The causes of primary biliary cirrhosis: Convenient and inconvenient truths

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.

Interaction between Toll-like receptors and natural killer cells in the destruction of bile ducts in primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is characterized by chronic nonsuppurative destructive cholangitis (CNSDC) associated with destruction of small bile ducts. Although there have been significant advances in the dissection of the adaptive immune response against the mitochondrial autoantigens, there are increasing data that suggest a contribution of innate immune mechanisms in inducing chronic biliary pathology. We have taken advantage of our ability to isolate subpopulations of liver mononuclear cells (LMC) and examined herein the role of Toll-like receptors (TLRs), their ligands, and natural killer (NK) cells in modulating cytotoxic activity against biliary epithelial cells (BECs). In particular, we demonstrate that Toll-like receptor 4 ligand (TLR4-L)-stimulated NK cells destroy autologous BECs in the presence of interferon alpha (IFN-α) synthesized by TLR 3 ligand (TLR3-L)-stimulated monocytes (Mo). Indeed, IFN-α production by hepatic Mo is significantly increased in patients with PBC compared to disease controls. There were also marked increases in the cytotoxic activity of hepatic NK cells from PBC patients compared to NK cells from controls but only when the NK cells were prepared following ligation of both TLR3-L- and TLR4-L-stimulated LMC. These functional data are supported by the immunohistochemical observation of an increased presence of CD56-positive NK cells scattered around destroyed small bile ducts more frequently in liver tissues from PBC patients than controls.

CONCLUSION

These data highlight critical differences in the varied roles of Mo and NK cells following TLR3-L and TLR4-L stimulation.

Smoking and severity of hepatic fibrosis in nonalcoholic fatty liver disease

BACKGROUND & AIMS

Although many predictors of disease severity of nonalcoholic fatty liver disease (NAFLD) have been proposed, studies of the potential effects of specific environmental exposures on human NAFLD are lacking. Smoking increases insulin resistance. Given the pathophysiological role of insulin resistance in NAFLD, characterization of the influence of smoking in NAFLD is warranted. The aim of this paper was to study the potential association between cigarette smoking and advanced fibrosis in NAFLD.

METHODS

All adults enrolled in the NASH CRN studies, between October 2004 and February 2008, who had liver biopsies, were included (n=1091). Advanced fibrosis was defined as stages 3-4. Analyses were performed.

RESULTS

Significant bivariate associations were demonstrated between advanced fibrosis and age, gender, ethnicity, diabetes, and smoking history. History of smoking ≥ 10 pack-years was more common (p <0.0001) among patients with advanced fibrosis. Multivariate analysis demonstrated an association between smoking history of ≥ 10 pack-years and advanced fibrosis (OR=1.63). Among non-diabetics, history of ≥ 10 pack-years was associated with an OR of 2.48 for advanced fibrosis. High frequencies of advanced fibrosis were observed among diabetics (with or without ≥ 10 pack-years history) and non-diabetics with ≥ 10 pack-years history as compared to non-diabetics without significant smoking history.

CONCLUSIONS

Smoking history was associated with advanced liver fibrosis in this large multicenter cohort of NAFLD patients. The results indicate that smoking may enhance the progression of NAFLD partly through its effect on insulin resistance. Our results are consistent with recent animal studies suggesting that cigarette smoke may aggravate fatty liver. To our knowledge, this is the first study to show that cigarette smoking is associated with increased fibrosis severity in human NALFD, suggesting it may accelerate disease progression. These results may support a formal recommendation of smoking cessation in patients with NAFLD.

Fetomaternal alloimmunity as a cause of liver disease

Fetomaternal alloimmune disease has traditionally been associated with haematological disease such as fetomaternal alloimmune thrombocytopaenia and Rh haemolytic anaemia, but is now known to also be organ specific. Alloimmune membranous glomerulonephritis (AMG) is one of the most well understood organ-specific alloimmune diseases. Neonatal haemochromatosis (NH) is a rare condition characterised by early liver failure in infants, with evidence suggesting that it is also alloimmune. Both AMG and NH appear to involve the passive transfer of alloantibodies to the fetus, which bind a specific alloantigen, fix complement and activate the terminal complement cascade. Although differences between AMG and NH are known, and evidence of the presence of antigen-specific alloantibodies in NH is still missing, we will use AMG as an example of fetomaternal organ specific alloimmune disease, and critically compare this to other emerging evidence that indicates that NH is also alloimmune.

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.

The impact of biopsychosocial factors on quality of life: women with primary biliary cirrhosis on waiting list and post liver transplantation

OBJECTIVES

Primary biliary cirrhosis (PBC) is the second most common reason for liver transplants among women in the USA. While survival rates are high, there is evidence of persistent problems post-transplant. This study aimed to identify significant contributors to quality of life (QOL) for women with PBC on waiting list (WL) and post-transplant (PT) and compare QOL in each group with US population norms.

DESIGN

A cross-sectional, two-group study design was used.

METHODS

WL and PT participants were recruited through medical centres and on-line. QOL was measured by the Short Form-36 and an indicator of Social QOL created for this study. A biopsychosocial model incorporating demographic, biomedical, psychological, and sociological factors guided choice of variables affecting QOL. Analyses examined (1) all factors for differences between WL and PT groups, (2) association between factors and QOL outcomes within each group, (3) multivariate regression of QOL on factors in the model for the sample as a whole, and (4) comparison of QOL outcomes with national norms.

