease can still lead to cirrhosis and liver failure over decades.

Identification of Cd101 as a susceptibility gene for Novosphingobium aromaticivorans-induced liver autoimmunity

Environmental and genetic factors define the susceptibility of an individual to autoimmune disease. Although common genetic pathways affect general immunological tolerance mechanisms in autoimmunity, the effects of such genes could vary under distinct immune challenges within different tissues. In this study, we demonstrate this by observing that autoimmune type 1 diabetes-protective haplotypes at the insulin-dependent diabetes susceptibility region 10 (Idd10) introgressed from chromosome 3 of C57BL/6 (B6) and A/J mice onto the NOD background increase the severity of autoimmune primary biliary cirrhosis induced by infection with Novosphingobium aromaticivorans, a ubiquitous alphaproteobacterium, when compared with mice having the NOD and NOD.CAST Idd10 type 1 diabetes-susceptible haplotypes. Substantially increased liver pathology in mice having the B6 and A/J Idd10 haplotypes correlates with reduced expression of CD101 on dendritic cells, macrophages, and granulocytes following infection, delayed clearance of N. aromaticivorans, and the promotion of overzealous IFN-γ- and IL-17-dominated T cell responses essential for the adoptive transfer of liver lesions. CD101-knockout mice generated on the B6 background also exhibit substantially more severe N. aromaticivorans-induced liver disease correlating with increased IFN-γ and IL-17 responses compared with wild-type mice. These data strongly support the hypothesis that allelic variation of the Cd101 gene, located in the Idd10 region, alters the severity of liver autoimmunity induced by N. aromaticivorans.

Primary biliary cirrhosis

Primary biliary cirrhosis is a chronic liver disease characterised by intrahepatic bile-duct destruction, cholestasis, and, in some cases, cirrhosis. Evidence supporting the autoimmune nature of this disorder includes the appearance of highly specific antimitochondrial antibodies (AMAs) and autoreactive T cells. Concordance rates in monozygotic twins, familial prevalence, and genetic associations underscore the importance of genetic factors, whereas findings of epidemiological studies and murine models suggest a possible role for exogenous chemicals and infectious agents through molecular mimicry. The incidence of primary biliary cirrhosis has increased over recent decades, possibly attributable to augmented testing of liver biochemistry rather than a rise in disease incidence. AMAs remain the hallmark of diagnosis in most cases and allow detection of asymptomatic patients. Symptomatic individuals usually present with either pruritus or fatigue and, more rarely, with either jaundice or complications of cirrhosis. The prognosis of primary biliary cirrhosis has improved because of early diagnosis and use of ursodeoxycholic acid, the only established medical treatment for this disorder. Although not a cure, treatment can slow disease progression and delay the need for liver transplantation. However, some patients do not respond adequately to ursodeoxycholic acid and might need alternative therapeutic approaches.

Primary biliary cirrhosis: family stories

Primary biliary cirrhosis (PBC) is a chronic immune-mediated cholestatic liver disease of unknown aetiology which affects mostly women in middle age. Familial PBC is when PBC affects more than one member of the same family, and data suggest that first-degree relatives of PBC patients have an increased risk of developing the disease. Most often, these familial clusters involve mother-daughter pairs, which is consistent with the female preponderance of the disease. These clusters provide evidence towards a genetic basis underlying PBC. However, clusters of nonrelated individuals have also been reported, giving strength to an environmental component. Twin studies have demonstrated a high concordance for PBC in monozygotic twins and a low concordance among dizygotic twins. In conclusion, studies of PBC in families clearly demonstrate that genetic, epigenetic, and environmental factors play a role in the development of the disease.

Disease-specific autoantibodies in primary biliary cirrhosis

Anti-mitochondrial autoantibodies (AMA) are specific markers of primary biliary liver cirrhosis (PBC), a cholestatic autoimmune disease which is characterised by a progressive destruction of the biliary epithelial cells followed by fibrosis, cirrhosis and liver failure. The prevalence of AMA in PBC is more than 90% and they can precede long before the clinical symptoms. AMA are conventionally detected by indirect immunofluorescence (IIF) using rodent liver, kidney, and stomach sections as substrates. Additionally, different PBC-specific anti-nuclear autoantibodies (ANA) can be observed in 30% of patients presenting with multiple nuclear dot or nuclear membrane staining patterns, which preferentially are identified using HEp-2 cells as substrate. The identification of the major PBC-specific mitochondrial and nuclear targets has allowed the generation of monospecific antigenic targets which are increasingly used in solid-phase assays for routine detection of AMA and ANA in mono- or multiparametric screen test systems. In the present paper, we give an overview of the diagnostic significance of autoantibodies in PBC, discuss the competencies of different techniques used for their determination and propose an effective diagnostic strategy.

