PBC screen: an IgG/IgA dual isotype ELISA detecting multiple mitochondrial and nuclear autoantibodies specific for primary biliary cirrhosis

High levels of soluble CTLA-4 are present in anti-mitochondrial antibody positive, but not in antibody negative patients with primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is a chronic autoimmune cholestatic liver disease frequently characterized by anti-mitochondrial autoantibodies (AMA). A minority of patients are AMA-negative. Cytotoxic-T-Lymphocyte-Antigen-4 (CTLA-4) is a surface molecule expressed on activated T-cells delivering a critical negative immunoregulatory signal. A soluble form of CTLA-4 (sCTLA-4) has been detected at high concentrations in several autoimmune diseases, and its possible functional meaning has been suggested. We aimed to evaluate sCTLA-4 concentration in sera of patients with PBC and to correlate it to immunological abnormalities associated with the disease. Blood samples were collected from 82 PBC-patients diagnosed according to international criteria (44 AMA-positive/MIT3-positive and 38 AMA-negative-MIT3-negative), and 65 controls. sCTLA-4 levels were evaluated by ELISA and Western blot. Increased sCTLA-4 concentrations were found in all AMA-positive PBC-patients, but in none of the AMA-negative ones, nor in normal controls or in controls with unrelated liver diseases. sCTLA-4 presence was associated with autoantibodies against MIT3, but not with nuclear autoantibodies (sp100, gp210). This is the first study to demonstrate that levels of sCTLA-4 are elevated in sera of PBC patients. However, they are clearly restricted to patients with AMA positivity, suggesting an immunological difference with respect to AMA-negative ones.

Gastrointestinal involvement in systemic sclerosis

Systemic sclerosis is an autoimmune chronic disease characterised by microvascular, muscular and immunologic abnormalities that lead to progressive and systemic deposition of connective tissue in the skin and internal organs. The gastrointestinal tract is often overlooked by physicians but it is the most affected organ after the skin, from the mouth to the anus. Indeed, 80% of SSc patients may present with gastrointestinal involvement. Gastrointestinal manifestations range from bloating and heartburn to dysphagia and anorectal dysfunction to severe weight loss and malabsorption. However, the gastrointestinal involvement is rarely the direct cause of death, but has great impact on quality of life and leads to several comorbidities that subsequently affect patients' survival. Treatments, including nutritional support and prokinetics provide limited benefits and do not arrest the progressive course of the disease, but earlier detection of gastrointestinal involvement may reduce the risk of complications such as malnutrition.

Meta-analysis assessment of GP210 and SP100 for the diagnosis of primary biliary cirrhosis

PURPOSE

To conduct a systematic review of included studies assessing the association of GP210 and SP100 with the risk of primary biliary cirrhosis (PBC) using meta-analysis.

METHODS

Five databases, the Cochrane Library, MEDLINE, VIP, CNKI, WANFANG were used to detect the role of GP210 and SP100 in diagnosis of PBC. Approximately 13,000 participants from several countries were included in this analysis. Meta-DiSc statistical software was used for analysis.

RESULTS

25 studies on GP210 and 21 studies on SP100 were included in the meta-analysis. The DOR, sensitivity, specificity of GP210 in diagnosis of PBC were 24.854 (11.957-51.660), 0.272 (0.257-0.288), 0.985 (0.982-0.988), respectively, and they were 9.133 (4.739-17.600), 0.231 (0.213-0.249), 0.977 (0.973-0.981) for SP100.

CONCLUSION

Our meta-analysis indicated both GP210 and SP100 had high specificity but low sensitivity in diagnosis of PBC.

Escherichia coli infection induces autoimmune cholangitis and anti-mitochondrial antibodies in non-obese diabetic (NOD).B6 (Idd10/Idd18) mice

Several epidemiological studies have demonstrated that patients with primary biliary cirrhosis (PBC) have a higher incidence of urinary tract infections (UTI) and there is significant homology of the immunodominant mitochondrial autoantigen, the E2 component of the pyruvate dehydrogenase complex (PDC-E2), between mammals and bacteria. Previous work has demonstrated that non-obese diabetic (NOD).B6 Idd10/Idd18 infected with Novosphingobium aromaticivorans developed liver lesions similar to human PBC. It was postulated that the biliary disease was dependent upon the presence of the unique N. aro glycosphingolipids in activating natural killer T (NK T) cells. To address this issue, we infected NOD.B6 Idd10/Idd18 mice with either Escherichia coli, N. aro or use of a phosphate-buffered saline (PBS) vehicle control and serially followed animals for the appearance of liver pathology and anti-mitochondrial autoantibodies (AMA). Of striking importance, the biliary disease of E. coli-infected mice was more severe than N. Aro-infected mice and the titre of AMA was higher in E. coli-infected mice. Furthermore, the immunopathology did not correlate with the ability of bacterial extracts to produce antigen-dependent activation of NK T cells. Our data suggest that the unique glycosphingolipids of N. aro are not required for the development of autoimmune cholangitis. Importantly, the data highlight the clinical significance of E. coli infection in a genetically susceptible host, and we suggest that the appearance of autoimmune cholangitis is dependent upon molecular mimicry. These data highlight that breach of tolerance to PDC-E2 is probably the first event in the natural history of PBC in genetically susceptible hosts.

Review article: controversies in the management of primary biliary cirrhosis and primary sclerosing cholangitis

BACKGROUND

Despite considerable advances over the last two decades in the molecular understanding of cholestasis and cholestatic liver disease, little improvement has been made in diagnostic tools and therapeutic strategies.

AIMS

To critically review controversial aspects of the scientific basis for common clinical practice in primary biliary cirrhosis (PBC) and primary sclerosing cholangitis (PSC) and to discuss key ongoing challenges to improve patient management.

METHODS

We performed a literature search using PubMed and by examining the reference lists of relevant review articles related to the clinical management of PBC and PSC. Articles were considered on the background of the European Association for the Study of the Liver (EASL) and the American Association for the Study of Liver Diseases (AASLD) practice guidelines and clinical experience of the authors.

RESULTS

Ongoing challenges in PBC mainly pertain to the improvement of medical therapy, particularly for patients with a suboptimal response to ursodeoxycholic acid. In PSC, development of medical therapies and sensitive screening protocols for cholangiocarcinoma represent areas of intense research. To rationally improve patient management, a better understanding of pathogenesis, including complications like pruritis and fatigue, is needed and there is a need to identify biomarker end-points for treatment effect and prognosis. Timing of liver transplantation and determining optimal regimens of immunosuppression post-liver transplantation will also benefit from better appreciation of pre-transplant disease mechanisms.

CONCLUSION

Controversies in the management of PBC and PSC relate to topics where evidence for current practice is weak and further research is needed.