RESULTS

One hundred women with PBC participated in the study, 25 on WL and 75 PT. Group comparisons showed improvement for PT participants in most biomedical and psychological variables and in QOL outcomes. QOL was related to many, but not all, of the variables in the model. In multivariate analysis, Fatigue, Depression, Coping, and Education - but not Transplant Status - were identified as indicators of QOL. Physical QOL improved significantly after 5 years PT, when it was no longer worse than national norms. Mental QOL remained worse than national norms despite distance in time from transplant.

CONCLUSIONS

The model proved useful in identifying a range of factors that contributed to QOL for women with PBC before and after transplant. Recommendations were made for clinical practice to improve QOL through a combination of treatment and self-management.

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.

Chronic fibrosing cholangiopathies: a consequence of a defective HCO₃⁻ "umbrella"?

The pathogenesis of chronic cholangiopathies, in particular primary biliary cirrhosis and primary sclerosing cholangitis, is still obscure. A stimulating hypothesis is proposed by Beuers et al. They reason that, since cholangiocytes are exposed to high concentrations of hydrophobic bile salts that are toxic at μM concentrations, these cells had to develop protective mechanisms. Apart from micelle formation, the authors argue that biliary HCO₃⁻ secretion serves to maintain an alkaline pH near the apical surface of cholangiocytes by forming a HCO₃⁻ "umbrella". In this alkaline environment, glycine conjugated bile salts (which are predominant in man), with a pKa of ~4, remain deprotonated and are unable to permeate the apical membrane and cause cell damage. Functional impairment of biliary HCO₃⁻ secretion leads to enhanced vulnerability of cholangiocytes toward the attack of hydrophobic bile salts, causing cell damage and cholangitis. Such an impairment could be due to genetic factors, like mutations of the anion exchanger 2 (a variant of the Cl⁻/HCO₃⁻ exchanger) in primary biliary cirrhosis or of TGR5 (a bile salt receptor implicated in the regulation of HCO₃⁻ secretion) in primary sclerosing cholangitis. This stimulating hypothesis is amenable to experimental testing and has potential pathophysiological and therapeutic implications.

Primary biliary cirrhosis and autoimmune hepatitis: apotopes and epitopes

Autoimmune liver diseases (ALDs) represent a wide spectrum of chronic inflammatory diseases that are characterized by an immune-mediated attack against either hepatocytes (in the case of autoimmune hepatitis types 1 and 2, AIH-1, 2) or cholangiocytes (in primary biliary cirrhosis, PBC). PBC is considered a model autoimmune disease due to the homogeneity of patients, the high specificity of antimitochondrial antibodies (AMAs), and the specificity of biliary epithelial cell (BEC) destruction. It ensues from a multi-lineage loss of tolerance to the E2 component of the pyruvate dehydrogenase complex (PDC-E2). One of the major unanswered questions in the pathogenesis of PBC is the specificity of small intrahepatic bile duct attack while PDC-E2 is present in mitochondria of nucleated cells. Recent findings suggest that the apoptosis of BECs may be of considerable importance for understanding PBC, and that they are more than simply an innocent victim of an immune attack. Rather, they attract immune attack by virtue of the unique biochemical mechanisms by which they handle PDC-E2. The role of apoptotic cells in AIH is not well defined, but advances in the study of autoreactive T cells stem mostly from AIH type 2, where the main autoantigen (CYP2D6) is known, enabling the characterization of antigen-specific immune responses. This review article is intended to provide a critical overview of current evidence on tissue specificity in ALDs, as well as the characteristics of the relevant epitopes and apotopes and their biological and clinical significance.

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.

The soluble CTLA-4 receptor and its role in autoimmune diseases: an update

CTLA-4, initially described as a membranebound molecule, is a costimulatory receptor transducing a potent inhibitory signal. Increasing evidence shows the CTLA-4 gene to be an important susceptibility locus for autoimmune endocrinopathies and other autoimmune disorders. A soluble form of cytotoxic T-lymphocyte-associated antigen-4 (sCTLA-4) has been established and shown to possess CD80/CD86 binding activity and in vitro immunoregulatory functions. sCTLA-4 is generated by alternatively spliced mRNA. Whereas low levels of sCTLA-4 are detected in normal human serum, increased serum levels are observed in several autoimmune diseases (e.g. Graves’ disease, myasthenia gravis, systemic lupus erythematosus, type 1 diabetes, systemic sclerosis, coeliac disease, autoimmune pancreatitis and primary biliary cirrhosis). The biological significance of increased sCTLA-4 serum levels is not fully clarified yet. On the one hand, it can be envisaged that sCTLA-4 specifically inhibits early T-cell activation by blocking the interaction of CD80/CD86 with the costimulatory receptor CD28. On the other hand, higher levels of sCTLA-4 could compete for the binding of the membrane form of CTLA-4 with CD80/CD86 in the later phases of T-lymphocyte activation, causing a reduction in inhibitory signalling. This double-edged nature of sCTLA-4 to block the binding of CD28 to CD80/CD86 may result in different outcomes during the clinical course of an autoimmune disease.

Hepatic granulomas: pathogenesis and differential diagnosis

Granulomatous liver disease constitutes a category of hepatic disorders and is at present diagnosed in approximately 4% of liver biopsies. Hepatic granulomas develop through the interactions of T lymphocytes and macrophages, with the integral involvement of T-helper (T(H)) 1 or T(H)2 pathways or both, depending on the specific granulomatous disease. Hepatic granulomas may be manifested clinically by elevated levels of serum alkaline phosphatase and g-glutamyltransferase enzymes, damage to specific structures (eg, intrahepatic bile ducts in primary biliary cirrhosis), or infrequently, progressive liver disease with portal hypertension and cirrhosis (eg, sarcoidosis). Systemic immunologic disorders, infectious diseases, drug hepatotoxicity, and reaction to neoplastic disease are the major causative factors responsible for granulomas in the liver. These causes and recent epidemiologic trends are covered in this discussion.