Innate immunity and primary biliary cirrhosis: activated invariant natural killer T cells exacerbate murine autoimmune cholangitis and fibrosis

Murine models of autoimmunity allow the study of the earliest events in disease pathogenesis. Our laboratory has developed a xenobiotic induced model of primary biliary cirrhosis (PBC) following immunization of mice with 2-octynoic acid coupled to bovine serum albumin (2-OA-BSA), an antigen selected following quantitative structure-activity relationship analysis of the E2 subunit of the pyruvate dehydrogenase complex (PDC-E2), the immunodominant autoantigen of PBC. Recent data in humans with PBC has suggested that a major component of liver pathology is due to activation of innate immunity. We took advantage of our 2-OA-BSA model and immunized mice with and without the addition of α-galactosylceramide (α-GalCer), an invariant natural killer T cell activator. Importantly, we report herein that 2-OA-BSA-immunized mice exposed to α-GalCer develop a profound exacerbation of their autoimmune cholangitis, including significant increases in CD8(+) T-cell infiltrates, portal inflammation, granuloma formation, and bile duct damage. Furthermore, such mice produce increased levels of antimitochondrial antibodies and have evidence of fibrosis, a feature not previously reported in the murine models of PBC.

CONCLUSION

Our data suggests a primary role of innate immunity in the exacerbation of autoimmune cholangitis and also become a logical explanation for the recurrence of PBC following liver transplantation in the absence of major histocompatability complex compatibility. We submit that PBC begins with loss of tolerance to PDC-E2 and a multilineage antimitochondrial response in which autoreactive CD8(+) T cells are critical. However, the perpetuation of disease and its exacerbation will also be modulated by innate immune mechanisms.

Genetic susceptibility to autoimmune liver disease

Autoimmune hepatitis (AIH), primary sclerosing cholangitis (PSC) and primary biliary cirrhosis (PBC) are considered as putative autoimmune diseases of the liver. Whereas strong evidence that bacterial infection may trigger PBC exists, the etiologies for PSC and AIH remain unknown. Although there have been significant discoveries of genetic polymorphisms that may underlie the susceptibility to these liver diseases, their associations with environmental triggers and the subsequent implications have been difficult to elucidate. While single nucleotide polymorphisms within the negative costimulatory molecule cytotoxic T lymphocyte antigen 4 (CTLA-4) have been suggested as genetic susceptibility factors for all three disorders, we discuss the implications of CTLA-4 susceptibility alleles mainly in the context of PBC, where Novosphingobium aromaticivorans, an ubiquitous alphaproteobacterium, has recently been specifically associated with the pathogenesis of this devastating liver disease. Ultimately, the discovery of infectious triggers of PBC may expand the concept of genetic susceptibility in immune-mediated liver diseases from the concept of aberrant immune responses against self-antigens to insufficient and/or inappropriate immunological defense mechanisms allowing microbes to cross natural barriers, establish infection and damage respective target organs.

Biliary epithelial apoptosis, autophagy, and senescence in primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is a chronic cholestatic liver disease characterized serologically by the high prevalence of anti-mitochondrial autoantibodies (AMAs) and histologically by the cholangitis of small bile ducts, eventually followed by extensive loss of the small bile duct. An autoimmune pathogenesis is suggested by clinical and experimental studies, but there remain issues regarding the etiology, the significance of AMAs in the pathogenesis of bile duct lesions, and so on. The unique properties of apoptosis in biliary epithelial cells (BECs), in which there is exposure of autoantigen to the effectors of the immune system, are proposed to be a cause of bile duct lesions in PBC. Recent progress disclosed that cellular senescence and autophagy are involved in bile duct lesions in PBC. Senescent BECs may modulate the periductal microenvironment by expressing senescence-associated secretory phenotypes, including various chemokines, and contribute to the pathogenesis of bile duct lesions in PBC.

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.