Tracing environmental markers of autoimmunity: introducing the infectome

We recently introduced the concept of the infectome as a means of studying all infectious factors which contribute to the development of autoimmune disease. It forms the infectious part of the exposome, which collates all environmental factors contributing to the development of disease and studies the sum total of burden which leads to the loss of adaptive mechanisms in the body. These studies complement genome-wide association studies, which establish the genetic predisposition to disease. The infectome is a component which spans the whole life and may begin at the earliest stages right up to the time when the first symptoms manifest, and may thus contribute to the understanding of the pathogenesis of autoimmunity at the prodromal/asymptomatic stages. We provide practical examples and research tools as to how we can investigate disease-specific infectomes, using laboratory approaches employed from projects studying the “immunome” and “microbiome”. It is envisioned that an understanding of the infectome and the environmental factors that affect it will allow for earlier patient-specific intervention by clinicians, through the possible treatment of infectious agents as well as other compounding factors, and hence slowing or preventing disease development.

Novel method for ANA quantitation using IIF imaging system

A variety of antinuclear antibodies (ANAs) are found in the serum of patients with autoimmune diseases. The detection of abnormal ANA titers is a critical criterion for diagnosis of systemic lupus erythematosus (SLE) and other connective tissue diseases. Indirect immunofluorescence assay (IIF) on HEp-2 cells is the gold standard method to determine the presence of ANA and therefore provides information about the localization of autoantigens that are useful for diagnosis. However, its utility was limited in prognosing and monitoring of disease activity due to the lack of standardization in performing the technique, subjectivity in interpreting the results and the fact that it is only semi-quantitative. On the other hand, ELISA for the detection of ANA can quantitate ANA but could not provide further information about the localization of the autoantigens. It would be ideal to integrate both of the quantitative and qualitative methods. To address this issue, this study was conducted to quantitatively detect ANAs by using IIF imaging analysis system. Serum samples from patients with ANA positive (including speckled, homogeneous, nuclear mixture and cytoplasmic mixture patterns) and negative were detected for ANA titers by the classical IIF and analyzed by an image system, the image of each sample was acquired by the digital imaging system and the green fluorescence intensity was quantified by the Image-Pro plus software. A good correlation was found in between two methods and the correlation coefficients (R(2)) of various ANA patterns were 0.942 (speckled), 0.942 (homogeneous), 0.923 (nuclear mixture) and 0.760 (cytoplasmic mixture), respectively. The fluorescence density was linearly correlated with the log of ANA titers in various ANA patterns (R(2)>0.95). Moreover, the novel ANA quantitation method showed good reproducibility (F=0.091, p>0.05) with mean±SD and CV% of positive, and negative quality controls were equal to 126.4±9.6 and 7.6%, 10.4±1.25 and 12.0%, respectively. In conclusion, our novel ANA quantitation method can provide both of the fluorescence density, which could precisely reflect the fluctuate of ANAs level in patient's serum and the useful information about the localization of the autoantigens for clinician in diagnosing and monitoring diseases.

Diagnostic and clinical significance of anti-centromere antibodies in primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is an autoimmune disease of the liver characterised by biochemical evidence of cholestasis, elevated alkaline phosphatase levels and the presence of the highly disease specific anti-mitochondrial autoantibodies. Extra-hepatic autoimmune manifestations are common, including rheumatic disorders, such as systemic sclerosis (SSc). Notably, PBC is the most frequent autoimmune liver disease in SSc patients. Based on skin lesion extension, two major SSc disease subgroups are recognised: limited cutaneous SSc (lSSc) and diffuse cutaneous SSc. Anti-centromere antibody (ACA) positivity is highly characteristic of SSc, with up to 90% prevalence in lSSc patients. ACA has also been found in up to 30% of PBC patients and 80% of patients with a PBC/SSc overlap syndrome. The diagnostic and clinical significance of ACA positivity in patients with PBC without SSc has recently been under investigation, with several studies highlighting links to severe bile duct injury and portal hypertension. This review discusses the diagnostic and clinical relevance of ACA in patients with PBC, with or without SSc.

Clinical significance of the fluctuation of primary biliary cirrhosis-related autoantibodies during the course of the disease

Primary biliary cirrhosis (PBC) is a chronic cholestatic disease characterized by the presence of antimitochondrial antibodies (AMA). PBC-specific antinuclear antibodies (ANA) have been characterized and associated with disease progression and outcome. We evaluated the clinical significance of the presence and serial changes in titers of AMA, PBC-specific ANA (anti-gp210, anti-sp100) and anti-chromatin antibodies. Over a median (IQR) period of 35 (36) months, 512 specimens were collected from 110 patients. Autoantibodies were detected by commercial ELISAs (INOVA Diagnostics). Biochemical, clinical, and histological status were included at initial presentation and during follow-up visits. The Mayo risk score was calculated as a prognostic index at each time point. Liver biopsy findings were classified according to Ludwig's classification and biochemical response to ursodeoxycholic acid was evaluated according to Pares. At baseline, AMA IgG and IgA, anti-gp210 IgG, anti-sp100 IgG and anti-chromatin IgG were detected in 92/110 (83.6%), 57/110 (51.8%), 5/110 (4.5%), 14/110 (12.7%), and 0/110 (0%) patients, respectively. Positivity for all autoantibodies apart from anti-chromatin, at baseline visit (n = 110 patients), in all tested sera (n = 512) as well as increased autoantibodies titers during follow-up were associated with biochemically and/or histologically advanced disease. A decrease of anti-sp100 titers but not of anti-gp210 titers during follow-up was associated with improvement of Mayo risk score (p = 0.025) and response to ursodeoxycholic acid (p = 0.016). These results suggest that detection of AMA and PBC-specific ANA was correlated with disease severity. Serial changes of anti-sp100 titers and not of anti-gp210 titers might prove useful for monitoring the disease course and treatment outcome.

Vitamin D in autoimmune liver disease

The development of autoimmune disease is based on the interaction of genetic susceptibility and environmental causes. Environmental factors include infectious and non-infectious agents, with some of these factors being implicated in several autoimmune diseases. Vitamin D is now believed to play a role in the development (or prevention) of several autoimmune diseases, based on its immunomodulatory properties. As well, the increasing incidence of autoimmune disease as one moves away from the equator, may be due to the lack of sunlight, which is crucial for the maintenance of normal vitamin D levels. A deficiency in vitamin D levels or vitamin D receptors is commonly indicated in autoimmune diseases, with multiple sclerosis (MS) being one of the best-studied and well-known examples. However, the role of vitamin D in other autoimmune diseases is not well defined, including autoimmune liver diseases such as primary biliary cirrhosis, autoimmune hepatitis, and primary sclerosing cholangitis. This review will examine the role of vitamin D as an immunomodulator, followed by a comparison of vitamin D in MS versus autoimmune liver disease. From this comparison, it will become clear that vitamin D likely plays a role in the development of autoimmune liver disease, but this area requires further investigation.