Increased ΤGF-β3 in primary biliary cirrhosis: an abnormality related to pathogenesis?

AIM

To investigate the transforming growth factor-β (TGF-β) isoforms in the peripheral and hepatic venous blood of primary biliary cirrhosis (PBC) patients.

METHODS

We examined TGF-β1, TGF-β2 and TGF-β3 (enzyme-linked immunosorbent assay), in 27 stage IV PBC patients (27 peripheral and 15 hepatic vein sera), 35 early (I-II) PBC and 60 healthy controls. As disease controls 28 hepatitis C virus (HCV) cirrhosis (28 peripheral and 17 hepatic vein serum), 44 chronic HCV hepatitis and 38 HCV-related hepatocellular carcinomas were included. We also tested liver tissue by immunohistochemistry to identify localization of TGF isoforms.

RESULTS

TGF-β1 was significantly decreased in all cirrhotics (PBC III-IV: median 13.4 ng/mL; range, 7.4-26.2, HCV cirrhosis: 11.6 ng/mL; range, 5.0-33.8), compared to controls (30.9 ng/mL; range, 20.9-37.8). TGF-β2 was increased in viral cirrhosis but not in PBC and chronic hepatitis. TGF-β3 (47.2 pg/mL; range, 27.0-79.7 in healthy controls) was increased in early and late PBC (I-II: 94.3 pg/mL; range, 41.5-358.6; III-IV: 152.8 pg/mL; range, 60.4-361.2; P < 0.001) and decreased in viral cirrhosis (37.4 pg/mL; range, 13.3-84.0; P < 0.05). Hepatic vein TGF-β levels were analogous to those in peripheral blood. Immunohistochemistry identified all isoforms in portal tract lymphocytes, sinusoidal cells and cholangiocytes. TGF-β3 was additionally overexpressed in hepatocytes in PBC patients.

CONCLUSION

The serum profile of TGF-β isoforms is different in cirrhotics. Increased TGF-β3 is characteristic of PBC. These findings may be related to the immunological abnormalities of PBC.

Primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is an idiopathic chronic autoimmune liver disease that primarily affects women. It is believed that the aetiology for PBC is a combination between environmental triggers in genetically vulnerable persons. The diagnosis for PBC is made when two of the three criteria are fulfilled and they are: (1) biochemical evidence of cholestatic liver disease for at least 6 month's duration; (2) anti-mitochondrial antibody (AMA) positivity; and (3) histologic features of PBC on liver biopsy. Ursodeoxycholic acid (UDCA) is the only FDA-approved medical treatment for PBC and should be administered at a recommended dose of 13-15 mg/kg/day. Unfortunately despite adequate dosing of UDCA, approximately one-third of patients does not respond adequately and may require liver transplantation. Future studies are necessary to elucidate the role of environmental exposures and overall genetic impact not only in the development of PBC, but on disease progression and variable clinical response to therapy.

The biliary HCO(3)(-) umbrella: a unifying hypothesis on pathogenetic and therapeutic aspects of fibrosing cholangiopathies

This review focuses on the hypothesis that biliary HCO(3)(-) secretion in humans serves to maintain an alkaline pH near the apical surface of hepatocytes and cholangiocytes to prevent the uncontrolled membrane permeation of protonated glycine-conjugated bile acids. Functional impairment of this biliary HCO(3)(-) umbrella or its regulation may lead to enhanced vulnerability of cholangiocytes and periportal hepatocytes toward the attack of apolar hydrophobic bile acids. An intact interplay of hepatocellular and cholangiocellular adenosine triphosphate (ATP) secretion, ATP/P2Y- and bile salt/TGR5-mediated Cl(-)/ HCO(3)(-) exchange and HCO(3)(-) secretion, and alkaline phosphatase-mediated ATP breakdown may guarantee a stable biliary HCO(3)(-) umbrella under physiological conditions. Genetic and acquired functional defects leading to destabilization of the biliary HCO(3)(-) umbrella may contribute to development and progression of various forms of fibrosing/sclerosing cholangitis.

Association analysis of cytotoxic T-lymphocyte antigen 4 gene polymorphisms with primary biliary cirrhosis in Japanese patients

BACKGROUND & AIMS

Primary biliary cirrhosis (PBC) is an organ-specific autoimmune disease of still unidentified genetic etiology that is characterized by chronic inflammation of the liver. Since cytotoxic T-lymphocyte antigen 4 (CTLA4) polymorphisms have recently been linked with PBC susceptibility in studies on Caucasians, we investigated the genetic association between CTLA4 polymorphisms and PBC in a Japanese population.

METHODS

Five single nucleotide polymorphisms (SNPs) in the CTLA4 gene (rs733618, rs5742909, rs231775, rs3087243, and rs231725) were genotyped in 308 patients with PBC and 268 healthy controls using a TaqMan assay.

RESULTS

One CTLA4 gene SNP (rs231725) was significantly associated with susceptibility to anti-mitochondrial antibody (AMA)-positive PBC, but clinical significance disappeared after correction for multiple testing. Moreover, CTLA4 gene SNPs did not influence AMA development or disease progression to orthotopic liver transplantation in our Japanese cohort. In haplotype analyses, one haplotype [haplotype 1 (CGGA)] at rs5742909, rs231775, rs3087243, and rs231725, was significantly associated with susceptibility to both AMA-positive PBC and overall PBC.

