DNA typing of HLA class II genes; DRB1*0803 increases the susceptibility of Japanese to primary biliary cirrhosis

Investigational farnesoid X receptor agonists for the treatment of primary biliary cholangitis

INTRODUCTION

Up to 40% of Primary biliary cholangitis (PBC) patients have a suboptimal response to Ursodeoxycholic acid (UDCA). Close to half of such patients show a remarkable improvement when additionally treated with Obeticholic acid (OCA) but have a dose-dependent increase of pruritus. This relative success of OCA, a first-in-class Farnesoid receptor (FXR) agonist, has positioned FXR as an attractive target for drug development. Novel candidates have since emerged, providing hope for this subgroup of patients who lack effective and safe treatments.

AREAS COVERED

We discussed the role of bile acids in PBC pathogenesis and how the FXR agonists provide therapeutic value by affecting bile acid synthesis and transport. Novel FXR agonists undergoing pre-clinical and clinical trials for PBC were enlisted via literature search by including the terms 'FXR agonists,' 'FXR PBC,' 'PBC clinical trials' on PubMed, MEDLINE via Ovid, and Clinicaltrials.gov.

EXPERT OPINION

Novel FXR agonists currently under investigation for PBC improve the disease surrogate markers in early trials. However, as with OCA, pruritus remains a concern with the newer drugs despite targeted chemical modifications to increase FXR specificity. Directing future resources toward studying the molecular mechanisms behind pruritus may lead to better drug design and efficacious yet safer drugs.

Novel HLA allele associations with susceptibility, staging, symptomatic state, autoimmune hepatitis and hepatocellular carcinoma events for primary biliary cholangitis in the Japanese population

Primary biliary cholangitis (PBC) is a rare autoimmune disease with a clear predisposition for human leukocyte antigen (HLA)-DR/DQ-associated loss of immune tolerance for the E2 component of the pyruvate dehydrogenase complex. Three-field-resolution HLA imputation of 1,670 Japanese PBC patients and 2,328 healthy controls was conducted using Japanese population-specific HLA reference panels. Eighteen previously reported Japanese PBC-associated HLA alleles were confirmed and extended to 3-field-resolution, including HLA-DRB1*08:03 to HLA-DRB1*08:03:02, HLA-DQB1*03:01 to HLA-DQB1*03:01:01, HLA-DQB1*04:01 to HLA-DQB1*04:01:01 and HLA-DQB1*06:04 to HLA-DQB1*06:04:01. In addition, additional significant novel HLA alleles were identified, including 3 novel susceptible HLA-DQA1 alleles: HLA-DQA1*03:03:01, HLA-DQA1*04:01:01, HLA-DQA1*01:04:01 and 1 novel protective HLA-DQA1 allele, HLA-DQA1*05:05:01. In addition, PBC patients carrying HLA-DRB1*15:01:01 and HLA-DQA1*03:03:01 would have a higher predisposition toward developing concomitant autoimmune hepatitis (AIH). Further, late-stage and symptomatic PBC shared the same susceptible HLA alleles of HLA-A*26:01:01, HLA-DRB1*09:01:02 and HLA-DQB1*03:03:02. Lastly, HLA-DPB1*05:01:01 was identified as a potential risk HLA allele for development of hepatocellular carcinoma (HCC) in PBC patients. In conclusion, we have extended the current knowledge of HLA allele associations to 3-field resolution and identified novel HLA allele associations with predisposition risk, staging, symptomatic state, and AIH and HCC events for Japanese PBC patients.

Mechanism-based target therapy in primary biliary cholangitis: opportunities before liver cirrhosis?