Primary biliary cirrhosis-specific antimitochondrial antibodies in neonatal haemochromatosis

Background and Aim. Neonatal hemochromatosis (NH) is characterised by severe liver injury and extrahepatic siderosis sparing the reticuloendothelial system. Its aetiology is obscure, although it has been proposed as an alloimmune disease, resulting from immunological reaction to self-antigens (alloantigens) which the body recognizes as foreign. We studied an infant with NH and his mother whose sera contained antimitochondrial antibody (AMA), the hallmark of primary biliary cirrhosis (PBC). Material and Methods. To investigate the origin of AMA in the infant, we studied isotype distributions in serum from the mother and infant. Serum samples were obtained at diagnosis of NH, after liver transplantation (LT; age 1 month), and over the ensuing 17 months. Results. At NH diagnosis, infant and maternal serum contained AMA of the IgG isotype, predominantly of the G3 and G1 subclasses. AMA strongly reacted against the pyruvate dehydrogenase complex E2 subunit (PDC-E2), the major PBC-specific AMA autoantigen. Anti-PDC-E2 responses in both infant and mother declined over time, being present 2 months after LT (mother and child) and absent 10 months later (mother) and 17 months later (child). Conclusion. The association of maternally transferred IgG1 and IgG3 subclass AMA with the appearance of liver damage in an infant with NH may suggest a causal link between antibody and liver damage.

The limitations and hidden gems of the epidemiology of primary biliary cirrhosis

Epidemiology is expected to provide important clues to our understanding of the enigmatic etiopathogenesis of primary biliary cirrhosis (PBC). First, a systematic review of population based studies indicated a wide range in the yearly incidence (0.33-5.8/100.000) and point prevalence (1.91-40.2/100.000) rates. Though different ethnic representations may also contribute it is likely that methodological issues, based on the retrospective survey of diagnosed cases, and time trend play a major role, also in view of the prolonged asymptomatic period of the disease. Of note, the highest prevalence rates (35-40/100.000) were found in areas characterized by high medical awareness and easier access to healthcare. Second, the search for serum AMA in unselected population sera may identify the largest possible number of patients who have or will develop the disease. Indeed, a surprisingly high AMA prevalence rate, ranging between 0.43 and 1%, appears likely in the general population despite the lack of adequate work-up in most studies. Third, the median female to male ratio for PBC is classically accepted as 9-10:1 but is significantly lower for AMA prevalence (2.5:1), death certificates for PBC (4.3:1) and liver transplantation (6:1), thus suggesting that PBC in men may be underdiagnosed in early stages or manifest a more severe progression. Lastly, studies of both PBC and serum AMA prevalence among family members and monozygotic twins strongly support the role played by genetic factors in the etiopathogenesis of the disease. In conclusion, PBC epidemiology is far from being a closed case and the numerous open issues will be solved through a collaborative effort and powerful data mining tools.

Liver auto-immunology: the paradox of autoimmunity in a tolerogenic organ

The study of the liver as a lymphoid organ is a growing field fueled by our better knowledge of the different component of the immune system and how they orchestrate an immune-related response. The liver have highly specialized mechanisms of immune tolerance, mainly because is continuously exposed to microbial and environmental antigens, and dietary components from the gut. Accordingly, the liver contains specialized lymphoid subpopulations acting as antigen-presenting cells. Growing evidences show that the liver is also associated with obesity-associated diseases because of its immune-related capacity to sense metabolic stress induced by nutritional surplus. Finally, the liver produces a pletora of neo-antigens being the primary metabolic organ of the body. Common immune mechanisms play a key pathogenetic role in most of acute and chronic liver diseases and in the rejection of liver allografts. Any perturbations of liver-related immune functions have important clinical implications. This issue of the Journal of Autoimmunity is focused on the more recent advances in our knowledge related to the loss of liver tolerance, a paradox for a tolerogenic organ, that leads to overactivation of the innate and adaptive immune response and the development of autoimmune liver diseases, such as autoimmune hepatitis, primary biliary cirrhosis, and primary sclerosing cholangitis. The invited expert review articles capture the underlying immunomolecular mechanisms of the development and progression of autoimmune liver diseases, the novel field of the immune-related "liver-gut" axis influences to the development of liver autoimmunity, the predominant role of genetic factors, and the increasingly effective immuno-therapeutic possibilities.

The immunophysiology and apoptosis of biliary epithelial cells: primary biliary cirrhosis and primary sclerosing cholangitis

Biliary epithelial cells (BECs) provide the first line of defense against lumenal microbes in the biliary system. BECs express a variety of pathogen recognition receptors and can activate several intracellular signaling cascades to initiate antimicrobial defenses, including production of several anti-microbial peptides, cytokines, chemokines, and adhesion molecules. BECs also secrete immunoglobulin A and interact with other cells through expression and release of adhesion molecules and immune mediators. Recently, several reports suggest a correlation between apoptosis and autoimmunity through ineffective clearance of self-antigens. Primary biliary cirrhosis (PBC) is a slowly progressive, autoimmune cholestatic liver disease characterized by highly specific antimitochondrial antibodies (AMAs) and the specific immune-mediated destruction of BECs. We have demonstrated that the AMA self-antigen, namely the E2 subunit of the pyruvate dehydrogenase complex, is detectable in its antigenically reactive form within apoptotic blebs from human intrahepatic biliary epithelial cells and activates innate immune responses. Primary sclerosing cholangitis (PSC) is a chronic cholestatic liver disease characterized by inflammation and the presence of concentric fibrosis of intrahepatic and/or extrahepatic bile ducts, eventually leading to cirrhosis. However, apoptosis does not appear to play a central role in PSC. Despite both diseases involving immune-mediated injury to bile ducts, apoptosis occurs more commonly overall in PBC where it likely plays a unique role.

Antimitochondrial antibody heterogeneity and the xenobiotic etiology of primary biliary cirrhosis

Antimitochondrial antibodies (AMAs) directed against the lipoyl domain of the E2 subunit of pyruvate dehydrogenase (PDC-E2) are detected in 95% of patients with primary biliary cirrhosis (PBC) and are present before the onset of clinical disease. The recent demonstration that AMAs recognize xenobiotic modified PDC-E2 with higher titers than native PDC-E2 raises the possibility that the earliest events involved in loss of tolerance are related to xenobiotic modification. We hypothesized that reactivity to such xenobiotics would be predominantly immunoglobulin M (IgM) and using sera from a large cohort of PBC patients and controls (n = 516), we examined in detail sera reactivity against either 6,8-bis(acetylthio) octanoic acid (SAc)-conjugated bovine serum albumin (BSA), recombinant PDC-E2 (rPDC-E2) or BSA alone. Further, we also defined the relative specificity to the SAc moiety using inhibition enzyme-linked immunosorbent assay (ELISA); SAc conjugate and rPDC-E2-specific affinity-purified antibodies were also examined for antigen specificity, isotype, and crossreactivity. Reactivity to SAc conjugates is predominantly IgM; such reactivity reflects a footprint of previous xenobiotic exposure. Indeed, this observation is supported by both direct binding, crossreactivity, and inhibition studies. In both early and late-stage PBC, the predominant Ig isotype to SAc is IgM, with titers higher with advanced stage disease. We also note that there was a higher level of IgM reactivity to SAc than to rPDC-E2 in early-stage versus late-stage PBC. Interestingly, this finding is particularly significant in light of the structural similarity between SAc and the reduced form of lipoic acid, a step which is similar to the normal physiological oxidation of lipoic acid.