CONCLUSIONS

This study showed that CTLA4 gene polymorphisms had a modest, but significant association with susceptibility to PBC in the Japanese population. The connection between genetic variants and the function of the CTLA4 gene remains to be addressed in future investigations.

Genome-wide meta-analyses identify three loci associated with primary biliary cirrhosis

A genome-wide association screen for primary biliary cirrhosis risk alleles was performed in an Italian cohort. The results from the Italian cohort replicated IL12A and IL12RB associations, and a combined meta-analysis using a Canadian dataset identified newly associated loci at SPIB (P = 7.9 x 10(-11), odds ratio (OR) = 1.46), IRF5-TNPO3 (P = 2.8 x 10(-10), OR = 1.63) and 17q12-21 (P = 1.7 x 10(-10), OR = 1.38).

Phenotypical and functional alterations of CD8 regulatory T cells in primary biliary cirrhosis

The mechanisms that lead to loss of tolerance in autoimmune disease have remained both elusive and diverse, including both genetic predisposition and generic dysregulation of critical mononuclear cell subsets. In primary biliary cirrhosis (PBC), patients exhibit a multilineage response to the E2 component of pyruvate dehydrogenase involving antibody as well as autoreactive CD4 and CD8 responses. Recent data from murine models of PBC have suggested that a critical mechanism of biliary destruction is mediated by liver-infiltrating CD8 cells. Further, the number of autoreactive liver-infiltrating CD4 and CD8 cells is significantly higher in liver than blood in patients with PBC. Based on this data, we have studied the frequencies and phenotypic characterization of both CD4 and CD8 regulatory T cell components in both patients with PBC and age-sex matched controls. Our data is striking and indicate that CD8 Treg populations from PBC patients, but not controls, have significant phenotypic alterations, including increased expression of CD127 and reduced CD39. Furthermore, in vitro induction of CD8 Tregs by incubation with IL10 is significantly reduced in PBC patients. Importantly, the frequencies of circulating CD4+CD25+ and CD8+ and CD28- T cell subpopulations are not significantly different between patients and controls. In conclusion, these data identify the CD8 Treg subset as a regulatory T cell subpopulation altered in patients with PBC.

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.

Stigma and Liver Disease

This study explores stigma experienced by women with the autoimmune liver disease Primary Biliary Cirrhosis (PBC). Liver disease is commonly stigmatized due to an association with alcoholism and drug abuse, and persons with PBC may be subjected to stigma even though there is no etiological connection to substance use. Women with PBC (25 waiting list, 75 posttransplant), recruited through an online organization and two transplant centers, completed a survey regarding demographic, biomedical, psychological, and social contributors to overall quality of life (QOL). Two measures of stigma were analyzed in relation to the other variables and QOL. Open-ended questions concerned stigmatizing experiences and participants' reactions to them. Almost one in five reported experiencing stigmatizing behaviors from others, in particular from medical professionals, that resulted in hurt and anger. Higher stigma scores were associated with diminished mental and social dimensions of QOL as well as with greater uncertainty about illness, more symptoms from the disease and medication effects. Depression, fatigue, and age (younger) were key predictors of stigma. Those experiencing stigma should receive support and access to counseling. The knowledge and sensitivity of the public and medical professionals regarding the damage inflicted by stigmatizing any disease should be addressed through professional continuing education programs and public campaigns by organizations that support people with chronic liver disease.

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.

The PXR is a drug target for chronic inflammatory liver disease

PXR activators are used to treat pruritus in chronic inflammatory liver diseases such as primary biliary cirrhosis (PBC). The aims of this study were to determine whether PXR activators could have an additional benefit of inhibiting inflammation in the liver, and determine whether cyclosporin A - which more effectively prevents PBC recurrence in transplanted patients than FK506 - is a PXR activator. In SJL/J mice (which have constitutively high levels of hepatic portal tract inflammatory cell recruitment), feeding a PXR activator inhibited inflammation, TNFalpha and Il-1alpha mRNA expression in SJL/J-PXR(+/+), but not SJL/J-PXR(-/-). Monocytic cells - a major source of inflammatory mediators such as TNFalpha - expressed the PXR and PXR activators inhibited endotoxin-induced NF-kappaB activation and TNFalpha expression. PXR activation also inhibited endotoxin-stimulated TNFalpha secretion from liver monocytes/macrophages isolated from PXR(+/+) mice, but not from cells isolated from PXR(-/-) mice. To confirm that PXR activation inhibits NF-kappaB in vivo, 3x-kappaB-luc fibrotic mice (which express a luciferase gene regulated by NF-kappaB) were imaged after treatment with the hepatotoxin CCl(4). PXR activator inhibited the induction of hepatic NF-kappaB activity without affecting CCl(4) toxicity/hepatic damage. Using a PXR reporter gene assay, cyclosporin A - but not FK506 - was shown to be a direct PXR activator, and also to induce expression of the classic PXR-regulated CYP3A4 gene in human hepatocytes and in a cell line null for the FXR, a nuclear receptor with similar properties to the PXR.

CONCLUSION

PXR activation is anti-inflammatory in the liver and the effects of cyclosporin A in PBC disease recurrence may be mediated in part via the PXR. Since PXR activation promotes hepatocyte growth and is also anti-fibrogenic, the PXR may be an excellent drug target for the treatment of chronic inflammatory liver disease.

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.