Immune-mediated bile duct injury: The case of primary biliary cirrhosis

Autoimmune cholangitis would be the appropriate name to define the immune-mediated bile duct injury following the breakdown of tolerance to mitochondrial proteins and the appearance of serum autoantibodies and autoreactive T cells. Nevertheless, the condition is universally named primary biliary cirrhosis (PBC). The disease etiology and pathogenesis remain largely unknown despite the proposed lines of evidence. One twin study and numerous epidemiology reports suggest that both a susceptible genetic background and environmental factors determine disease onset while a recent genome-wide association study proposed highly significant associations with several common genetic polymorphisms in subgroups of patients. Specific infectious agents and chemicals may contribute to the disease onset and perpetuation in a genetically susceptible host, possibly through molecular mimicry. Importantly, several murine models have been proposed and include strains in which PBC is genetically determined or induced by immunization with chemicals and bacteria. From a pathogenetic standpoint, new exciting data have demonstrated the unique apoptotic features of bile duct cells that allow the mitochondrial autoantigens to be taken up in their intact form within apoptotic blebs. We are convinced that the application of the most recent molecular techniques will soon provide developments in PBC etiology and pathogenesis with likely implications in diagnostics and therapeutics.

Demographic, lifestyle, medical and familial factors associated with primary biliary cirrhosis

BACKGROUND & AIMS

Primary biliary cirrhosis (PBC) is believed to result from the interaction of genetic and environmental factors. The controlled studies aiming to assess risk factors for PBC are still limited. Our aim was to identify risk factors and co-morbidities associated with PBC in a large monocentric cohort.

METHODS

We enrolled 222 patients with PBC and 509 controls matched for age, gender, and residential location. Standardized questionnaire data, including more than 200 questions regarding demographic and anthropometric features, lifestyle, individual and familial medical history, and reproductive history, were prospectively collected and examined. Risk factors with odds ratio (OR) and confidence intervals (CI) were determined using conditional logistic regression analyses.

RESULTS

Family history of PBC (OR 6.8, 95% CI 2.8-16.4) or autoimmune thyroid disease (AITD) (OR 7.1, 95% CI 3.5-14.5) in first-degree relatives, and individual history of active or passive smoking (OR 3.1, 95% CI 2.0-5.0), recurrent urinary tract infections (UTI) (OR 2.7; 95% CI 2.0-3.7), AITD (OR 7.7, 95% CI 4.8-12.3), Sjögren syndrome (OR 11.9, 95% CI 5.4-26.3), Raynaud syndrome (OR 7.2, 95% CI 4.3-12.1), pruritus during pregnancy (OR 3.9, 95% CI 2.8-5.3), or abortion (OR 2.0, 95% CI 1.6-2.5) were significantly associated with increased risk of PBC, while use of oral contraceptives (OR 0.6; 95% CI 0.5-0.8) was associated with decreased risk.

CONCLUSION

This study confirms some of the previously reported risk factors for PBC, namely family history of disease and individual history of smoking, UTI, and autoimmune conditions, and further identifies the use of oral contraceptives as a putative protective factor.

Linking human beta retrovirus infection with primary biliary cirrhosis

Several environmental agents have been linked with primary biliary cirrhosis (PBC) that include bacteria, xenobiotics and viruses. A human beta retrovirus (HBRV) related to mouse mammary tumor virus has been cloned and characterized from patients with PBC. This agent can be detected in the majority of patients' perihepatic lymph nodes by immunochemistry and RT-PCR. The HBRV has recently been isolated in culture and integration sites have been identified in the genome of patients to provide convincing evidence of beta retrovirus infection in patients. Three lines of evidence support a role for the virus in PBC. First, the beta retrovirus is linked with aberrant expression of mitochondrial protein(s) on the biliary epithelium cell (BEC) surface, a disease specific phenotype. Second, the related agent, mouse mammary tumor virus has been linked with autoimmune biliary disease in the NOD.c3c4 mouse model for PBC. In this mouse model, the virus is localized to diseased biliary epithelium that also display aberrant expression of the mitochondrial autoantigens. In translational studies, both patients with PBC and NOD.c3c4 mice demonstrate significant improvement in biliary disease with combination antiviral therapy. An overview of the biological relevance of the beta retrovirus infection in PBC will be discussed in this review.

Environmental factors and the induction of autoimmunity in primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is a chronic cholestatic disease with an autoimmune pathogenesis and an unknown etiology, predominantly affecting postmenopausal women. The term PBC is a misnomer since most cases currently diagnosed have limited probability to develop cirrhosis. Antimitochondrial autoantibodies, elevated IgM and selective destruction of the intrahepatic bile ducts are the hallmarks of PBC. A permissive genetic background is critical in producing susceptibility despite limited associations with alleles within the MHC. The disease has incomplete concordance in monozygotic twins and its geoepidemiology suggests a role for environmental factors in the induction of PBC. This hypothesis is further supported by clinical (risk factors) and experimental evidence. Some of the factors incriminated model molecular mimicry by infectious agents and xenobiotic chemicals. Additional candidates are being proposed through large screening; all proposed associations ultimately require confirmation in animal models and clinical practice.

