Autoimmunity and environment: am I at risk?

Helicobacter pylori antibodies and multiple sclerosis: a single-center study and a short review of the literature

Background

Multiple sclerosis is an immune-mediated disease which has been associated to a great variety of mechanisms that could influence its pathogenesis. Numerous reports in the medical literature suggest that Helicobacter pylori may be a mediator of the disease. However, it is unknown if there is any clear association between MS and HP.

Results

We studied 144 persons with multiple sclerosis prospectively enrolled in our hematopoietic stem cell transplantation program. In 144 persons, 14% patients were positive for IgG-HP whereas 86% were negative, 8.3% pwMS were IgM-HP positive while 91.6% pwMS were negative, 18% patients were positive and 82% negative for IgA-HP. Significantly lower concentrations of anti-HP IgG were found in RRMS in comparison with SPMS (− 28.5, 95% CI 4.3–52.7). While concentrations of anti-HP IgA were significantly lower in SPMS in comparison with RRMS (0.54, 95% CI 0.1–0.9). In a multivariate analysis, positivity rate of anti-HP IgG was found to be higher in SPMS patients (OR 4.7, 95% CI 1.1–19.6).

Conclusions

There was a negative correlation between the presence of anti-HP antibodies and MS. Further larger studies with specific laboratory testing methods are needed to discard or confirm the potential role of anti-HP antibodies as protective for MS.

Association Between Severity of Leptospirosis and Subsequent Major Autoimmune Diseases: A Nationwide Observational Cohort Study

Introduction

Infections play a role in autoimmune diseases (AD). Leptospirosis has been linked to the trigger of systemic lupus erythematosus.

Objective

To investigate subsequent risk of major AD in hospitalized Taiwanese for Leptospirosis.

Methods

Retrospective observational cohort study was employed. The enrolled period was from 2000 to 2012. In the main model, we extracted 4026 inpatients with leptospirosis from the Taiwan National Health Insurance Research Database (NHIRD) and 16,104 participants without leptospirosis at a 1:4 ratio propensity-score matched (PSM) by age, gender, index year, and comorbidities. The follow-up period was defined as the time from the initial diagnosis of leptospirosis to major AD occurrence or 2013. This study was re-analyzed by frequency-matching as a sensitivity analysis for cross-validation. Univariable and multivariable Cox proportional hazards regression models were applied to estimate hazard ratios (HRs) and 95% confidence intervals (CIs).

Results

The adjusted HR (95% CI) of major ADs for the leptospirosis group was 4.45 (3.25–6.79) (p < 0.001) compared to the controls after full adjustment. The risk of major ADs was 5.52-fold (95% CI, 3.82–7.99) higher in leptospirosis patients hospitalized for seven days and above than the controls, while 2.80-fold (95% CI, 1.68–5.61) in those hospitalized less than seven days. The sensitivity analysis yields consistent findings. Stratified analysis revealed that the association between leptospirosis and major ADs was generalized in both genders, and all age groups.

Conclusions

Symptomatic leptospirosis is associated with increased rate of subsequent major ADs, and the risk seems to be higher in severe cases.

Clinical significance of miRNAs in autoimmunity

MicroRNAs (miRNAs) are evolutionally conserved, single-stranded RNAs that regulate gene expression at the posttranscriptional level by disrupting translation. MiRNAs are key players in variety of biological processes that regulate the differentiation, development and activation of immune cells in both innate and adaptive immunity. The disruption and dysfunction of miRNAs can perturb the immune response, stimulate the release of inflammatory cytokines and initiate the production of autoantibodies, and contribute to the pathogenesis of autoimmune diseases, including systemic lupus erythmatosus (SLE), rheumatoid arthritis (RA), primary biliary cholangitis (PBC), and multiple sclerosis (MS). Accumulating studies demonstrate that miRNAs, which can be collected by noninvasive methods, have the potential to be developed as diagnostic and therapeutic biomarkers, the discovery and validation of which is essential for the improvement of disease diagnosis and clinical monitoring. Recently, with the development of detection tools, such as microarrays and NGS (Next Generation Sequencing), large amounts of miRNAs have been identified and suggest a critical role in the pathogenesis of autoimmune diseases. Several miRNAs associated diagnostic biomarkers have been developed and applied clinically, though the pharmaceutical industry is still facing challenges in commercialization and drug delivery. The development of miRNAs is less advanced for autoimmune diseases compared with cancer. However, drugs that target miRNAs have been introduced as candidates and adopted in clinical trials. This review comprehensively summarizes the differentially expressed miRNAs in several types of autoimmune diseases and discusses the role and the significance of miRNAs in clinical management. The study of miRNAs in autoimmunity promises to provide novel and broad diagnostic and therapeutic strategies for a clinical market that is still in its infancy.