Cyclosporine A protects against primary biliary cirrhosis recurrence after liver transplantation

Primary biliary cirrhosis (PBC) reoccurs in a proportion of patients following liver transplantation (LT). The aims of our study were to evaluate the risk factors associated with PBC recurrence and determine whether recurrent disease constitutes a negative predictor for survival. One hundred and eight patients receiving LT for end-stage PBC were studied. Recurrent disease was diagnosed in 28 patients (26%). Probability of recurrent PBC at 5 years was 13% and 29% at 10 years with an overall incidence of 3.97 cases per 100 patient years. By univariate Cox analysis use of tacrolimus (HR 6.28, 95% CI, 2.44-16.11, p < 0.001) and mycophenolate mofetil (HR 5.21, 95% CI, 1.89-14.33, p = 0.001) were associated with higher risk of recurrence; whereas use of cyclosporine A (CsA) and azathioprine were associated with reduced risk of recurrence (HR 0.13, 95% CI 0.05-0.35, p < 0.001 and HR 0.27, 95% CI 0.11-0.64, p = 0.003, respectively). In the multivariate Cox analysis, only CsA was independently associated with protection against recurrence (HR 0.17, 95% CI 0.06-0.71, p = 0.02). Five-year probability of survival was 83% and 96%, in patients without and with recurrence (log-rank test, p = 0.3). Although PBC transplant recipients receiving CsA have a lower risk of disease recurrence, the development of recurrent PBC did not impact on long-term patient survival.

A2BP1 as a novel susceptible gene for primary biliary cirrhosis in Japanese patients

Primary biliary cirrhosis (PBC) is a complex autoimmune liver disease with an etiology that remains to be conclusively elucidated. As such, we screened the human genome for genes that might influence PBC susceptibility or resistance using 400 microsatellite markers. A strong candidate gene indicated by susceptibility microsatellite markers was further evaluated by association analysis using single nucleotide polymorphisms (SNPs). A total of 126 patients with PBC and 95 healthy Japanese controls were enrolled. Four candidate susceptible regions and seven candidate protective regions were statistically associated with PBC. Because the D16S423 marker on chromosome 16p showed the strongest evidence of linkage, the protein-coding gene ataxin 2-binding protein 1 (A2BP1) lying 27 kb on the centromeric side of D16S423 was targeted as a candidate susceptible gene. Seven SNPs (rs17139207, rs12926282, rs17139244, rs6500742, rs4146812, rs4124065, and rs889699) in the A2BP1 gene were genotyped in patients and controls. The rs17139244 SNP was found to be weakly associated with PBC in an additive model. The genotype frequency of the major C allele at rs6500742 was significantly associated with PBC, compared with healthy controls. This study showed a total of 11 candidate PBC susceptibility or resistance regions. In particular, the A2BP1 gene might play a pivotal role for susceptibility to PBC.

Geoepidemiology of autoimmune liver diseases

Autoimmune liver diseases are characterized by immune mediated injury of bile ducts or hepatocytes, thus including cholangiopathies such as primary biliary cirrhosis, primary sclerosing cholangitis, and immunoglobulin G4-associated cholangitis, and autoimmune hepatitis. Although the liver was one of the earliest recognized sites of autoimmune aggression, the aetiology of autoimmune liver diseases remains largely obscure and their clinical management still difficult. Since an ever increasing applicability of immunology to a wide variety of chronic diseases, basic and clinical knowledge on autoimmune liver diseases grow rapidly in the last few years. This review will mainly focus on the available geoepidemiology data of these disorders, but it will deal also on their main clinical characteristics, as well as mechanisms of etiopathogenesis, for each of the above diseases, together with their overlap forms. In particular, we will discuss the major underlying immunomolecular mechanisms of development, the genetic influences, the growing number of immuno-serological diagnostic markers, and the increasingly effective therapeutic possibilities.

Beta-glucosylceramide ameliorates liver inflammation in murine autoimmune cholangitis

We have demonstrated spontaneous development of autoimmune cholangitis, similar to human primary biliary cirrhosis, in mice expressing a dominant negative form of the transforming growth factor-beta receptor (dnTGF-betaRII) restricted to T cells. The autoimmune cholangitis appears to be mediated by autoreactive CD8(+) T lymphocytes that home to the portal tracts and biliary system. Because the liver pathology is primarily secondary to CD8(+) T cells, we have determined herein whether administration of beta-glucosylceramide (GC), a naturally occurring plant glycosphingolipid, alters the natural history of disease in this model. We chose GC because previous work has demonstrated its ability to alter CD8(+) T cell responses and to down-regulate tissue inflammation. Accordingly, dnTGF-betaRII mice were treated with either GC or control for a period of 18 weeks beginning at 6 weeks of age. Importantly, in mice that received GC, there was a significant decrease in the frequency and absolute number of autoreactive liver-infiltrating CD8(+) T cells, accompanied by a significant decrease in activated CD44(high) CD8(+) T cell populations. Further, there was a significant reduction in portal inflammation in GC-treated mice. Interestingly, there were no changes in anti-mitochondrial antibodies, CD4(+) T cells, CD19(+) B cells or natural killer (NK) T cell populations, indicating further that the beneficial effects of GC on liver inflammation were targeted specifically to liver-infiltrating CD8(+) T cells. These data suggest that further work on GC in models of CD8(+) T-mediated inflammation are needed and point to a new therapeutic venue for potentially treating and/or modulating autoimmune disease.