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.

Cytochrome P450 2D6 as a model antigen

Cytochrome P450 2D6 (CYP2D6) has been identified as the major autoantigen in type 2 autoimmune hepatitis (AIH). However, because of a lack of appropriate animal models, the etiology of AIH is still poorly understood. We generated a mouse model for AIH using the human CYP2D6 as a triggering molecule for autoimmunity. We infected wild-type FVB mice with an adenovirus expressing human CYP2D6 (Ad-2D6) to break self-tolerance to the mouse CYP2D6 homologues. Ad-2D6-infected mice showed persistent features of liver damage including hepatic fibrosis, cellular infiltrations, focal-to-confluent necrosis and generation of anti-CYP2D6 antibodies, which predominantly recognized the identical immunodominant epitope recognized by LKM-1 antibodies from AIH patients. Interestingly, Ad-2D6 infection of transgenic mice expressing the human CYP2D6 (CYP2D6 mice) resulted in delayed kinetics and reduced severity of liver damage. However, the quantity and quality of anti-CYP2D6 antibodies was only moderately reduced in CYP2D6 mice. In contrast, the frequency of CYP2D6-specific CD4 and CD8 T cells was dramatically decreased in CYP2D6 mice, indicating the presence of a strong T cell tolerance to human CYP2D6 established in CYP2D6 mice, but not in wild-type mice. CYP2D6-specific T cells reacted to human CYP2D6 peptides with intermediate homology to the mouse homologues, but not to those with high homology, indicating that molecular mimicry rather than molecular identity breaks tolerance and subsequently causes severe persistent autoimmune liver damage. The CYP2D6 model provides a platform to investigate mechanisms involved in the immunopathogenesis of autoimmune-mediated chronic hepatic injury and evaluate possible ways of therapeutic interference.

Primary biliary cirrhosis: a 2010 update

Primary biliary cirrhosis (PBC) is a chronic inflammatory autoimmune disease that mainly targets the cholangiocytes of the interlobular bile ducts in the liver. The condition primarily affects middle-aged women. Without treatment, PBC generally progresses to cirrhosis and eventually liver failure over a period of 10-20 years. PBC is a rare disease with prevalence of less than 1/2000. PBC is thought to result from a combination of multiple genetic factors and superimposed environmental triggers. The contribution of the genetic predisposition is evidenced by the familial clustering. Several risk factors, including exposure to infectious agents and chemical xenobiotics, have been suggested. Ursodeoxycholic acid (UDCA) is currently the only FDA-approved medical treatment for PBC. When administered at doses of 13-15 mg/kg/day, a majority of patients with PBC have a normal life expectancy without additional therapeutic measures. One out of three patients does not adequately respond to UDCA therapy and may need additional medical therapy and/or liver transplantation. This review summarises current knowledge on the epidemiology, ethiopathogenesis, clinical, and therapeutic aspects of PBC.

Murine models of autoimmune cholangitis

PURPOSE OF REVIEW

Primary biliary cirrhosis (PBC) is a human autoimmune liver disease whose molecular pathogenesis is poorly understood because of the difficulty in accessing human tissue and the absence of appropriate animal models. Recently, several unique murine models of human PBC have been discovered. These models have great potential for illustrating the cause and the cellular events that lead to biliary-specific damage. The purpose of this review is to summarize recent progress in these models.

RECENT FINDINGS

The murine models of autoimmune cholangitis include the transforming growth factor beta receptor II (TGF-betaRII) dominant-negative (dnTGF-betaRII), IL-2 receptor alpha deleted (IL-2Ralpha-/-), scurfy, nonobese diabetic (NOD) c3c4, and Ae2 gene-disrupted (Ae2a,b-/-) mice. Recently, we have also established a successful murine model following the immunization with a chemical mimicry of the lipoyl-lysine residue of the E2 component of PDC-E2.

SUMMARY

These emerging murine models have greatly enabled researchers to address the pathogenesis of human PBC and to elucidate pathogenic factors. These models will ultimately lead to new therapeutic options for human PBC.