Chromosomal Instability in Farmers Exposed to Pesticides: High Prevalence of Clonal and Non-Clonal Chromosomal Alterations

Introduction

An important economic activity in Colombia is agricultural production and farmers are frequently exposed to pesticides. Occupational exposure to pesticides is associated with an increased incidence of various diseases, including cancer, Parkinson’s disease, Alzheimer’s disease, reproductive disorders, and birth defects. However, although high genotoxicity is associated with these chemicals, information about the type and frequency of specific chromosomal alterations (CAs) and the level of chromosomal instability (CIN) induced by exposure to pesticides is scarce or absent.

Methods

In this study, CAs and CIN were assessed in peripheral blood lymphocytes (PBLs) from five farmers occupationally exposed to pesticides and from five unexposed individuals using GTG-banding and molecular cytogenetic analysis.

Results

A significant increase in clonal and non-clonal chromosomal alterations was observed in pesticide-exposed individuals compared with unexposed individuals (510±12,2 vs 73±5,7, respectively; p<0.008). Among all CAs, monosomies and deletions were more frequently observed in the exposed group. Also, a high frequency of fragilities was observed in the exposed group.

Conclusion

Together, these findings suggest that exposure to pesticides could be associated with CIN in PBLs and indicate the need for the establishment of educational programs on safety precautions when handling pesticides, such as wearing gloves, masks and boots, changing clothes and maintaining proper hygiene, among others. Further evaluation in other similar studies that include a greater number of individuals exposed to pesticides is necessary.

Burden of Primary Biliary Cholangitis Among Inpatient Population in the United States

Primary biliary cholangitis (PBC) is an autoimmune liver disease that can lead to cirrhosis and liver failure. Our aim was to assess the recent trends in the mortality rates and health care utilization of patients with PBC seen in the inpatient setting in the United States. We used the National (Nationwide) Inpatient Sample data (2005‐2014). The study population included adults with PBC, using International Classification of Diseases, Ninth Revision codes. Trends in PBC‐related discharges, total charges, length of stay (LoS), and in‐hospital mortality were evaluated. Hierarchical generalized linear models were performed for determining predictors of mortality and total hospital charges. Between the study years of 2005 and 2014, a total of 22,665 hospitalized cases with PBC were identified (mean age 63 years; 84% female, 76% white). The number of PBC‐related discharges increased from 3.24 per 100,000 in 2005 to 3.68 per 100,000 in 2014, with an average annual increase of 1.4% (95% confidence interval [CI]: 0.4%‐2.4%). Fifty‐seven percent had Medicare as their primary payer, 37% had cirrhosis, and 1.3% had hepatocellular carcinoma. Between 2005 and 2014, the average total charges for PBC increased from $53,901 to $57,613 (annual percent change [APC], 1.7%; 95% CI: −0.2%‐3.5%), LoS decreased from 6.9 days to 5.4 days (APC, −2.2%; 95% CI: −3.2% to −1.1%), and mortality rate decreased from 3.8% to 2.8% (APC, −5.4%; 95% CI: −8.4% to −2.4%). Multivariable analysis revealed that ascites were independently associated with increased risk of in‐hospital mortality (odds ratio: 1.77; 95% CI: 1.50‐2.08), increased charge (percent change: 22.5%; 95% CI: 18.6%‐26.7%), and increased LoS (percent change: 29.7%; 95% CI: 25.7%‐33.9%). Conclusion: The number of PBC cases has increased in recent years. Mortality and LoS have decreased, and the total charges have remained the same.

The Role of Invariant NKT in Autoimmune Liver Disease: Can Vitamin D Act as an Immunomodulator?