Primary biliary cholangitis (PBC) is an immune-mediated liver disease characterized by cholestasis, biliary injuries, liver fibrosis, and chronic non-suppurative cholangitis. The pathogenesis of PBC is multifactorial and involves immune dysregulation, abnormal bile metabolism, and progressive fibrosis, ultimately leading to cirrhosis and liver failure. Ursodeoxycholic acid (UDCA) and obeticholic acid (OCA) are currently used as first- and second-line treatments, respectively. However, many patients do not respond adequately to UDCA, and the long-term effects of these drugs are limited. Recent research has advanced our understanding the mechanisms of pathogenesis in PBC and greatly facilitated development of novel drugs to target mechanistic checkpoints. Animal studies and clinical trials of pipeline drugs have yielded promising results in slowing disease progression. Targeting immune mediated pathogenesis and anti-inflammatory therapies are focused on the early stage, while anti-cholestatic and anti-fibrotic therapies are emphasized in the late stage of disease, which is characterized by fibrosis and cirrhosis development. Nonetheless, it is worth noting that currently, there exists a dearth of therapeutic options that can effectively impede the progression of the disease to its terminal stages. Hence, there is an urgent need for further research aimed at investigating the underlying pathophysiology mechanisms with potential therapeutic effects. This review highlights our current knowledge of the underlying immunological and cellular mechanisms of pathogenesis in PBC. Further, we also address current mechanism-based target therapies for PBC and potential therapeutic strategies to improve the efficacy of existing treatments.

New insights on the role of human leukocyte antigen complex in primary biliary cholangitis

Primary Biliary Cholangitis (PBC) is a rare autoimmune cholangiopathy. Genetic studies have shown that the strongest statistical association with PBC has been mapped in the human leukocyte antigen (HLA) locus, a highly polymorphic area that mostly contribute to the genetic variance of the disease. Furthermore, PBC presents high variability throughout different population groups, which may explain the different geoepidemiology of the disease. A major role in defining HLA genetic contribution has been given by genome-wide association studies (GWAS) studies; more recently, new technologies have been developed to allow a deeper understanding. The study of the altered peptides transcribed by genetic alterations also allowed the development of novel therapeutic strategies in the context of immunotolerance. This review summarizes what is known about the immunogenetics of PBC with a focus on the HLA locus, the different distribution of HLA alleles worldwide, and how HLA modifications are associated with the pathogenesis of PBC. Novel therapeutic strategies are also outlined.

HLA, gut microbiome and hepatic autoimmunity

Genetic susceptibility to autoimmune liver diseases is conferred mainly by polymorphisms of genes encoding for the human leukocyte antigens (HLA). The strongest predisposition to autoimmune hepatitis type 1 (AIH-1) is linked to the allele DRB1*03:01, possession of which is associated with earlier disease onset and more severe course. In populations where this allele is very rare, such as in Asia, and in DRB1*03-negative patients, risk of AIH-1 is conferred by DRB1*04, which is associated with later disease onset and milder phenotype. AIH type 2 (AIH-2) is associated with DRB1*07. The pediatric condition referred to as autoimmune sclerosing cholangitis (ASC), is associated with the DRB1*13 in populations of Northern European ancestry. DRB1*1501 is protective from AIH-1, AIH-2 and ASC in Northern European populations. Possession of the DRB1*08 allele is associated with an increased risk of primary biliary cholangitis (PBC) across different populations. DRB1*03:01 and B*08:01 confer susceptibility to primary sclerosing cholangitis (PSC), as well as DRB1*13 and DRB1*15 in Europe. The hepatic blood supply is largely derived from the splanchnic circulation, suggesting a pathophysiological role of the gut microbiome. AIH appears to be associated with dysbiosis, increased gut permeability, and translocation of intestinal microbial products into the circulation; molecular mimicry between microbial and host antigens may trigger an autoaggressive response in genetically-predisposed individuals. In PBC an altered enteric microbiome may affect intestinal motility, immunological function and bile secretion. Patients with PSC have a gut microbial profile different from health as well as from patients with inflammatory bowel disease without PSC.