CONCLUSION

Specific modifications of the disulfide bond within the lipoic-acid-conjugated PDC-E2 moiety, i.e., by an electrophilic agent renders PDC-E2 immunogenic in a genetically susceptible host.

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

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

Detection of anti-SP100 antibodies in primary biliary cirrhosis. Comparison of ELISA and immunofluorescence

Primary biliary cirrhosis (PBC) is, which a chronic, autoimmune liver disease. Some patients have antinuclear antibodies anti-Sp100, which are considered to be disease-specific. We compared an enzyme-linked immunosorbent assay (ELISA) and indirect immunofluorescence (IIF) for detection of anti-Sp100. The sensitivity of anti-Sp100 determined by ELISA and IIF was 44% and 34%, respectively. Specificity was 99% for ELISA and 98% for IIF, respectively. The positive and negative predictive value (PPV, NPV) for anti-Sp100 determined by ELISA were 98%, 60% and 95%, 56% for IIF respectively. IIF required substantial experience in interpreting subjective patterns, whereas ELISA was more sensitive, cheaper, less time consuming, and produced clear-cut quantitative results.

Infectome: a platform to trace infectious triggers of autoimmunity

The "exposome" is a term recently used to describe all environmental factors, both exogenous and endogenous, which we are exposed to in a lifetime. It represents an important tool in the study of autoimmunity, complementing classical immunological research tools and cutting-edge genome wide association studies (GWAS). Recently, environmental wide association studies (EWAS) investigated the effect of environment in the development of diseases. Environmental triggers are largely subdivided into infectious and non-infectious agents. In this review, we introduce the concept of the "infectome", which is the part of the exposome referring to the collection of an individual's exposures to infectious agents. The infectome directly relates to geoepidemiological, serological and molecular evidence of the co-occurrence of several infectious agents associated with autoimmune diseases that may provide hints for the triggering factors responsible for the pathogenesis of autoimmunity. We discuss the implications that the investigation of the infectome may have for the understanding of microbial/host interactions in autoimmune diseases with long, pre-clinical phases. It may also contribute to the concept of the human body as a superorganism where the microbiome is part of the whole organism, as can be seen with mitochondria which existed as microbes prior to becoming organelles in eukaryotic cells of multicellular organisms over time. A similar argument can now be made in regard to normal intestinal flora, living in symbiosis within the host. We also provide practical examples as to how we can characterise and measure the totality of a disease-specific infectome, based on the experimental approaches employed from the "immunome" and "microbiome" projects.

Serum autoantibodies for the diagnosis and management of autoimmune liver diseases

The spectrum of autoimmune liver diseases (AILD) includes primary biliary cirrhosis, primary sclerosing cholangitis and autoimmune hepatitis. The immunological mechanisms triggering the initiation and perpetuation of AILD remains unknown, while autoantigens are now recognized in most cases, and are generally nontraditional in their widespread distribution. Sensitive and specific methods for the detection of serum autoantibodies in patients affected by AILD represent a challenge for researchers and clinicians who desire to obtain an early and certain diagnosis as well as markers of disease control. To this regard, the use and interpretation of serum autoantibodies in AILD may be seen as paradigmatic for the large gaps in our knowledge based on the lack of true population-based studies. The present review article will critically discuss the available evidence on the use of autoantibody findings in the diagnosis or management of autoimmune liver disease.

The X-factor in primary biliary cirrhosis: monosomy X and xenobiotics

Primary biliary cirrhosis (PBC) is a chronic, cholestatic, autoimmune liver disease characterised by the destruction of small- and medium-sized bile ducts. The serological hallmark of PBC includes antimitochondrial antibodies (AMA). The disease has a striking female predominance, and primarily affects women of middle-age. First-degree relatives, and in particular female relatives, are known to have an increased risk of developing the disease. Several studies have attempted to explain the female predominance of PBC, and autoimmune diseases in general. Two components that are of interest in PBC include monosomy X and xenobiotics. Monosomy X has been noted to be prevalent in the peripheral blood mononuclear cells of PBC patients. Xenobiotics, which are exogenous chemicals not normally found within the body, have been implicated in the modification of, and loss of, tolerance to AMA. Several cosmetics are known to contain these xenobiotics, which is of interest given the information provided in regards to known risk factors for PBC development. This review will focus on X monosomy and xenobiotics, which appear to constitute the X-factor of PBC.

Asialoglycoprotein receptor (ASGPR) as target autoantigen in liver autoimmunity: lost and found

Asialoglycoprotein receptor (ASGPR) has attracted the attention of liver immunologists for many years. This liver-specific lectin was found to be a major B and T cell autoantigenic target in patients with autoimmune liver diseases, and in particular in autoimmune hepatitis (AIH). This review discusses the biological significance of ASGPR and its relevance to the pathogenesis of autoimmune and virus-triggered liver diseases. We also discuss emerging data on the diagnostic and clinical relevance of anti-ASGPR antibodies in light of recent reports based on commercially available anti-ASGPR enzyme-linked immunosorbent assays. Finally, we critically revisit the data reporting on disease-specific cellular immune responses against ASGPR and their relevance in relation to the pathogenesis of AIH.

Popular and unpopular infectious agents linked to primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is a progressive cholestatic liver disease characterized by the autoimmune destruction of the biliary epithelial cells of the small and medium-size bile ducts. The disease affects middle aged women and usually affects more than one member within a family. The pathognomonic serological hallmark of the disease is the presence of circulating anti-mitochondrial antibodies, and disease-specific anti-nuclear antibodies. Susceptibility genes and environmental risk factors such as infections and smoking have been reported as important for the development of the disease. Among the environmental agents, infectious triggers are the best studied. Most of the work published so far has investigated the role of infections caused by Novosphingobium aromaticivorans and Escherichia coli. This review will discuss the popular and unpopular infectious agents causatively linked to PBC. It will also examine reports investigating the epidemiological aspects of the disease and their direct or indirect implications to bacterial-induced PBC.