Natural killer T (NKT) cells are a distinct lineage of T cells which express both the T cell receptor (TCR) and natural killer (NK) cell markers. Invariant NKT (iNKT) cells bear an invariant TCR and recognize a small variety of glycolipid antigens presented by CD1d (nonclassical MHC-I). CD1d-restricted iNKT cells are regulators of immune responses and produce cytokines that may be proinflammatory (such as interferon-gamma (IFN-γ)) or anti-inflammatory (such as IL-4). iNKT cells also appear to play a role in B cell regulation and antibody production. Alpha-galactosylceramide (α-GalCer), a derivative of the marine sponge, is a potent stimulator of iNKT cells and has been proposed as a therapeutic iNKT cell activator. Invariant NKT cells have been implicated in the development and perpetuation of several autoimmune diseases such as multiple sclerosis and systemic lupus erythematosus (SLE). Animal models of SLE have shown abnormalities in iNKT cells numbers and function, and an inverse correlation between the frequency of NKT cells and IgG levels has also been observed. The role of iNKT cells in autoimmune liver disease (AiLD) has not been extensively studied. This review discusses the current data with regard to iNKT cells function in AiLD, in addition to providing an overview of iNKT cells function in other autoimmune conditions and animal models. We also discuss data regarding the immunomodulatory effects of vitamin D on iNKT cells, which may serve as a potential therapeutic target, given that deficiencies in vitamin D have been reported in various autoimmune disorders.

The epigenetics of PBC: The link between genetic susceptibility and environment

Primary biliary cholangitis (PBC) previously known as primary biliary cirrhosis is an autoimmune disease-associated with progressive cholestasis, the presence of autoreactive T cell and characteristic serological autoantibodies. Genetic and genome-wide association studies (GWAS) have recently shed light on the genetic background of PBC. Besides that some causal nucleotide changes and mechanisms remain largely unknown as suggested for example, by the observation that monozygotic twins have an identical DNA sequence even if presents some phenotypic differences that may be consequences of different exposures to environmental stressors. For this reason, it is believed that epigenetic mechanisms may be involved in PBC pathogenesis, as already demonstrated in many autoimmune diseases and can eventually provide an understanding that has been missed from genetics alone. This review will focus on the most commonly studied epigenetic modifications already demonstrated in PBC; special attention will be paid also to other epigenetic mechanisms so far not demonstrated in PBC patients, but that could increase our understanding in PBC pathogenesis.

10% liquid human immunoglobulin (KIOVIG®) for immunomodulation in autoimmune disorders

Intravenous immunoglobulins have been used to treat autoimmune disorders (ADs) for over 50 years. The etiologies of various ADs are not fully understood and although intravenous immunoglobulin treatment has proved its immunomodulatory properties, the roles of proposed mechanisms of action also remain a matter of speculation. A systemic search of the literature regarding KIOVIG® (Baxalta US, Inc., MA, USA) use in clinical trials on patients with ADs and a detailed review of retrieved articles revealed eight relevant publications. These articles reported KIOVIG use in multifocal motor neuropathy, chronic inflammatory demyelinating polyneuropathy, idiopathic thrombocytopenic purpura, Kawasaki disease, Guillain–Barré syndrome and other autoimmune and neurologic disorders and showed that KIOVIG is an effective, safe and well-tolerated treatment in the studied populations. Nevertheless, further studies on larger patient cohorts are needed.

The Autoimmune Ecology

Autoimmune diseases (ADs) represent a heterogeneous group of disorders that affect specific target organs or multiple organ systems. These conditions share common immunopathogenic mechanisms (i.e., the autoimmune tautology), which explain the clinical similarities they have among them as well as their familial clustering (i.e., coaggregation). As part of the autoimmune tautology, the influence of environmental exposure on the risk of developing ADs is paramount (i.e., the autoimmune ecology). In fact, environment, more than genetics, shapes immune system. Autoimmune ecology is akin to exposome, that is all the exposures - internal and external - across the lifespan, interacting with hereditary factors (both genetics and epigenetics) to favor or protect against autoimmunity and its outcomes. Herein, we provide an overview of the autoimmune ecology, focusing on the immune response to environmental agents in general, and microbiota, cigarette smoking, alcohol and coffee consumption, socioeconomic status (SES), gender and sex hormones, vitamin D, organic solvents, and vaccines in particular. Inclusion of the autoimmune ecology in disease etiology and health will improve the way personalized medicine is currently conceived and applied.