A case of methimazole-induced acute pancreatitis with an HLA allele causing antithyroid drug-induced agranulocytosis

Among the side effects of methimazole (MMI) for the treatment of Graves’ disease, MMI-induced acute pancreatitis (MIP) is a rare adverse reaction, with only 7 cases being reported to date. However, 2 large-scale population-based studies recently revealed that the risk of MIP was significantly higher, ranging from 0.02% to 0.56%. Although MIP is common in middle-aged and elderly Asian women, its pathogenesis remains largely unknown. We herein present a case of a 72-year-old Japanese woman with Graves’ disease who developed MIP 12 days after the initiation of MMI. The MMI was discontinued, the patient was switched to propylthiouracil (PTU) therapy, and pancreatitis gradually resolved. Serological human leukocyte antigen (HLA) typing identified HLA-DRB1*08:03:02. This HLA allele was previously detected in a patient with MIP and is one of the major risk factors for agranulocytosis induced by antithyroid drugs, including PTU as well as MMI. In cases of MIP, PTU is being considered as an alternative to MMI; however, its safety needs further investigation and patients require close monitoring after the switch to PTU. Further studies are warranted, particularly on the relationship between MIP and the presence of HLA alleles causing antithyroid drug-induced agranulocytosis.

MicroRNAs in autoimmune liver diseases: from diagnosis to potential therapeutic targets

Autoimmune liver diseases (AILDs) are a group of liver disorders composed of autoimmune hepatitis (AIH), primary biliary cholangitis (PBC), and primary sclerosing cholangitis (PSC) characterized by chronic hepatic and biliary inflammation. Although several genetic factors, such as HLA alleles, TNFA, and CTLA-4, have been reported in the pathogenesis of AILDs, many details remain unknown. In recent years, microRNAs (miRNAs) have emerged as crucial components in the diagnosis and therapeutic applications of various autoimmune diseases, including systemic lupus erythematosus (SLE), glomerulonephritis, and AILDs. MiRNAs comprise a class of small, noncoding molecules of 19--25 nucleotides that modulate multiple genes by suppressing or degrading target mRNAs. Altered miRNA profiles have been identified in serum, immune cells, and live tissues from AILD patients. Elevated serum miR-21 and miR-122 levels in AIH patients as well as decreased miR-200c levels in PSC patients indicate their diagnostic utility. Highly expressed miR-122 and miR-378f as well as downregulated miR-4311 and miR-4714-3p in serum samples from refractory PBC patients suggest their potential to evaluate treatment efficacy. Moreover, miRNAs have been reported to participate in AILD development. Increased miR-506 levels may impair bile secretion in PBC by inhibiting Cl-/HCO3-anion exchanger 2 (AE2) and type III inositol 1,4,5-trisphosphate receptor-3 (InsP3R3). Additionally, different miRNA mimics or antagonists, such as atagomiR-155 and miR-223 mimics, have been widely applied in experimental AILD murine models with great efficacy. Here, we provide an overview of miRNAs in AILDs, aiming to summarize their potential roles in diagnosis and therapeutic interventions, and we discuss the challenges and future applications of miRNAs in clinical practice.

Primary biliary cholangitis: pathogenesis and therapeutic opportunities

Primary biliary cholangitis is a chronic, seropositive and female-predominant inflammatory and cholestatic liver disease, which has a variable rate of progression towards biliary cirrhosis. Substantial progress has been made in patient risk stratification with the goal of personalized care, including early adoption of next-generation therapy with licensed use of obeticholic acid or off-label fibrate derivatives for those with insufficient benefit from ursodeoxycholic acid, the current first-line drug. The disease biology spans genetic risk, epigenetic changes, dysregulated mucosal immunity and altered biliary epithelial cell function, all of which interact and arise in the context of ill-defined environmental triggers. A current focus of research on nuclear receptor pathway modulation that specifically and potently improves biliary excretion, reduces inflammation and attenuates fibrosis is redefining therapy. Patients are benefiting from pharmacological agonists of farnesoid X receptor and peroxisome proliferator-activated receptors. Immunotherapy remains a challenge, with a lack of target definition, pleiotropic immune pathways and an interplay between hepatic immune responses and cholestasis, wherein bile acid-induced inflammation and fibrosis are dominant clinically. The management of patient symptoms, particularly pruritus, is a notable goal reflected in the development of rational therapy with apical sodium-dependent bile acid transporter inhibitors.