Long-term bacterial exposure can trigger nonsuppurative destructive cholangitis associated with multifocal epithelial inflammation

Bacterial infection has become a focus of attention in the pathogenesis of primary biliary cirrhosis (PBC). We earlier reported that the bacterial lipoteichoic acid was detected at the sites of inflammation around damaged bile ducts in the livers of PBC, and PBC patients' sera showed high titers against streptococcal histone-like protein. Here, we investigated whether chronic bacterial exposure could trigger PBC-like epithelial cell damage in normal mouse. BALB/c mice were repeatedly inoculated with various bacteria for 8 weeks. At 1 week (Group 1) and 3, 4, or 20 months (long term; Group 2) after the final inoculation, mice were killed to obtain samples. In the livers of the Streptococcus intermedius (S.i.)-inoculated mice in Group 1, cellular infiltration was predominantly observed around the bile ducts over the hepatic parenchyma. In the S.i.-inoculated mice in Group 2, portal but not parenchymal inflammation was observed in the livers, and periductal cellular infiltrates were detected in the salivary glands. Both S.i.-inoculated Groups 1 and 2 BALB/c mice sera had antibodies against HuCCT1 biliary epithelial cells, anti-nuclear antibodies, and anti-gp210 antibodies, but not anti-mitochondrial antibodies. Immunoreactivity to histone-like DNA-binding protein of S.i. (S.i.-HLP) was detectable around the sites of chronic nonsuppurative destructive cholangitis in the portal area in the livers of both S.i.-inoculated Groups 1 and 2 BALB/c mice. Furthermore, anti-S.i.-HLP antibody bound to synthetic gp210 peptide, as well. Bacteria triggered PBC-like cholangitis, multifocal epithelial inflammation, and autoantibody production. Bacteria are likely involved in the pathogenesis of PBC and of associated multifocal epithelial inflammation.

Natural killer T cells are not the predominant T cell in asthma and likely modulate, not cause, asthma

Asthma is a multifactorial disease of the airways characterized by airway inflammation, mucus hypersecretion, and airway hyperresponsiveness. Conventional MHC class II-restricted CD4(+) T cells are considered a key cell in asthma pathogenesis because they have a broad T-cell receptor repertoire, providing specificity and reactivity to diverse protein allergens. This notion was challenged when a study found that invariant Natural Killer (NK) T cells were the predominant T cells in the lung and bronchoalveolar lavage fluid of all asthmatic subjects studied. This finding was provocative because invariant NKT cells have a very limited T-cell receptor repertoire and are specific for a restricted set of lipid antigens that bind to CD1d, a nonpolymorphic MHC-like molecule. However, multiple subsequent studies failed to replicate the initial study and instead found that invariant NKT cells are present as a small fraction of the total T cells in the asthmatic lung. Thus, we believe that although CD1d-restricted NKT cells might play a role in modulating the asthmatic phenotype, they are not the critical drivers of the asthmatic response, a role we believe is still held by conventional MHC class II-restricted CD4(+) T cells.

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.

Are transient environmental agents involved in the cause of primary biliary cirrhosis? Evidence from space-time clustering analysis

The cause of primary biliary cirrhosis (PBC) is unclear. Both genetic and environmental factors are likely to contribute. Some studies have suggested that one or more infectious agents may be involved. To examine whether infections may contribute to the cause of PBC, we have analyzed for space-time clustering using population-based data from northeast England over a defined period (1987-2003). Space-time clustering is observed when excess cases of a disease are found within limited geographical areas at limited periods of time. If present, it is suggestive of the involvement of one or more environmental components in the cause of a disease and is especially supportive of infections. A second-order procedure based on K-functions was used to test for global space-time clustering using residential addresses at the time of diagnosis. The Knox method determined the spatiotemporal range over which global clustering was strongest. K-function tests were repeated using nearest neighbor thresholds to adjust for variations in population density. Individual space-time clusters were identified using Kulldorff's scan statistic. Analysis of 1015 cases showed highly statistically significant space-time clustering (P < 0.001). Clustering was most marked for cases diagnosed within 1-4 months of one another. A number of specific space-time clusters were identified. In conclusion, these novel results suggest that transient environmental agents may play a role in the cause of PBC.

Viral triggers for autoimmunity: is the 'glass of molecular mimicry' half full or half empty?