Infectomics and autoinfectomics: a tool to study infectious-induced autoimmunity

The exposome represents all exogenous and endogenous environmental exposures that begin at preconception and carry on throughout life, while the microbiome reflects the microbial component of the exposome. We recently introduced the concept of infectome and autoinfectome as a means of studying the totality of infections throughout life that participate in the induction as well as the progression of autoimmune diseases in an affected individual. The investigation of the autoinfectome could help us understand why some patients develop more than one autoimmune disease, a phenomenon also known as mosaic of autoimmunity. It could also explain the infectious and autoantibody burden of various autoimmune rheumatic diseases. The close interplay between infections and the immune system should be studied over time, long before the onset of autoaggression and autoimmunity. Tracking down each individual's exposure to infectious agents (as defined by the autoinfectome) would be important for the establishment of a causative link between infection and autoimmunity.

The challenge of treating orphan disease

Uncommon or orphan diseases are less frequently addressed in mainstream medical journals and, as a consequence, their understanding and clinical recognition may rely on case series or anecdotal data with limited guidelines and management directions. The study of selected underrepresented autoimmune and allergy conditions is the subject of the present issue of Clinical Reviews in Allergy and Immunology to provide peculiar perspectives on common and rare themes. First, allergy remains a major concern for physicians worldwide despite the limited developments over the past years, particularly for antigens such as mite or Alternaria alternata, and due to the increasing incidence of drug hypersensitivity. Second, the female predominance of autoimmune diseases such as systemic sclerosis is well recognized but enigmatic, and a unifying hypothesis remains elusive. Third, the management of conditions triggered by infectious agents as in Guillain-Barre syndrome or mixed cryoglobulinemia is challenging, and clinical guidelines are needed in the setting of infections and autoimmunity. Fourth, gamma-delta T cells represent major players in innate immunity and are the subject of extensive studies in autoimmune diseases to provide new therapeutic targets for disease prevention or modulation in the near future. Ultimately, we acknowledge the major developments in the broad fields of rheumatology and immunology and expect that microbiota definition, epigenetics studies, and microRNA analysis will provide new exciting avenues toward the understanding and treatment of chronic and acute inflammation.

Ins and outs of Helicobacter pylori association with autoimmune rheumatic diseases

Helicobacter pylori (H. pylori) infection is widely prevalent throughout worldwide. H. pylori manage a long-term survival in hostile environment of human stomach leading to peptic ulcer diseases and gastric cancer. But mostly infected person remains asymptomatic. Its chronic interaction with immune system makes H. pylori as an attractive candidate for the researchers to study its association with autoimmune diseases. This article presents a review of the literature on the association of H. pylori infection in selective autoimmune rheumatic diseases (RD). The authors used MeSH terms “Helicobacter pylori” with “rheumatoid arthritis,”“systemic lupus erythematosus,” or “fibromyalgia” to search PubMed database. All relevant studies identified were included. Despite extensive medical advancement many questions on role of H. pylori infection in autoimmune RD still remain unanswered. Further studies are therefore needed to address the role of H. pylori in pathogenesis of RD.

The mechanisms and applications of T cell vaccination for autoimmune diseases: a comprehensive review

Autoimmune diseases (ADs) are a spectrum of diseases originating from loss of immunologic self-tolerance and T cell abnormal autoreactivity, causing organ damage and death. However, the pathogenic mechanism of ADs remains unclear. The current treatments of ADs include nonsteroidal anti-inflammatory drugs (NSAIDS), antimalarials, corticosteroids, immunosuppressive drugs, and biological therapies. With the need to prevent side effects resulting from current treatments and acquire better clinical remission, developing a novel pharmaceutical treatment is extremely urgent. The concept of T cell vaccination (TCV) has been raised as the finding that immunization with attenuated autoreactive T cells is capable of inducing T cell-dependent inhibition of autoimmune responses. TCV may act as an approach to control unwanted adaptive immune response through eliminating the autoreactive T cells. Over the past decades, the effect of TCV has been justified in several animal models of autoimmune diseases including experimental autoimmune encephalomyelitis (EAE), murine autoimmune diabetes in nonobese diabetic (NOD) mice, collagen-induced arthritis (CIA), and so on. Meanwhile, clinical trials of TCV have confirmed the safety and efficacy in corresponding autoimmune diseases ranging from multiple sclerosis (MS) to systemic lupus erythematosus (SLE). This review aims to summarize the ongoing experimental and clinical trials and elucidate possible molecule mechanisms of TCV.