The genetics of primary biliary cholangitis

PURPOSE OF REVIEW

Primary biliary cholangitis (PBC) is a female predominant chronic autoimmune disease of the intrahepatic bile ducts and with a long latent period. It is crucial to understand how genetics contribute to the disease.

RECENT FINDINGS

Geo-epidemiological studies in PBC have provided evidence of familial risk; case-control studies and genome wide association studies have identified various human leukocyte antigen (HLA) and non-HLA alleles that are associated with PBC. However, these alleles are non-PBC specific and most of the identified non-HLA loci were also found to be susceptible genes in other autoimmune diseases and different between study populations.

SUMMARY

Patients with PBC are often asymptomatic and often left undiagnosed. There are no known HLA and non-HLA alleles specific for PBC. Global effort and novel approaches such as epigenetics directed at identification of genetic risk factors will greatly facilitate accurate and timely diagnosis, which will improve prognosis and increase treatment options.

The Genetics and Epigenetics of Primary Biliary Cholangitis

Both genetic background and environmental factors contribute to primary biliary cholangitis (PBC). Recent innovative technologies, such as genome-wide association studies, identified a remarkable number of susceptible nonhuman leukocyte antigen genes contributing to the development of PBC; however, they are primarily indicators of active immunologic responses commonly involved in autoimmune reactions. Thus, recent studies have focused on epigenetic mechanisms that would link genetic predisposition and environmental triggering factors. In PBC, methylation profiling and altered X chromosome architecture have been intensively explored in conjunction with a striking female predominance. Further, microRNAs have been found to be associated with the etiology of PBC.

Genetic and epigenetic influences on the loss of tolerance in autoimmunity

Immunological tolerance loss is fundamental to the development of autoimmunity; however, the underlying mechanisms remain elusive. Immune tolerance consists of central and peripheral tolerance. Central tolerance, which occurs in the thymus for T cells and bone marrow for B cells, is the primary way that the immune system discriminates self from non-self. Peripheral tolerance, which occurs in tissues and lymph nodes after lymphocyte maturation, controls self-reactive immune cells and prevents over-reactive immune responses to various environment factors. Loss of tolerance results in autoimmune disorders, such as systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), type 1 diabetes (T1D) and primary biliary cirrhosis (PBC). The etiology and pathogenesis of autoimmune diseases are highly complicated. Both genetic predisposition and epigenetic modifications are implicated in the loss of tolerance and autoimmunity. In this review, we will discuss the genetic and epigenetic influences on tolerance breakdown in autoimmunity. Genetic and epigenetic influences on autoimmune diseases, such as SLE, RA, T1D and PBC, will also be briefly discussed.

Pathophysiology of primary biliary cholangitis

Primary biliary cholangitis is a prototypical autoimmune disease characterized by an overwhelming female predominance, a distinct clinical phenotype, and disease specific anti-mitochondrial antibodies targeted against a well-defined auto-antigen. In a genetically susceptible host, multi-lineage loss of tolerance to the E2 component of the 2-oxo-dehydrogenase pathway and dysregulated immune pathways directed at biliary epithelial cells leads to cholestasis, progressive biliary fibrosis, and cirrhosis in a subset of patients. Several key insights have shed light on the complex pathogenesis of disease. First, characteristic anti-mitochondrial antibodies (AMAs) target lipoic acid containing immunodominant epitopes, particularly pyruvate dehydrogenase complex (PDC-E2), on the inner mitochondrial membrane of BECs. Next, breakdown of the protective apical bicarbonate rich umbrella may sensitize BECs to aberrant apoptotic pathways leaving the antigenic PDC-E2 epitope immunologically tact within an apoptotic bleb. A multi-lineage immune response ensues characterized by an imbalance between effector and regulatory activity resulting in progressive and self-perpetuating biliary injury. Genome wide studies shed light on important pathways involved in disease, key among them being IL-12. Epigenetic mechanisms and microRNAs may play help shed light on the missing heritability and female preponderance of disease. Taken together, these findings have dramatically advanced our understanding of disease and may lead to important therapeutic advances.