New molecular insights into the mechanisms of cholestasis

Recent progress in basic research has enhanced our understanding of the molecular mechanisms of normal bile secretion and their alterations in cholestasis. Genetic transporter variants contribute to an entire spectrum of cholestatic liver diseases and can cause hereditary cholestatic syndromes or determine susceptibility and disease progression in acquired cholestatic disorders. Cholestasis is associated with complex transcriptional and post-transcriptional alterations of hepatobiliary transporters and enzymes participating in bile formation. Ligand-activated nuclear receptors for bile acids and other biliary compounds play a key role in the regulation of genes required for bile formation. Pharmacological interventions in cholestasis may aim at modulating such novel regulatory pathways. This review will summarize the principles of molecular alterations in cholestasis and will give an overview of potential clinical implications.

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.

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.

Lymphocyte recruitment and homing to the liver in primary biliary cirrhosis and primary sclerosing cholangitis

The mechanisms operating in lymphocyte recruitment and homing to liver are reviewed. A literature review was performed on primary biliary cirrhosis (PBC), progressive sclerosing cholangitis (PSC), and homing mechanisms; a total of 130 papers were selected for discussion. Available data suggest that in addition to a specific role for CCL25 in PSC, the CC chemokines CCL21 and CCL28 and the CXC chemokines CXCL9 and CXCL10 are involved in the recruitment of T lymphocytes into the portal tract in PBC and PSC. Once entering the liver, lymphocytes localize to bile duct and retain by the combinatorial or sequential action of CXCL12, CXCL16, CX3CL1, and CCL28 and possibly CXCL9 and CXCL10. The relative importance of these chemokines in the recruitment or the retention of lymphocytes around the bile ducts remains unclear. The available data remain limited but underscore the importance of recruitment and homing.

Primary biliary cirrhosis associated with HLA, IL12A, and IL12RB2 variants

BACKGROUND

Primary biliary cirrhosis is a chronic granulomatous cholangitis, characteristically associated with antimitochondrial antibodies. Twin and family aggregation data suggest that there is a significant genetic predisposition to primary biliary cirrhosis, but the susceptibility loci are unknown.

METHODS

To identify genetic loci conferring a risk for primary biliary cirrhosis, we carried out a genomewide association analysis in which DNA samples from 2072 Canadian and U.S. subjects (536 patients with primary biliary cirrhosis and 1536 controls) were genotyped for more than 300,000 single-nucleotide polymorphisms (SNPs). Sixteen of the SNPs most strongly associated with primary biliary cirrhosis were genotyped in two independent replication sets. We carried out fine-mapping studies across three loci associated with primary biliary cirrhosis.

RESULTS

We found significant associations between primary biliary cirrhosis and 13 loci across the HLA class II region; the HLA-DQB1 locus (encoding the major histocompatibility complex class II, DQ beta chain 1) had the strongest association (P=1.78x10(-19); odds ratio for patients vs. controls, 1.75). Primary biliary cirrhosis was also significantly and reproducibly associated with two SNPs at the IL12A locus (encoding interleukin-12alpha), rs6441286 (P=2.42x10(-14); odds ratio, 1.54) and rs574808 (P=1.88x10(-13); odds ratio, 1.54), and one SNP at the IL12RB2 locus (encoding interleukin-12 receptor beta2), rs3790567 (P=2.76x10(-11); odds ratio, 1.51). Fine-mapping analysis showed that a five-allele haplotype in the 3' flank of IL12A was significantly associated with primary biliary cirrhosis (P=1.15x10(-34)). We found a modest genomewide association (P<5.0x10(-5)) with the risk of disease for SNPs at the STAT4 locus (encoding signal transducer and activator of transcription 4) and the CTLA4 locus (encoding cytotoxic T-lymphocyte-associated protein 4) and 10 other loci.

CONCLUSIONS

Our data show significant associations between primary biliary cirrhosis and common genetic variants at the HLA class II, IL12A, and IL12RB2 loci and suggest that the interleukin-12 immunoregulatory signaling axis is relevant to the pathophysiology of primary biliary cirrhosis. (ClinicalTrials.gov number, NCT00242125.)

Immune-mediated liver diseases: programmed cell death ligands and circulating apoptotic markers

Primary biliary cirrhosis, primary sclerosing cholangitis and autoimmune hepatitis are the three major immune-mediated liver diseases. The etiologies of primary biliary cirrhosis, primary sclerosing cholangitis and autoimmune hepatitis are largely unknown, but seem to be influenced by genetic and environmental factors. Autoantibodies can be found in nearly all patients with primary sclerosing cholangitis and autoimmune hepatitis, and in the vast majority of patients with primary sclerosing cholangitis. In addition, autoimmune hepatitis is associated with high concentrations of serum globulins. Enhanced liver cell death by apoptosis has been described in all of these liver diseases, although the precise mechanisms remain unclear. In general, apoptosis can be initiated via an extrinsic pathway that is triggered by engagement of death receptors on the cell surface, or via an intrinsic pathway that is induced by mitochondrial injury and is influenced by members of the Bcl-2 family. In both pathways, effector caspases are finally activated that cleave and degrade cell structures, resulting in the release of apoptotic products into the circulation. New diagnostic tests can detect these apoptotic markers and programmed cell death ligands such as Fas and Fas-ligands, nucleosomes, caspases, cytokeratin fragments, macrophage migration inhibitory factor, soluble intracellular adhesion molecule, natural killer cells group 2D and programmed death ligands. Several of these markers have been found to be altered in tissue and/or blood of immune-mediated liver diseases, some also in nonimmune-mediated liver diseases. Beyond their potential usefulness as additional diagnostic markers, they may be valuable for the estimation of disease severity and therapy monitoring. This review summarizes current knowledge on apoptotic mechanisms, death receptor ligands and circulating apoptotic markers in immune-mediated liver diseases.