Ongoing activation of autoantigen-specific B cells in primary biliary cirrhosis

The serologic hallmark of primary biliary cirrhosis (PBC), the antimitochondrial response to the E2 component of the pyruvate dehydrogenase complex (PDC-E2), has unique features, including continuous high titers of immunoglobulin M (IgM) and IgG reactivity throughout all stages of disease, capable not only of target enzyme inhibition, but also crossreactive with chemical xenobiotics that share molecular homology with the inner lipoyl domain of PDC-E2; such chemicals have been proposed as potential etiological agents. We used flow cytometry and enzyme-linked immunospot assay (ELISPOT) to examine B-cell subsets in 59 subjects, including 28 with PBC, 13 with primary sclerosing cholangitis (PSC), and 18 healthy controls. Strikingly, in PBC, although there were no significant differences in B-cell phenotype subpopulations, 10% of the total IgG and IgA plasmablast population and 23% of the IgM plasmablast population were uniquely reactive with PDC-E2, detected in the CXCR7+ CCR10low plasmablast population. In contrast, plasmablast reactivity to a control antigen, tetanus toxoid, was minimal and similar in all groups. Additionally, we isolated plasmablast-derived polyclonal antibodies and compared reactivity with plasma-derived antibodies and noted a distinct noncirculating tissue source of xenobiotic crossreacting antibodies. The high levels of autoantigen specific peripheral plasmablasts indicate recent activation of naive or memory B cells and a continuous and robust activation. The presence of CXCR7+ CCR10low PDC-E2-specific ASCs suggests a mechanistic basis for the migration of circulating antigen specific plasmablasts to the mucosal epithelial ligands CXCL12 and CCL28.

CONCLUSION

Our findings suggest a sustained rigorous B-cell response in PBC, likely activated and perpetuated by cognate autoantigen.

Lactose inhibits regulatory T-cell-mediated suppression of effector T-cell interferon-γ and IL-17 production

Our interest in lactose as an immunomodulatory molecule results from studies showing that lactose binds to galectin-9, which has been shown to have various regulatory functions in the immune system including regulation of T-cell responses. Impaired regulation of T helper (Th)1 and Th17 type immune responses and dysfunction of regulatory T cells (T_reg) have been implicated in many human immune-mediated diseases. In the present study, we investigated the effects of lactose on immune regulation using co-cultures of human peripheral blood mononuclear cell (PBMC)-derived T_reg and effector T cells (T_eff) obtained from twenty healthy adults. T_reg, i.e. CD4⁺CD25⁺CD127⁻, were isolated from PBMC by immunomagnetic separation. The fraction of CD4⁺CD127⁻ cells that was depleted of CD25⁺ cells was used as T_eff. T_reg and T_eff at a ratio 1:5 were activated and the effects of lactose on the secretion of interferon-γ (IFN-γ) and IL-17 were analysed using ELISA for protein and quantitative RT-PCR for mRNA. T_reg down-regulated the secretion of both IFN-γ (8·8–3·9 ng/ml, n 20, P= 0·003) and IL-17 (0·83–0·64 ng/ml, n 15, P= 0·04) in co-cultures, while in the presence of lactose the levels of secreted IFN-γ and IL-17 remained high and no down-regulation was observed (16·4 v. 3·99 ng/ml, n 20, P< 0·0001, and 0·74 v. 0·64 ng/ml, n 15, P= 0·005, respectively). We showed that lactose inhibits human T_reg-mediated suppression of Th1 and Th17 immune responses in vitro.