In this review we want to consider some of the requirements for autoimmune disease to develop and how this may be reproduced in animal models. Besides a genetic predisposition, environmental triggering factors seem to play a central role in the etiology of many autoimmune diseases. In theory, a structural similarity or identity between the host and an invading pathogen might cause the immune system of the host to react not only to the pathogen but also to self-components. However, in order for such a process of molecular mimicry to induce autoimmunity the mechanisms of maintaining tolerance or ignorance to the self-components need to be circumvented. Subsequently, in order to advance autoimmunity to overt autoimmune disease the frequency and avidity of autoaggressive lymphocytes has to be of sufficient magnitude. Intuitively, one would assume that tolerance might be stronger to identical structures than to structures that just share a certain degree of similarity. Self-reactive lymphocytes with high-avidity are more likely to be deleted or functionally silenced by central and/or peripheral tolerance mechanisms. Thus, perfect mimicry between identical structures might fail in inducing autoimmunity because of efficient tolerance mechanisms. In contrast, imperfect mimicry between similar but not identical structures might on one hand circumvent tolerance but on the other hand result in the generation of lymphocytes with only low- to intermediate avidity. Here we examine animal models that use the concept of molecular mimicry as a potential mechanism for inducing or accelerating autoimmunity. We focus on the RIP-LCMV model for type 1 diabetes and the novel cytochrome P450 2D6 (CYP2D6) model for autoimmune hepatitis, which use either identical or similar triggering and target antigens.

Innate-like recognition of microbes by invariant natural killer T cells

Invariant natural killer T cells (iNKT cells) express a restricted T cell antigen receptor (TCR) repertoire and they respond rapidly to glycolipid antigens presented by CD1d. These glycolipid antigens have hexose sugars in alpha-linkage to two types of lipids that can bind to CD1d. Recent work has shown that the responses of iNKT cells to antigen-bearing microbes can have a profound impact on the development of inflammatory diseases. iNKT cells overcome the limitation of their limited TCR diversity by also responding in a foreign antigen-independent fashion to some infectious agents, similar to NK cells. Recent results demonstrate several mechanisms for the indirect activation of iNKT cells by viruses or TLR ligands, dependent on self-antigen recognition and/or different cytokines produced by antigen presenting cells. The means by which iNKT cells influence other cell types and overall host defense are likewise diverse, illustrating the flexibility and functional diversity of this T lymphocyte sublineage.

The role of environmental factors in primary biliary cirrhosis

The etiology of primary biliary cirrhosis (PBC) is enigmatic, although it is clearly related to a combination of genetic predisposition and environmental stimulation. PBC is a chronic autoimmune cholestatic liver disease that occurs throughout the world with a reported latitudinal gradient in prevalence and incidence. PBC is also characterized by a 60% concordance in monozygotic twins and is considered a model autoimmune disease because of several features common to other conditions and the relatively homogeneous serological and biochemical features. Several risk factors have been suggested to be associated with PBC, including exposure to infectious agents and chemical xenobiotics. This review will attempt to place such factors in perspective.

Primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is an immune-mediated chronic cholestatic liver disease with a slowly progressive course. Without treatment, most patients eventually develop fibrosis and cirrhosis of the liver and may need liver transplantation in the late stage of disease. PBC primarily affects women (female preponderance 9–10:1) with a prevalence of up to 1 in 1,000 women over 40 years of age. Common symptoms of the disease are fatigue and pruritus, but most patients are asymptomatic at first presentation. The diagnosis is based on sustained elevation of serum markers of cholestasis, i.e., alkaline phosphatase and gamma-glutamyl transferase, and the presence of serum antimitochondrial antibodies directed against the E2 subunit of the pyruvate dehydrogenase complex. Histologically, PBC is characterized by florid bile duct lesions with damage to biliary epithelial cells, an often dense portal inflammatory infiltrate and progressive loss of small intrahepatic bile ducts. Although the insight into pathogenetic aspects of PBC has grown enormously during the recent decade and numerous genetic, environmental, and infectious factors have been disclosed which may contribute to the development of PBC, the precise pathogenesis remains enigmatic. Ursodeoxycholic acid (UDCA) is currently the only FDA-approved medical treatment for PBC. When administered at adequate doses of 13–15 mg/kg/day, up to two out of three patients with PBC may have a normal life expectancy without additional therapeutic measures. The mode of action of UDCA is still under discussion, but stimulation of impaired hepatocellular and cholangiocellular secretion, detoxification of bile, and antiapoptotic effects may represent key mechanisms. One out of three patients does not adequately respond to UDCA therapy and may need additional medical therapy and/or liver transplantation. This review summarizes current knowledge on the clinical, diagnostic, pathogenetic, and therapeutic aspects of PBC.