TRAF1 gene polymorphism correlates with the titre of Gp210 antibody in patients with primary biliary cirrhosis

Background. Polymorphisms of TRAF1 (Tumor necrosis factor receptor-associated factor 1) are associated with rheumatoid arthritis (RA). Whether TRAF1 polymorphisms confer increased risk for primary biliary cirrhosis (PBC), an autoimmune liver disease which can co-exist with RA, is unknown. Aim of the Study. To assess the frequency of the RA-conferring susceptibility TRAF1 polymorphisms rs3761847 and rs2900180 in a cohort of PBC patients. The association of TRAF1 polymorphisms with clinical features and autoantibody markers was also analyzed. Methods. We studied 179 PBC patients and 300 controls. Samples were genotyped for TRAF1 gene polymorphisms by real-time PCR. Autoantibodies were tested by ELISA. Results. The frequency of rs3761847 and rs2900180 polymorphisms did not differ between patients and controls. Laboratory or clinical features were not associated with specific polymorphisms. Gp210 autoantibody titres were conspicuously higher among GG homozygotes of rs3761847 as compared with AA homozygotes (P = 0.02). In contrast, antichromatin titers were higher in AA compared to GG rs3761847 homozygotes (P = 0.04). Rheumatoid factor IgG titres were significantly higher in rs2900180 TT homozygotes than CC homozygotes (P = 0.02). Conclusions. TRAF1 polymorphisms occur with the similar frequency in PBC patients and in the general population, but their presence is probably involved in the regulation of specific PBC-related autoantibodies.

Predicting and preventing autoimmunity: the case of anti-mitochondrial antibodies

To be able to predict who will develop autoimmune disease would allow for early treatment which may dramatically alter the course of the disease. In some cases, it may also lead to prevention of the disease development. The prediction of disease development is based on the analysis of risk factors which have been associated with the disease in question. These factors include genetic susceptibility, as well as immunological and environmental factors. One autoimmune disease that may serve as a model for disease prediction is primary biliary cirrhosis (PBC), an autoimmune liver disease affecting the small- and medium-sized bile ducts. PBC could be an ideal model due to recent advances in elucidating its genetic associations. As well, a variety of immunological and environmental risk factors have been well established. Indeed, the presence of PBC-specific antimitochondrial antibodies and/or antinuclear antibodies has been shown to be predictor of disease development and possibly prognosis. This review will examine the current evidence which suggests that we may potentially be able to predict the development of PBC in some individuals. These concepts may also be applied to autoimmune diseases in general.

Role for mycobacterial infection in pathogenesis of primary biliary cirrhosis?

Primary biliary cirrhosis (PBC) is a progressive cholestatic liver disease characterized by the immune-mediated destruction of biliary epithelial cells in small intrahepatic bile ducts. The disease is characterized by circulating antimitochondrial antibodies (AMAs) as well as disease-specific antinuclear antibodies, cholestatic liver function tests, and characteristic histological features, including granulomas. A variety of organisms are involved in granuloma formation, of which mycobacteria are the most commonly associated. This has led to the hypothesis that mycobacteria may be involved in the pathogenesis of PBC, along with other infectious agents. Additionally, AMAs are found in a subgroup of patients with mycobacterial infections, such as leprosy and pulmonary tuberculosis. Antibodies against species-specific mycobacterial proteins have been reported in patients with PBC, but it is not clear whether these antibodies are specific for the disease. In addition, data in support of the involvement of the role of molecular mimicry between mycobacterial and human mitochondrial antigens as triggers of cross-reactive immune responses leading to the loss of immunological tolerance, and the induction of pathological features have been published. Thus, antibodies against mycobacterial heat shock protein appear to cross-recognize AMA-specific autoantigens, but it is not clear whether these autoantibodies are mycobacterium-species-specific, and whether they are pathogenic or incidental. The view that mycobacteria are infectious triggers of PBC is intriguing, but the data provided so far are not conclusive.

Xenobiotics and autoimmunity: does acetaminophen cause primary biliary cirrhosis?

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

Diagnostic and clinical utility of antibodies against the nuclear body promyelocytic leukaemia and Sp100 antigens in patients with primary biliary cirrhosis

BACKGROUND

The lack of an immunoassay that detects antibodies to promyelocytic leukaemia (PML) protein, the primary biliary cirrhosis (PBC)-specific multiple nuclear dot (MND) antigen, has prompted us to develop a line immunoassay (LIA) for the simultaneous detection of PML and Sp100 MND-specific autoantibodies.

METHODS

PML and Sp100 were expressed in Escherichia coli, and analysed by SDS-PAGE and immunoblotting using a monoclonal antibody and MALDI-ToF fingerprinting. A quantitative PML and Sp100 LIA were developed and testing was performed in 150 anti-mitochondrial antibody (AMA) positive, 20 AMA-PBCs and 130 controls.

RESULTS

Thirty-five (23%) of 150 AMA+ PBCs (18 anti-MND+) were anti-PML+ (12%) or anti-Sp100+ (20%), 10 being anti-PML+/Sp100+, 5 single anti-PML+ and 20 single anti-Sp100+. Six (30%, 5 anti-MND+) AMA-PBCs were anti-PML+ or Sp100+. Only 2 (1.7%) pathological controls were anti-PML+ and/or anti-Sp100+. Levels of anti-PML correlated with those of anti-Sp100 (R=0.64, p<0.0001). The autoantibody profile largely remained unchanged over a 10year-follow up (52 patients, 352 samples). Anti-PML, Sp100 or MND-reactive PBCs were younger and had longer disease duration than the seronegative (p=0.06, for both). Anti-Sp100 levels correlated with the Mayo risk score (r=0.63, p=0.01). Anti-PML+/Sp100+ patients had more advanced disease compared to patients negative for anti-PML/Sp100 (p=0.04).

CONCLUSION

The new line immunoassay offers a robust and accurate method for the detection of clinically-relevant PBC-specific anti-MND antibodies.

Autoimmunity and environment: am I at risk?

The complex interplay between environmental factors and genetic susceptibility plays an essential role in disease pathogenesis. This is especially true for autoimmunity, where clinical reports, genomic and epidemiological studies, as well as animal models have identified several environmental and genetic risk factors associated with autoimmune disease. The complexity of this relationship is demonstrated by the vast array of environmental factors that have now been implicated in the induction, and possibly the maintenance of autoimmune disease. The multitude of environmental factors implicated includes both infectious and non-infectious agents. Here, we review one specific autoimmune disease, primary biliary cirrhosis (PBC), as a model for environmental risk factors acting in concert with genetic susceptibility in the disease pathogenesis. PBC is an ideal model, as both infectious and non-infectious environmental agents have been identified as risk factors, and their study provides clues for unravelling the pathogenesis of the disease.

Autoimmune hepatitis type 2 associated with an unexpected and transient presence of primary biliary cirrhosis-specific antimitochondrial antibodies: a case study and review of the literature

BACKGROUND

Unlike other autoimmune liver diseases, primary biliary cirrhosis (PBC) has never been reported in early childhood, while type 2 autoimmune hepatitis (AIH) is eminently a paediatric disease.