Autoimmunity in 2012

The initiation and perpetuation of autoimmunity recognize numerous checkpoints, from the genomic susceptibility to the breakdown of tolerance. This latter phenomenon includes the loss of B cell anergy and T regulatory cell failure, as well as the production of autoantibodies and autoreactive T cells. These mechanisms ultimately lead to tissue injury via different mechanisms that span from the production of proinflammatory cytokines to the chemotaxis of immune cells to the target sites. The pathways to autoimmunity have been widely investigated over the past year and resulted in a number of articles in peer-reviewed journals that has increased by nearly 10 % compared to 2011. We herein follow on the attempt to provide a brief discussion of the majority of articles on autoimmune diseases that were published in the major immunology journals in the previous solar year. The selection is necessarily arbitrary and may thus not be seen as comprehensive but reflects current research trends. Indeed, 2012 articles were mostly dedicated to define new and old mechanisms with potential therapeutic implications in autoimmunity in general, though based on specific clinical conditions or animal models. As paradigmatic examples, the environmental influence on autoimmunity, Th17 changes modulating the autoimmune response, serum autoantibodies and B cell changes as biomarkers and therapeutic targets were major issues addressed by experimental articles in 2012. Further, a growing number of studies investigated the sex bias of autoimmunity and supported different working hypotheses to explain the female predominance, including sex chromosome changes and reproductive life factors. In conclusion, the resulting scenario illustrates that common factors may underlie different autoimmune diseases and this is well represented by the observed alterations in interferon-α and TGFβ or by the shared signaling pathways.

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.

Helicobacter pylori and autoimmune disease: Cause or bystander

Helicobacter pylori (H. pylori) is the main cause of chronic gastritis and a major risk factor for gastric cancer. This pathogen has also been considered a potential trigger of gastric autoimmunity, and in particular of autoimmune gastritis. However, a considerable number of reports have attempted to link H. pylori infection with the development of extra-gastrointestinal autoimmune disorders, affecting organs not immediately relevant to the stomach. This review discusses the current evidence in support or against the role of H. pylori as a potential trigger of autoimmune rheumatic and skin diseases, as well as organ specific autoimmune diseases. We discuss epidemiological, serological, immunological and experimental evidence associating this pathogen with autoimmune diseases. Although over one hundred autoimmune diseases have been investigated in relation to H. pylori, we discuss a select number of papers with a larger literature base, and include Sjögrens syndrome, rheumatoid arthritis, systemic lupus erythematosus, vasculitides, autoimmune skin conditions, idiopathic thrombocytopenic purpura, autoimmune thyroid disease, multiple sclerosis, neuromyelitis optica and autoimmune liver diseases. Specific mention is given to those studies reporting an association of anti-H. pylori antibodies with the presence of autoimmune disease-specific clinical parameters, as well as those failing to find such associations. We also provide helpful hints for future research.

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 does not increase the risk of UTIs following diagnosis compared to other chronic liver diseases?

BACKGROUND

Urinary Tract Infections (UTIs) occur more frequently in patients with Primary Biliary Cirrhosis (PBC). Previous studies have compared UTI occurrence in PBC and general population controls, however, it remains unclear if UTI is a feature of all chronic liver diseases (CLD)s, or is specific to PBC, or if this is a cause or consequence of PBC.

AIMS

We aimed to determine if UTIs are more common after a diagnosis of PBC compared to general population and CLD controls.

METHODS

A cohort study was conducted using the General Practice Research Database. We selected all cases of PBC plus 10 age- and sex-matched general population controls, and an unmatched group with other CLDs. We formed a Cox-proportional hazard model of time to first UTI following diagnosis.

RESULTS

Two hundred and forty-eight (24.6%) of PBC cases had a UTI event compared with 2127 (21.1%) of matched and 2131 (11.7%) of the unmatched CLD controls. Comparing PBC with matched controls showed an approximately 30% increased risk of UTI [hazard ratio (HR) 1.33 confidence interval (CI) 1.17-1.52]. Adjusting for diabetes, smoking and previous UTI reduced this (HR 1.25 CI 1.09-1.42). The Hazard Ratio comparing PBC with unmatched CLD controls was 2.00 (CI 1.76-2.28), but this became non-significant when adjusting for age, sex, diabetes, smoking and previous UTI 0.98 (0.86-1.12).