Mycoplasma antigens as a possible trigger for the induction of antimitochondrial antibodies in primary biliary cirrhosis

BACKGROUND

In primary biliary cirrhosis (PBC), autoreactivity mainly targets members of the pyruvate dehydrogenase complex (PDC). Because PDC subunits are expressed on the surface of mycoplasma and molecular mimicry may be one aetiological factor, we analysed the presence of mammalian and mycoplasma PDC-specific antibodies in PBC patients.

METHODS

Antibodies to porcine PDC and Mycoplasma pneumoniae (mp) antigens mpPDH-C (to be designated mpPDC-E2 chain), mpPDH-B (to be designated mpPDC-E1beta chain), mpCARDS TX and mpP1 were investigated in sera from 43 PBC patients, 19 patients with autoimmune hepatitis and 11 healthy controls by an enzyme-linked immunosorbent assay and Western blotting. To study the rate of acute mycoplasma infection, an adhesin P1-specific polymerase chain reaction (PCR) was performed.

RESULTS

Immune reactivity to the mpPDC-E2 antigen was significantly enhanced in PBC patients (83.7%) as compared with controls (overall frequency of 36.7%), while antibodies to the porcine PDC-E2 chain were found only in PBC patients (88%) excluding a simple cross-reactivity of PDC-related antibodies. This observation was confirmed by inhibition studies demonstrating that porcine PDC did not inhibit mycoplasma PDC-specific antibodies and vice versa. The occurrence of antibodies to mpPDC seems to precede the occurrence of antibodies to porcine PDC. Infection with mycoplasma was equally distributed in the groups as evidenced by an antibody frequency comparable to CARDS TX and P1 and PCR reactivity.

CONCLUSION

Because PBC patients show a significantly enhanced frequency of mpPDC-E2-related antibodies, besides other factors, molecular mimicry between surface molecules of mycoplasma and epitopes of the autoantigen may play a central role in the aetiopathology of PBC.

Common genetic variation and haplotypes of the anion exchanger SLC4A2 in primary biliary cirrhosis

OBJECTIVES

Deficiencies of the anion exchanger SLC4A2 are thought to play a pathogenic role in primary biliary cirrhosis (PBC), as the evidenced by decreased expression and activity in PBC patients and development of disease features in SLC4A2 knockout mice. We hypothesized that genetic variation in SLC4A2 might influence this pathogenic contribution. Thus, we aimed to perform a comprehensive assessment of SLC4A2 genetic variation in PBC using a linkage disequilibrium (LD)-based haplotype-tagging approach.

METHODS

Twelve single nucleotide polymorphisms (SNPs) across SLC4A2 were genotyped in 409 PBC patients and 300 controls and evaluated for association with disease, as well as with prior orthotopic liver transplant and antimitochondrial antibody (AMA) status among the PBC patients, both individually and as inferred haplotypes, using logistic regression.

RESULTS

All SNPs were in Hardy-Weinberg equilibrium. No associations with disease or liver transplantation were detected, but two variants, rs2303929 and rs3793336, were associated with negativity for antimitochondrial antibodies among the PBC patients.

CONCLUSIONS

The common genetic variation of SLC4A2 does not directly affect the risk of PBC or its clinical outcome. Whether the deficiency of SLC4A2 expression and activity observed earlier in PBC patients is an acquired epiphenomenon of underlying disease or is because of heritable factors in unappreciated regulatory regions remains uncertain. Of note, two SLC4A2 variants appear to influence AMA status among PBC patients. The mechanisms behind this finding are unclear.

Ursodeoxycholic acid reduces CpG-induced IgM production in patients with primary biliary cirrhosis

AIM

Ursodeoxycholic acid (UDCA) treatment reduces IgM serum levels in patients with primary biliary cirrhosis (PBC) without affecting serum antimitochondrial antibody (AMA) titers. We previously reported that PBC-associated hyper-IgM is secondary to a disease-specific hyperproduction following bacterial stimulation by B cells.

METHODS

We isolated peripheral blood mononuclear cells (PBMC) from patients with PBC and controls and evaluated whether bacterial CpG challenge in the presence of UDCA at concentrations consistent with those achieved in treated patients led to changes in total IgM, IgG-AMA, and IgM-AMA production. Further, p65 phosphorylation and CD38 cell expression were analyzed as measures of activation of the NF-kB signaling pathway and B cell subsets, respectively.