CASE PRESENTATION

We describe a case of type 2 AIH with serological positivity for PBC-specific anti-mitochondrial antibodies (AMA) in a 3-year old girl. We found this observation intriguing as AMA and indeed an overlap with PBC are virtually absent in Type 2 AIH, a pediatric form of AIH which is distinct precisely because it is characterized by pathognomonic anti-liver kidney microsomal type 1 (LKM-1) showing a remarkable antigen-specificity directed against cytochrome P4502D6. We also review the literature in relation to AMA positivity in paediatric age and adolescence. In our case, the presence of AIH-2-specific anti-LKM-1 and PBC-specific AMA was confirmed by indirect immunofluorescence (IIF), and immunoblotting and ELISA based on recombinant mitochondrial antigens. The clinical, laboratory and histological features of the child are given in detail. Interestingly the mother was AMA positive without other features of PBC. The child was successfully treated with immunosuppression and five years after the original diagnosis is on a low dose of prednisolone and azathioprine, with no signs of relapse. Anti-LKM-1 antibodies are still present in low titres. AMA were detectable for the first 4 years after the diagnosis and disappeared later.

CONCLUSION

This is the first case report in the literature of AIH type 2 with an unexpected PBC-specific AMA positivity in a young child. Response to immunosuppressive treatment was satisfactory and similar to that described in AIH. A review of published reports on AMA positivity in paediatric age shows that the antibody may arise in the context of immunodeficiency and is variably associated with liver damage.

The role of natural killer (NK) and NK T cells in the loss of tolerance in murine primary biliary cirrhosis

One of the major obstacles in dissecting the mechanism of pathology in human primary biliary cirrhosis (PBC) has been the absence of animal models. Our laboratory has focused on a model in which mice, following immunization with a xenobiotic chemical mimic of the immunodominant autoepitope of the E2 component of pyruvate dehydrogenase complex (PDC-E2), develop autoimmune cholangitis. In particular, following immunization with 2-octynoic acid (a synthetic chemical mimic of lipoic acid-lysine located within the inner domain of PDC-E2) coupled to bovine serum albumin (BSA), several strains of mice develop typical anti-mitochondrial autoantibodies and portal inflammation. The role of innate immune effector cells, such as natural killer (NK) cells and that NK T cells, was studied in this model based on the hypothesis that early events during immunization play an important role in the breakdown of tolerance. We report herein that, following in-vivo depletion of NK and NK T cells, there is a marked suppression of anti-mitochondrial autoantibodies and cytokine production from autoreactive T cells. However, there was no change in the clinical pathology of portal inflammation compared to controls. These data support the hypothesis that there are probably multiple steps in the natural history of PBC, including a role of NK and NK T cells in initiating the breakdown of tolerance. However, the data suggest that adaptive autoimmune effector mechanisms are required for the progression of clinical disease.

The role of natural killer (NK) and NK T cells in the loss of tolerance in murine primary biliary cirrhosis

One of the major obstacles in dissecting the mechanism of pathology in human primary biliary cirrhosis (PBC) has been the absence of animal models. Our laboratory has focused on a model in which mice, following immunization with a xenobiotic chemical mimic of the immunodominant autoepitope of the E2 component of pyruvate dehydrogenase complex (PDC-E2), develop autoimmune cholangitis. In particular, following immunization with 2-octynoic acid (a synthetic chemical mimic of lipoic acid-lysine located within the inner domain of PDC-E2) coupled to bovine serum albumin (BSA), several strains of mice develop typical anti-mitochondrial autoantibodies and portal inflammation. The role of innate immune effector cells, such as natural killer (NK) cells and that NK T cells, was studied in this model based on the hypothesis that early events during immunization play an important role in the breakdown of tolerance. We report herein that, following in-vivo depletion of NK and NK T cells, there is a marked suppression of anti-mitochondrial autoantibodies and cytokine production from autoreactive T cells. However, there was no change in the clinical pathology of portal inflammation compared to controls. These data support the hypothesis that there are probably multiple steps in the natural history of PBC, including a role of NK and NK T cells in initiating the breakdown of tolerance. However, the data suggest that adaptive autoimmune effector mechanisms are required for the progression of clinical disease.

Overcoming a "probable" diagnosis in antimitochondrial antibody negative primary biliary cirrhosis: study of 100 sera and review of the literature

Serum anti-mitochondrial antibodies (AMA) are the serological hallmark of primary biliary cirrhosis (PBC), yet up to 15% of PBC sera are AMA negative at routine indirect immunofluorescence (IIF) while being referred to as "probable" cases. The diagnostic role of PBC-specific antinuclear antibodies (ANA) remains to be determined. We will report herein data on the accuracy of new laboratory tools for AMA and PBC-specific ANA in a large series of PBC sera that were AMA-negative at IIF. We will also provide a discussion of the history and current status of AMA detection methods. We included IIF AMA-negative PBC sera (n=100) and sera from patients with other chronic liver diseases (n=104) that had been independently tested for IIF AMA and ANA; sera were blindly tested with an ELISA PBC screening test including two ANA (gp210, sp100) and a triple (pMIT3) AMA recombinant antigens. Among IIF AMA-negative sera, 43/100 (43%) manifested reactivity using the PBC screening test. The same test was positive for 6/104 (5.8%) control sera. IIF AMA-negative/PBC screen-positive sera reacted against pMIT3 (11/43), gp210 (8/43), Sp100 (17/43), both pMIT3 and gp210 (1/43), or both pMIT3 and Sp100 (6/43). Concordance rates between the ANA pattern on HEp-2 cells and specific Sp100 and gp210 ELISA results in AMA-negative subjects were 92% for nuclear dots and Sp100 and 99% for nuclear rim and gp210. Our data confirm the hypothesis that a substantial part of IIF AMA-negative (formerly coined "probable") PBC cases manifest disease-specific autoantibodies when tested using newly available tools and thus overcome the previously suggested diagnostic classification. As suggested by the recent literature, we are convinced that the proportion of AMA-negative PBC cases will be significantly minimized by the use of new laboratory methods and recombinant antigens.

Epitope-specific anti-nuclear antibodies are expressed in a mouse model of primary biliary cirrhosis and are cytokine-dependent

Although the hallmark of primary biliary cirrhosis (PBC) is the presence of anti-mitochondrial antibodies (AMA), a significant number of patients have anti-nuclear antibodies (ANA) directed primarily against two nuclear proteins, gp210 and sp100. In PBC, there are considerable data on the specificity of these anti-nuclear antibodies as well as suggestive evidence that antibodies to gp210 predict a poor outcome. However, a further understanding of the significance of these autoantibodies has been hampered by limitations in accessing human subjects in a preclinical or early asymptomatic stage. To overcome this limitation, we have taken advantage of transgenic mice with abrogated transforming growth factor-β signalling in T cells (dnTGF-βRII) that develop histological features of PBC as well as the same AMA specificity. We studied these mice for serum ANA, including specific autoantibodies against gp210 and sp100. We further examined sera from dnTGF-βRII mice with concurrent deletions of the genes encoding interleukin (IL)-12p35, IL-12p40, IL-23p19, IL-17, IL-6, interferon (IFN)-γ or tumour necrosis factor (TNF)-α. Sera from all the dnTGF-βRII mouse lines contained antibodies against gp210 and sp100. Of significance, mice with germline deletions of the genes encoding IL-12p40, IL-23p19, IL-17, IL-6 and TNF-α had significantly lower titres of anti-gp210 antibodies. These results provide a platform to dissect the mechanisms of gp210 and sp100 autoantibody production in dnTGF-βRII mice as well as to study the possible role of ANA in the pathophysiology of PBC.