Geoepidemiology and (epi-)genetics in primary biliary cholangitis

Primary biliary cholangitis (PBC) is a rare female preponderant chronic autoimmune cholestatic liver disease, characterized by intrahepatic ductopenia and progressive fibrosis. During last decades incidence and prevalence showed an increasing rate which vary widely worldwide demonstrating an important interaction between environmental and genetic factors. Heritability suggested by familial occurrence and monozygotic twins concordance have been confirmed in more studies. Epigenetics mechanisms such as histone modification and DNA methylation can partially explain predisposition and inheritance of this disease. Nevertheless, an association with specific class II human leukocyte antigen (HLA) variants have been reported, showing an increase risk in susceptibility. More recently, data regarding a strong protective association between PBC and HLA alleles confirmed this association. After recent genome-wide association studies (GWAS), a more intricate interaction between PBC and the HLA region has been shown. Furthermore, GWAS also identified several immune-related-genes implicated. More genome-wide association studies on this disease are needed to reach a complete and systematic knowledge of this disease. In this review we discuss more recent issued data on geoepidemiology of PBC and the role of (epi-)genetic mechanisms in its pathogenesis.

Advances in understanding pathogenesis of primary biliary cholangitis

Primary biliary cholangitis (PBC) is an autoimmune liver disease characterized by chronic and progressive cholestasis. In recent years, the incidence and prevalence of PBC are increasing year by year. However, the etiology and pathogenesis are not fully understood. It is believed that genetic susceptibility, environmental factors, and immunologic tolerance are related with the pathogenesis of PBC. This article reviews the progress in the understanding of the pathogenesis of PBC.

Genome-Wide Association Studies in Primary Biliary Cirrhosis

Genome-wide association studies (GWASs) have been a significant technological advance in our ability to evaluate the genetic architecture of complex diseases such as primary biliary cirrhosis (PBC). To date, six large-scale studies have been performed that have identified 27 risk loci in addition to human leukocyte antigen (HLA) associated with PBC. The identified risk variants emphasize important disease concepts; namely, that disturbances in immunoregulatory pathways are important in the pathogenesis of PBC and that such perturbations are shared among a diverse number of autoimmune diseases-suggesting the risk architecture may confer a generalized propensity to autoimmunity not necessarily specific to PBC. Furthermore, the impact of non-HLA risk variants, particularly in genes involved with interleukin-12 signaling, and ethnic variation in conferring susceptibility to PBC have been highlighted. Although GWASs have been a critical stepping stone in understanding common genetic variation contributing to PBC, limitations pertaining to power, sample availability, and strong linkage disequilibrium across genes have left us with an incomplete understanding of the genetic underpinnings of disease pathogenesis. Future efforts to gain insight into this missing heritability, the genetic variation that contributes to important disease outcomes, and the functional consequences of associated variants will be critical if practical clinical translation is to be realized.

Primary biliary cirrhosis

Primary biliary cirrhosis is a chronic cholestatic liver disease characterised by destruction of small intrahepatic bile ducts, leading to fibrosis and potential cirrhosis through resulting complications. The serological hallmark of primary biliary cirrhosis is the antimitochondrial antibody, a highly disease-specific antibody identified in about 95% of patients with primary biliary cirrhosis. These patients usually have fatigue and pruritus, both of which occur independently of disease severity. The typical course of primary biliary cirrhosis has changed substantially with the introduöction of ursodeoxycholic acid (UDCA). Several randomised placebo-controlled studies have shown that UDCA improves transplant-free survival in primary biliary cirrhosis. However, about 40% of patients do not have a biochemical response to UDCA and would benefit from new therapies. Liver transplantation is a life-saving surgery with excellent outcomes for those with decompensated cirrhosis. Meanwhile, research on nuclear receptor hormones has led to the development of exciting new potential treatments. This Seminar will review the current understanding of the epidemiology, pathogenesis, and natural history of primary biliary cirrhosis, discuss management of the disease and its sequelae, and introduce research on new therapeutic options.