CONCLUSIONS

There is increased risk of UTI in PBC patients compared to general population controls, but not compared to CLD controls suggesting that this association is not specific to PBC after diagnosis.

Potential Roles for Infectious Agents in the Pathophysiology of Primary Biliary Cirrhosis: What's New?

Primary biliary cirrhosis (PBC) is a progressive cholestatic liver disease serologically characterized by the presence of high-titer antimitochondrial antibodies and, histologically by chronic nonsuppurative cholangitis and granulomata. The aetiology of the disease remains elusive, although genetic, epigenetic, environmental, and infectious factors have been considered important for the induction of the disease in genetically prone individuals. The disease shows a striking female predominance and becomes clinically overt at the fourth to sixth decade. These characteristics have prompted investigators to consider infections that predominate in women at these ages as the likely candidates for triggering the disease. Recurrent urinary tract infections due to Escherichia coli were the first infections to be considered pathogenetically relevant. Over the years, several other microorganisms have been linked to the pathogenesis of PBC owing to epidemiological, immunological, microbiological, or experimental findings in animal models. Recent studies have provided data supporting the pathogenic role of Novosphingobium aromaticivorans and betaretroviruses. Several reports have linked other organisms to the induction of the disease and/or the maintenance of the auto-aggressive responses that are perpetuated over the course of the disease. This review highlights the findings of the most recent studies investigating the link between infections and PBC. We also discuss the close interplay of the infectious agents with other environmental and genetic factors, which may explain the multifaceted nature of this puzzling disease.

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.

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.

p38 mitogen-activated protein kinase (p38 MAPK)-mediated autoimmunity: lessons to learn from ANCA vasculitis and pemphigus vulgaris

Evidence is beginning to accumulate that p38 mitogen activated protein kinase (p38 MAPK) signaling pathway plays an important role in the regulation of cellular and humoral autoimmune responses. The exact mechanisms and the degree by which the p38 MAPK pathway participates in the immune-mediated induction of diseases have started to emerge. This review discusses the recent advances in the molecular dissection of the p38 MAPK pathway and the findings generated by reports investigating its role in the pathogenesis of autoimmune diseases such as rheumatoid arthritis, systemic lupus erythematosus, and autoimmune hepatitis. Application of newly-developed protocols based on sensitive flow cytometric detection has proven to be a useful tool in the investigation of the phosphorylation of p38 MAPK within different peripheral blood mononuclear cell populations and may help us to better understand the enigmatic role of this signaling cascade in the induction of autoimmunity as well as its role in immunosuppressive-induced remission. Special attention is paid to reported data proposing a specific role for autoantibody-induced activation of p38 MAPK-mediated immunopathology in the pathogenesis of autoimmune blistering diseases and anti-neutrophilic antibody-mediated vasculitides.

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.

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.

Cutting-edge issues in autoimmunity and allergy of the digestive system

Autoimmunity and allergy involving the digestive system may be considered as paradigmatic for numerous common themes of complex diseases secondary to tolerance breakdown. Among gastrointestinal autoimmune diseases, for example, we encounter diseases in which a clear environmental trigger is identified (i.e., celiac disease), serum autoantibodies are most specific (i.e., primary biliary cirrhosis), or in which the disease pathophysiology is clearly understood (i.e., autoimmune gastritis). Similarly, it is intriguing that the gastrointestinal tract and the liver circulation represent the crucial environment for the development of immune tolerance. This issue is dedicated to the discussion of recent concepts while identifying two major common issues, i.e., the need for serum biomarkers and the role of vitamin D. Other common themes characterize the etiology and effector mechanisms of these and other autoimmune diseases and are discussed in each cutting-edge overview.

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.

Autoantibodies in autoimmune pancreatitis

Autoimmune pancreatitis (AIP) was first used to describe cases of pancreatitis with narrowing of the pancreatic duct, enlargement of the pancreas, hyper-γ-globulinaemia, and antinuclear antibody (ANA) positivity serologically. The main differential diagnosis, is pancreatic cancer, which can be ruled out through radiological, serological, and histological investigations. The targets of ANA in patients with autoimmune pancreatitis do not appear to be similar to those found in other rheumatological diseases, as dsDNA, SS-A, and SS-B are not frequently recognized by AIP-related ANA. Other disease-specific autoantibodies, such as, antimitochondrial, antineutrophil cytoplasmic antibodies or diabetes-specific autoantibodies are virtually absent. Further studies have focused on the identification of pancreas-specific autoantigens and reported significant reactivity to lactoferrin, carbonic anhydrase, pancreas secretory trypsin inhibitor, amylase-alpha, heat-shock protein, and plasminogen-binding protein. This paper discusses the findings of these investigations and their relevance to the diagnosis, management, and pathogenesis of autoimmune pancreatitis.