Sex differences associated with primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is a cholestatic liver disease of autoimmune origin, characterised by the destruction of small intrahepatic bile ducts. The disease has an unpredictable clinical course but may progress to fibrosis and cirrhosis. The diagnostic hallmark of PBC is the presence of disease-specific antimitochondrial antibodies (AMA), which are pathognomonic for the development of PBC. The disease overwhelmingly affects females, with some cases of male PBC being reported. The reasons underlying the low incidence of males with PBC are largely unknown. Epidemiological studies estimate that approximately 7–11% of PBC patients are males. There does not appear to be any histological, serological, or biochemical differences between male and female PBC, although the symptomatology may differ, with males being at higher risk of life-threatening complications such as gastrointestinal bleeding and hepatoma. Studies on X chromosome and sex hormones are of interest when studying the low preponderance of PBC in males; however, these studies are far from conclusive. This paper will critically analyze the literature surrounding PBC in males.

Epstein-barr virus as a trigger of autoimmune liver diseases

The pathogenesis of autoimmune diseases includes a combination of genetic factors and environmental exposures including infectious agents. Infectious triggers are commonly indicated as being involved in the induction of autoimmune disease, with Epstein-Barr virus (EBV) being implicated in several autoimmune disorders. EBV is appealing in the pathogenesis of autoimmune disease, due to its high prevalence worldwide, its persistency throughout life in the host's B lymphocytes, and its ability to alter the host's immune response and to inhibit apoptosis. However, the evidence in support of EBV in the pathogenesis varies among diseases. Autoimmune liver diseases (AiLDs), including autoimmune hepatitis (AIH), primary biliary cirrhosis (PBC), and primary sclerosing cholangitis (PSC), have a potential causative link with EBV. The data surrounding EBV and AiLD are scarce. The lack of evidence surrounding EBV in AiLD may also be reflective of the rarity of these conditions. EBV infection has also been linked to other autoimmune conditions, which are often found to be concomitant with AiLD. This paper will critically examine the literature surrounding the link between EBV infection and AiLD development. The current evidence is far from being conclusive of the theory of a link between EBV and AiLD.

Diagnosis and treatment of autoimmune hepatitis

Autoimmune hepatitis is a chronic liver disease characterized by elevated aminotransferase levels, autoantibodies, increased γ-globulin or IgG levels and biopsy evidence of interface hepatitis. Recent advances include new practice guidelines that redefine criteria for remission to require complete biochemical and histological normalization on therapy; comparisons between the revised original and simplified diagnostic scoring systems; refined characterization of autoantibodies and their diagnostic performance parameters; proof of the safety and efficacy of combination budesonide and azathioprine therapy for non-cirrhotic patients; scrutiny of overlap syndromes; further analyses of the outcomes of orthotopic liver transplantation and the diagnosis and treatment of recurrent and de novo autoimmune hepatitis after transplantation. Anticipated consequences of the application of the new definition of therapeutic remission include a reduction in the proportion of patients achieving remission with conventional immunosuppression regimens and a corresponding increase in the need for alternative therapies.

Urinary tract infection as a risk factor for autoimmune liver disease: from bench to bedside

Autoimmune liver diseases include autoimmune hepatitis (AIH), primary biliary cirrhosis (PBC), and primary sclerosing cholangitis. A variety of environmental and genetic risk factors have been associated with these conditions. Recurrent urinary tract infections (rUTI) have been strongly associated with PBC, and to a lesser extent with AIH. These observations were initially based on the observation of significant bacteriuria in female patients with PBC. Larger epidemiological studies demonstrated that there was indeed a strong correlation between recurrent UTI and PBC. AIH has not been linked to recurrent UTI in epidemiological studies; however treatment of UTI with nitrofurantoin can induce AIH. As Escherichia coli is the most prevalent organism isolated in women with UTI, it has been suggested that molecular mimicry between microbial and human PDC-E2 (the main autoantigenic target in PBC) epitopes may explain the link between UTI and PBC. Multiple studies have demonstrated molecular mimicry and immunological cross-reactivity involving microbial and self-antigen mimics. This review will examine the literature surrounding UTI and autoimmune liver disease. This will include case reports and epidemiological studies, as well as experimental data.

Primary biliary cirrhosis and the nuclear pore complex

Experimental models of autoimmune diseases have led to the conclusion that an immune response to nuclear antigens is a sentinel marker for loss of tolerance and potential tissue damage. Various proteins are targets of antinuclear antibodies in a variety of autoimmune diseases, ranging from systemic rheumatologic disorders to diseases affecting specific organs such as the liver. Autoantibodies against specific nuclear constituents have also been used as probes to understand the structure and the function of the targeted components and their relevance to disease pathogenesis. Approximately a quarter of patients with primary biliary cirrhosis (PBC) have antibodies targeting proteins of the nuclear pore complex (NPC), a multi-protein structure that mediates molecular transport across the nuclear envelope. Autoantibodies against the integral membrane glycoprotein gp210 and nucleoporin p62 appear to be highly specific for PBC, an autoimmune disease characterized by progressive destruction of intrahepatic biliary epithelial cells. This review discusses the diagnostic and clinical relevance of anti-NPC antibodies in PBC and the possibility that this autoimmune response may arise as a result of molecular mimicry.

Hair dyes as a risk for autoimmunity: from systemic lupus erythematosus to primary biliary cirrhosis

Environmental and genetic factors appear to be involved in the pathogenesis of primary biliary cirrhosis (PBC), a chronic cholestatic liver disease characterized by immune-mediated destruction of the small and medium sized intrahepatic bile ducts. Environmental factors include exposure to various infectious, xenobiotic and chemical compounds. These exposures may occur occupationally, through water or air contamination, pharmacological administration or by elective exposure, to name a few. Hair dyes are compounds that have been implicated in the development of several autoimmune diseases, including systemic lupus erythematosus (SLE) and PBC. So far, only epidemiological studies have addressed the role of hair dyes in PBC, with limited results. Hair dyes in SLE have been examined, and have recently demonstrated an association, both epidemiologically and immunologically. This follows a series of negative studies, which may not have taken into account several features of hair dye use. This review will examine the literature surrounding hair dye use and SLE, and compare this to data surrounding PBC. Treating physicians should be prepared for questions surrounding the need to take precautions against repeated hair dye use and this topic is discussed further.