Vitamin D receptor polymorphisms are associated with increased susceptibility to primary biliary cirrhosis in Japanese and Italian populations

BACKGROUND/AIMS

Vitamin D receptor (VDR) agonists have recently been identified as potent immunomodulators capable of inhibiting Th1-mediated immune response, leading us to consider the hypothesis that functional VDR polymorphisms might contribute to enhanced risk for developing primary biliary cirrhosis (PBC), a Th1-mediated autoimmune disease. In the current study, we aimed at elucidating the genetic association of VDR polymorphisms with susceptibility to PBC in Japanese and Italian populations.

METHODS

We enrolled 334 PBC patients (195 Japanese and 139 Italians), as well as 334 age- and sex-matched controls (179 Japanese and 156 Italians). VDR genotyping was performed by PCR-RFLP, using BsmI, ApaI and TaqI endonucleases.

RESULTS

The genotype BB of BsmI polymorphism was significantly associated with PBC (OR = 1.80 [95% CI; 1.19-2.73], p = 0.005). The association of the genotype BB was observed in Japanese (OR = 13.77, p = 0.001), and Italians (OR = 1.83, p = 0.019), respectively, although not significant in Italians after Bonferroni correction. The frequency of the B allele at the BsmI polymorphism was significantly higher in PBC patients (OR = 1.27 [95% CI; 1.02-1.59], p = 0.040).

CONCLUSIONS

The genotype 'BB' as well as 'B' allele at BsmI polymorphism of the VDR gene contribute to the risk of PBC development.

The serological profile of the autoimmune hepatitis/primary biliary cirrhosis overlap syndrome

OBJECTIVES

During the last decade patients with concomitant clinical, biochemical, immunoserological, and histological features of both autoimmune hepatitis (AIH) and primary biliary cirrhosis (PBC) were sporadically described, but definite diagnostic criteria and specific serological markers to support the diagnosis of AIH/PBC overlap syndrome (AIH/PBC OS) are still lacking.

METHODS

Clinical, biochemical, and histological features, autoantibody profile, and treatment response of 15 patients with coexistent hepatitic and cholestatic liver damage, all fulfilling strict diagnostic criteria for both AIH and PBC, were compared with those of 120 patients with pure PBC and 120 patients with pure AIH.

RESULTS

At diagnosis, the AIH/PBC OS patients' median age was 51 years, similar to that of the PBC patients (52 years, P=NS), but significantly higher than that of the AIH patients (40 years, P=0.04). Anti-dsDNA antibodies were detected in 60% of AIH/PBC OS patients, but only in 4% of PBC patients and 26% of AIH patients (P<0.0001 and 0.01, respectively). Double positivity for antimitochondrial antibodies (AMA) and anti-dsDNA was present in 47% of those with AIH/PBC OS, but only in 2% of the pathological controls (P<0.0001; specificity: 98; 95% confidence interval (CI): 97-99.2; positive likelihood ratio: 28; 95% CI: 9.8-79.4). Combined therapy (ursodeoxycholic acid (UDCA) plus steroids) achieved biochemical response in 77% of AIH/PBC OS patients.

CONCLUSIONS

Concomitant AMA/anti-dsDNA seropositivity can be considered the serological profile of AIH/PBC OS. The combination of UDCA and steroids is effective in achieving persistent biochemical amelioration in most AIH/PBC OS patients.

Primary biliary cirrhosis is associated with altered hepatic microRNA expression

MicroRNAs (miRNAs) are small RNA molecules that negatively regulate protein coding gene expression and are thought to play a critical role in many biological processes. Aberrant levels of miRNAs have been associated with numerous diseases and cancers, and as such, miRNAs have gain much interests as diagnostic biomarkers, and as therapeutic targets. However, their role in autoimmunity is largely unknown. The aims of this study are to: (1) identify differentially expressed miRNAs in human primary biliary cirrhosis (PBC); (2) validate these independently; and (3) identify potential targets of differentially expressed miRNAs. We compared the expression of 377 miRNAs in explanted livers form subjects with PBC versus controls with normal liver histology. A total of 35 independent miRNAs were found to be differentially expressed in PBC (p < 0.001). Quantitative PCR was employed to validate down-regulation of microRNA-122a (miR-122a) and miR-26a and the increased expression of miR-328 and miR-299-5p. The predicted targets of these miRNAs are known to affect cell proliferation, apoptosis, inflammation, oxidative stress, and metabolism. Our data are the first to demonstrate that PBC is characterized by altered expression of hepatic miRNA; however additional studies are required to demonstrate a causal link between those miRNA and the development of PBC.

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.

Crosstalk of liver, bile ducts and the gut

A complex interplay of liver, bile ducts, and the gut critically determines functioning of these organs in health and disease. Biochemical and physiological aspects of their interaction and the role of inflammatory cells, cytokines, bile acids, visceral hormones, neuropeptides and other messengers in the pathogenesis of model immune-mediated hepatobiliary disorders are discussed in the actual issue of Clinical Reviews in Allergy and Immunology. Potential molecular targets for future therapeutic approaches are also addressed.