RESULTS

UDCA significantly reduced CpG-induced total IgM and IgM-AMA production, but had no impact on IgG-AMA production. UDCA also significantly reduced the activation ofnaïve and IgM memory, but not IgG memory, B cells, as represented by CD38 expression levels. Further, p65 phosphorylation was significantly reduced in the presence of UDCA.

CONCLUSION

UDCA reduces total and IgM-AMA production in PBMC from patients with PBC by downregulating B cell activation and NF-kB signaling. These data ultimately suggest novel mechanisms of action for UDCA in chronic autoimmune cholestasis.

Bacteria and primary biliary cirrhosis

Infectious agents have been postulated to play a pathogenic role in the loss of immunological tolerance and the induction of primary biliary cirrhosis, an immune-mediated cholestatic liver disease characterized by progressive destruction of the small intrahepatic bile ducts and subsequent cirrhosis and liver failure. This review discusses emerging issues implicating infectious agents such as Escherichia coli, mycobacteria, chlamydia, helicobacter species, lactobacilli, Novosphingobium aromaticivorans, and betaretroviruses in the pathogenesis of primary biliary cirrhosis. We also review the immunopathological mechanisms responsible for the induction of the disease with special emphasis on the role of molecular mimicry and microbial/self immunological cross-reactivity.

Human leukocyte antigen polymorphisms in Italian primary biliary cirrhosis: a multicenter study of 664 patients and 1992 healthy controls

Genetic factors are critical in determining susceptibility to primary biliary cirrhosis (PBC), but there has not been a clear association with human leukocyte antigen (HLA) genes. We performed a multicenter case-control study and analyzed HLA class II DRB1 associations using a large cohort of 664 well-defined cases of PBC and 1992 controls of Italian ancestry. Importantly, healthy controls were rigorously matched not only by age and sex, but also for the geographical origin of the proband four grandparents (Northern, Central, and Southern Italy). After correction for multiple testing, DRB1*08 [odds ratio (OR), 3.3; 95% confidence interval (CI), 2.4-4.5] and DRB1*02 (OR 0.9; 95% CI 0.8-1.2) were significantly associated with PBC, whereas alleles DRB1*11 (OR 0.4; 95% CI 0.3-0.4) and DRB1*13 (OR 0.7; 95% CI 0.6-0.9) were protective. When subjects were stratified according to their grandparental geographical origin, only the associations with DRB1*08 and DRB1*11 were common to all three areas. Associated DRB1 alleles were found only in a minority of patients, whereas an additive genetic model is supported by the gene dosage effect for DRB1*11 allele and the interaction of DRB1*11,*13, and *08. Lastly, no significant associations were detected between specific DRB1 alleles and relevant clinical features represented by the presence of cirrhosis or serum autoantibodies. In conclusion, we confirm the role for HLA to determine PBC susceptibility and suggest that the effect of HLA is limited to patient subgroups. We suggest that a large whole-genome approach is required to identify further genetic elements contributing to the loss of tolerance in this disease.

Natural history and prognostic factors of primary biliary cirrhosis in Taiwan: a follow-up study up to 18 years

PURPOSE

The natural history of primary biliary cirrhosis (PBC) has been little studied in Asia. We conducted a Taiwanese cohort study on the natural history of PBC and analysed the prognostic factors.

METHODS

This study enrolled 96 consecutive PBC patients between 1985 and 2006 to evaluate the baseline characteristics and outcomes.

RESULTS

There were 74 females and 22 males. Eighty-five were positive for antimitochondrial antibodies in sera, and 11 were negative. The clinical manifestations and prognosis were similar between these two groups. In a median follow-up of 47.5+/-55.8 months, 27 patients died. Multivariate analysis indicated that the independent prognostic factors were serum albumin (P=0.021), creatinine (P=0.033) and ursodeoxycholic acid treatment (P=0.008). Besides, 42 patients developed adverse outcomes. Albumin (P<0.001), bilirubin (P=0.019) and prothrombin time (PT) (P=0.010) were significant factors. Moreover, a Mayo risk score <5, a Model for End-Stage Liver Disease (MELD) score <6, a Child-Pugh stage A and early liver histology were associated with favourable outcomes.

CONCLUSION

Serum albumin, bilirubin and PT were independent prognostic factors of adverse outcomes for Taiwanese PBC patients. Besides, the Mayo risk score, the MELD score, the Child-Pugh stage and liver histology were also validated to predict survival.