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.

Autoimmunity in Rheumatic Diseases Is Induced by Microbial Infections via Crossreactivity or Molecular Mimicry

A general consensus supports fundamental roles for both genetic and environmental, mainly microbial, factors in the development of autoimmune diseases. One form of autoimmune rheumatic diseases is confined to a group of nonpyogenic conditions which are usually preceded by or associated with either explicit or occult infections. A previous history of clinical pharyngitis, gastroenteritis/urethritis, or tick-borne skin manifestation can be obtained from patients with rheumatic fever, reactive arthritis, or Lyme disease, respectively, whilst, other rheumatic diseases like rheumatoid arthritis (RA), ankylosing spondylitis (AS), and Crohn's disease (CD) are usually lacking such an association with a noticeable microbial infection. A great amount of data supports the notion that RA is most likely caused by Proteus asymptomatic urinary tract infections, whilst AS and CD are caused by subclinical bowel infections with Klebsiella microbes. Molecular mimicry is the main pathogenetic mechanism that can explain these forms of microbe-disease associations, where the causative microbes can initiate the disease with consequent productions of antibacterial and crossreactive autoantibodies which have a great impact in the propagation and the development of these diseases.

Cutting-edge issues in organ-specific autoimmunity

There have been numerous methods and ways to classify autoimmune diseases. By far, the most traditional has been to separate immune-mediated pathology into organ-specific and organ-non-specific diseases. The classic systemic autoimmune diseases are, of course, rheumatoid arthritis and systemic lupus. The classic organ-specific autoimmune diseases have been autoimmune thyroiditis and autoimmune gastritis. However, as our understanding of the loss of tolerance has expanded, so has the long list of autoimmune diseases. In many cases, the distinction between organ-specific and organ-non-specific or systemic autoimmunity becomes a blur. In this issue, we discuss recent concepts in autoimmune pancreatitis, primary sclerosing cholangitis, Goodpasture's syndrome, myofasciitis, type I diabetes, polymyositis, autoimmune thyroid disease, IgA nephropathy, autoimmune uveitis, and ANCA-associated vasculitis. Common themes on both etiology and effector mechanisms are described throughout these papers with an attempt to provide a cutting-edge overview.

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.

Tuberculosis Is Not a Risk Factor for Primary Biliary Cirrhosis: A Review of the Literature

Primary biliary cirrhosis (PBC) is a progressive cholestatic liver disease characterised serologically by cholestasis and the presence of high-titre antimitochondrial antibodies, and histologically by chronic nonsuppurative cholangitis and granulomata. As PBC is a granulomatous disease andMycobacterium tuberculosisis the most frequent cause of granulomata, a causal relation between tuberculosis and PBC has been suggested. Attempts to find serological evidence of PBC-specific autoantibodies such as AMA have been made and, conversely, granulomatous livers from patients with PBC have been investigated for molecular evidence ofMycobacterium tuberculosis. This paper discusses in detail the reported data in support or against an association betweenMycobacterium tuberculosisinfection and PBC. We discuss the immunological and microbiological data exploring the association of PBC with exposure toMycobacterium tuberculosis. We also discuss the findings of large epidemiologic studies investigating the association of PBC with preexistent or concomitant disorders and the relevance of these findings with tuberculosis. Genome-wide association studies in patients with tuberculosis as well as in patients with PBC provide conclusive hints regarding the assumed association between exposure to this mycobacterium and the induction of PBC. Analysis of these data suggest thatMycobacterium tuberculosisis an unlikely infectious trigger of PBC.

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.

Immunopathogenesis of primary biliary cirrhosis: an old wives' tale

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

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.

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

Background

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

Methods

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

Results

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

Conclusions

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

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.