Induction of autoimmune cholangitis in non-obese diabetic (NOD).1101 mice following a chemical xenobiotic immunization

Our laboratory has suggested that loss of tolerance to pyruvate dehydrogenase (PDC-E2) leads to an anti-mitochondrial antibody response and autoimmune cholangitis, similar to human primary biliary cirrhosis (PBC). We have suggested that this loss of tolerance can be induced either via chemical xenobiotic immunization or exposure to select bacteria. Our work has also highlighted the importance of genetic susceptibility. Using the non-obese diabetic (NOD) congenic strain 1101 (hereafter referred to as NOD.1101 mice), which has chromosome 3 regions from B6 introgressed onto a NOD background, we exposed animals to 2-octynoic acid (2OA) coupled to bovine serum albumin (BSA). 2OA has been demonstrated previously by a quantitative structural activity relationship to react as well as or better than lipoic acid to anti-mitochondrial antibodies. We demonstrate herein that NOD.1101 mice immunized with 2OA-BSA, but not with BSA alone, develop high titre anti-mitochondrial antibodies and histological features, including portal infiltrates enriched in CD8(+) cells and liver granulomas, similar to human PBC. We believe this model will allow the rigorous dissection of early immunogenetic cause of biliary damage.

Deficiency in regulatory T cells results in development of antimitochondrial antibodies and autoimmune cholangitis

There have been several descriptions of mouse models that manifest select immunological and clinical features of autoimmune cholangitis with similarities to primary biliary cirrhosis in humans. Some of these models require immunization with complete Freund's adjuvant, whereas others suggest that a decreased frequency of T regulatory cells (Tregs) facilitates spontaneous disease. We hypothesized that antimitochondrial antibodies (AMAs) and development of autoimmune cholangitis would be found in mice genetically deficient in components essential for the development and homeostasis of forkhead box 3 (Foxp3)(+) Tregs. Therefore, we examined Scurfy (Sf) mice, animals that have a mutation in the gene encoding the Foxp3 transcription factor that results in a complete abolition of Foxp3(+) Tregs. At 3 to 4 weeks of age, 100% of animals exhibit high-titer serum AMA of all isotypes. Furthermore, mice have moderate to severe lymphocytic infiltrates surrounding portal areas with evidence of biliary duct damage, and dramatic elevation of cytokines in serum and messenger RNAs encoding cytokines in liver tissue, including tumor necrosis factor alpha, interferon-gamma, interleukin (IL)-6, IL-12, and IL-23.

CONCLUSION

The lack of functional Foxp3 is a major predisposing feature for loss of tolerance that leads to autoimmune cholangitis. These findings reflect on the importance of regulatory T cells in other murine models as well as in patients with primary biliary cirrhosis.

Current status of therapy in autoimmune liver disease

Therapeutic strategies for autoimmune liver diseases are increasingly established. Although proportionately uncommon, specialist centers have with time refined the best approaches for each disease, based on an improved understanding of the spectrum of presentation. The major treatment aims are to prevent end-stage liver disease and its associated complications. As a result of drugs such as ursodeoxycholic acid, predniso(lo)ne and azathioprine, both primary biliary cirrhosis and autoimmune hepatitis are now less commonly indications for liver transplantation. Unfortunately, the same inroads in treatment efficacy have as yet not been made for primary sclerosing cholangitis, although the recognition that a subset of patients may have a treatable secondary sclerosing cholangitis (IgG4 related) is helping a proportion. With better biological understanding, more specific interventions are expected that will benefit all those with autoimmune liver diseases.

Differential mechanisms in the pathogenesis of autoimmune cholangitis versus inflammatory bowel disease in interleukin-2Ralpha(-/-) mice

Interleukin-2 (IL-2) receptor alpha knockout (IL-2Ralpha(-/-)) mice have a deficiency of CD25 and a corresponding functional defect in T regulatory cells (Tregs). These mice spontaneously develop portal inflammation with biliary ductular damage and colitis with features similar to human inflammatory bowel disease with T cell infiltrates in both the liver and colon. In humans, inflammatory bowel disease may be accompanied by primary sclerosing cholangitis (PSC), but seldom primary biliary cirrhosis (PBC). We hypothesized that the effector mechanism responsible for T cell infiltrates would differ for colon versus liver. To address this thesis, we developed three colonies of double-knockout mice including IL-2Ralpha(-/-) CD4(-/-), IL-2Ralpha(-/-) CD8(-/-), and IL-2Ralpha(-/-) T cell receptor (TCR)-beta(-/-). Tissue immunopathology, body weight, and serum levels of cytokines, immunoglobulins, and anti-mitochondrial antibodies (AMA) were assayed at 3 months of age. Relative to IL-2Ralpha(-/-) mice, IL-2Ralpha(-/-) CD4(-/-) mice had increased biliary ductular damage but reduced inflammation in the colon. In contrast, IL-2Ralpha(-/-) CD8(-/-) mice had increased colon inflammation but markedly attenuated biliary ductular damage. Both IL-2Ralpha(-/-) CD4(-/-) and IL-2Ralpha(-/-) CD8(-/-) mice demonstrated elevated serum levels of tumor necrosis factor alpha (TNF-alpha), interferon gamma (IFN-gamma), interleukin-12p40 (IL-12p40), and interleukin-2 (IL-2) compared with C57BL/6J controls, but only IL-2Ralpha(-/-) CD8(-/-) mice had increased serum levels of immunoglobulin A (IgA), AMA and interleukin-17 (IL-17). Finally, and of importance, IL-2Ralpha(-/-) TCR-beta(-/-) mice had abrogation of liver and colon pathological conditions and lacked AMA. In conclusion, on loss of Treg function in mice, CD8 T cells mediate biliary ductular damage whereas CD4 T cells mediate induction of colon-specific autoimmunity.