Antinuclear antibodies as ancillary markers in primary biliary cirrhosis

Antimitochondrial antibodies are the serological hallmark of primary biliary cirrhosis (PBC). Besides antimitochondrial antibodies, the autoantibody profile of PBC includes antinuclear antibodies (ANA) which are detectable by indirect immunofluorescence in up to 50% of PBC patients. Two immunofluorescence patterns are considered 'PBC-specific': the multiple nuclear dots and rim-like/membranous patterns. The target antigens of the multiple nuclear dots pattern have been identified as Sp100 and promyelocytic leukemia protein, whereas the rim-like/membranous pattern is given by autoantibodies recognizing multiple proteins such as gp210, nucleoporin p62 and the lamin B receptor. Other ANA, especially those already known in the rheumatological setting, such as anticentromere, anti-SSA/Ro and anti-dsDNA antibodies, can be frequently found in PBC, often coexisting in the same patient. In this article, we will report on recent progress in the antigenic characterization of ANA in PBC, their detection with both traditional assays and Western blot/ELISA with molecularly defined nuclear antigens, and we will discuss their clinical significance.

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.

Primary biliary cirrhosis associated with systemic sclerosis: diagnostic and clinical challenges

Patients with primary biliary cirrhosis (PBC) often have concurrent limited systemic sclerosis (SSc). Conversely, up to one-fourth of SSc patients are positive for PBC-specific antimitochondrial antibodies (AMA). The mechanisms responsible for the co-occurrence of these diseases are largely unknown. Genetic, epigenetic, environmental, and infectious factors appear to be important for the pathogenesis of the disease, but the hierarchy of events are not well defined. Patients with SSc and PBC have an increased morbidity and mortality compared with the general population, but whether the presence of both diseases in an affected individual worsens the prognosis and/or outcome of either disease is not clear. Some case reports suggested that the presence of SSc in PBC patents is associated with a more favorable prognosis of the liver disease, whereas others report an increased mortality in patients with PBC and SSc compared to patients with PBC alone. This paper discusses the features of patients with PBC-associated SSc. Our aims are to clarify some of the pathogenetic, diagnostic, and clinical challenges that are currently faced in the routine management of these patients. We also intend to provide some practical hints for practitioners that will assist in the early identification of patients with PBC-associated SSc.

Diagnosis of primary biliary cirrhosis

Primary biliary cirrhosis is the archetypal autoimmune liver disease, with the disease label describing a chronic granulomatous lymphocytic small bile duct cholangitis, which now most commonly presents asymptomatically and at an early pre-cirrhotic stage. Disease is more common than thought, with 1 in 1000 women over the age of 40 affected. Characteristic immunologic features of the disease assist clinicians in ready non-invasive diagnosis of patients, even if asymptomatic with only anicteric/cholestatic liver biochemical profiles. Over 90% of patients are anti-mitochondrial antibody positive, and for those negative, a significant proportion have highly specific anti-nuclear antibody profiles. Liver biopsy remains useful in certain settings where clarity is needed to confirm diagnosis, exclude alternative disease, and assess the relative contribution of PBC to other co-existent liver injury, and seeks to demonstrate in particular the classic bile duct lesions, as well as the degree of interface activity.

Towards systemic sclerosis and away from primary biliary cirrhosis: the case of PTPN22

Primary biliary cirrhosis (PBC) is a chronic cholestatic liver disease characterized by immune-mediated destruction of the small and medium size intrahepatic bile ducts. PBC patients often have concomitant autoimmune diseases, which are most often autoimmune thyroid disease, as well as Sicca syndrome. Occasionally, some PBC patients will also have systemic sclerosis of the limited cutaneous type (lcSSc). Conversely, up to one-fourth of SSc patients are positive for antimitochondrial antibody, the serologic hallmark of PBC. It is also common for SSc patients to have concomitant autoimmune disease, which may include PBC in rare cases. This has led to speculation of shared environmental and/or genetic factors, which lead to the development of PBC in SSc patients and vice versa. Recent genetic studies have revealed associations with several genes in both SSc and PBC. PTPN22 is one gene that has been associated with SSc, but not with PBC. It may be argued that some SSc patients with a particular genotype, which shares genes found in both conditions may develop PBC. Likewise, particular genes such as PTPN22 may infer susceptibility to SSc alone. The presence of PTPN22 may also contribute to the development of SSc in PBC patients. The lack of a large number of overlapping genes may, in part, explain the relative rarity of PBC with SSc and vice versa. This review will examine the literature surrounding the genetic associations of PBC and SSc, and the role of PTPN22 in particular.

Autoimmunity in 2010

There is now growing evidence that autoimmunity is the common trait connecting multiple clinical phenotypes albeit differences in tissue specificity, pathogenetic mechanisms, and therapeutic approaches cannot be overlooked. Over the past years we witnessed a constant growth of the number of publications related to autoimmune diseases in peer-reviewed journals of the immunology area. Original data referred to factors from common injury pathways (i.e. T helper 17 cells, serum autoantibodies, or vitamin D) and specific diseases such as multiple sclerosis, systemic lupus erythematosus, and rheumatoid arthritis. As an example, the issue of a latitudinal gradient in the prevalence and incidence rates has been proposed for all autoimmune diseases and was recently coined as geoepidemiology to suggest new environmental triggers for tolerance breakdown. The present article is aimed at reviewing the articles that were published over the past year in the major autoimmunity and immunology journals.

Epithelial cell specificity and apotope recognition by serum autoantibodies in primary biliary cirrhosis

A major enigma of primary biliary cirrhosis (PBC) is the selective targeting of biliary cells. Our laboratory has reported that after apoptosis, human intrahepatic biliary epithelial cells (HiBECs) translocate the E2 subunit of the pyruvate dehydrogenase complex immunologically intact into apoptotic bodies, forming an apotope. However, the cell type and specificity of this reaction has not been fully defined. To address this issue, we investigated whether the E2 subunit of the pyruvate dehydrogenase complex, the E2 subunit of the branched chain 2-oxo acid dehydrogenase complex, the E2 subunit of the oxo-glutarate dehydrogenase complex, four additional inner mitochondrial enzymes, and four nuclear antigens remain immunologically intact with respect to postapoptotic translocation in HiBECs and three additional control epithelial cells. We report that all three 2-oxo acid dehydrogenase enzymes share the ability to remain intact within the apotope of HiBECs. Interestingly, the E2 subunit of the branched chain 2-oxo acid dehydrogenase complex also remained intact in the other cell types tested. We extended the data, using sera from 95 AMA-positive and 19 AMA-negative patients with PBC and 76 controls, by testing for reactivity against the seven mitochondrial proteins studied herein and also the ability of AMA-negative sera to react with HiBEC apotopes. Sera from 3 of 95 AMA-positive sera, but none of the controls, reacted with 2,4-dienoyl coenzyme A reductase 1, an enzyme also present intact only in the HiBEC apotope, but which has not been previously associated with any autoimmune disease. Finally, the specificity of HiBEC apotope reactivity was confined to AMA-positive sera.

CONCLUSION

We submit that the biliary specificity of PBC is secondary to the unique processes of biliary apoptosis.

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.

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.