The accuracy of the anti-mitochondrial antibody and the M2 subtype test for diagnosis of primary biliary cirrhosis: a meta-analysis

The aim of this study was to evaluate the diagnostic value of anti-mitochondrial antibodies (AMAs) and/or the M2 subtype (AMA-M2) in patients with primary biliary cirrhosis (PBC). AMA/AMA-M2 data were obtained by searching electronic databases. Studies showing AMA/AMA-M2 results in patients with PBC and control groups with other liver diseases or healthy livers were included. The quality of the involved studies was assessed using the QUADAS tool. The pooled sensitivity and specificity were calculated, and stratified analysis was performed according to possible heterogeneity sources. The pooled AMA (all methods) sensitivity and specificity were 84.5% (95% confidence interval (CI) 83.3%-85.6%) and 97.8% (95% CI 97.6%-98.0%), respectively. The positive and negative likelihood ratios were 25.201 (95% CI 17.583-36.118) and 0.162 (95% CI 0.131-0.199), respectively. The current evidence suggests that AMA and AMA-M2 show favorable accuracy for the diagnosis of PBC with high specificity and sensitivity. AMA is a better and more comprehensive marker than AMA-M2. The accuracy established in this meta-analysis is based on clinical studies using patient cohorts from different ethnicities.

HLA-DR polymorphism and primary biliary cirrhosis: evidence from a meta-analysis

BACKGROUND AND AIMS

We undertook this study to review and quantitatively analyze the association between human leukocyte antigen (HLA) DR polymorphisms and susceptibility of primary biliary cirrhosis (PBC).

METHODS

All relevant publications on the association between HLA-DR polymorphisms and PBC were searched through June 2013. Odds ratios (OR) and confidence intervals (CI) for the comparisons between case and control group were calculated. Statistical analysis was performed using Stata 11.0 software.

RESULTS

Nineteen articles (or 20 studies including the substudies) were identified. For DR*7 allele, the ORs (95% CIs) were 1.530 (1.310, 1.788), 1.757 (1.285, 2.403) and 1.495 (1.211, 1.845) in overall, Asian and European populations, respectively. For DR*8 alleles, the ORs (95% CIs) were 3.158 (1.822, 5.475), 2.803 (2.420, 3.247) and 3.056 (2.573, 3.629) in Asian, American and European subgroups, respectively. The subgroup analysis for DR*11 and DR*13 showed a significant association in Asian and European population. For DR*12 and *15 alleles, the overall ORs (95% CIs) were 0.551 (0.404, 0.753) and 0.721 (0.607, 0.857). However, in subgroup analysis for DR*12 allele, the association was only found in Asian population. In addition, statistical significance exists in American and European populations in the subgroup analysis for DR*15 allele.

CONCLUSION

Our meta-analysis suggested that HLA-DR *7 and *8 allele polymorphisms contributed to the susceptibility of PBC, whereas DR*11, *12, *13 and *15 allele polymorphisms are protective factors in certain population.

Human leucocyte antigen alleles and haplotypes and their associations with antinuclear antibodies features in Chinese patients with primary biliary cirrhosis

BACKGROUND & AIMS

Primary biliary cirrhosis (PBC) is an autoimmune liver disease. Genetic factors are critical in determining susceptibility to PBC. Among human leuocyte antigen (HLA) genes, an association between the DRB1*08 allele and PBC has been reported in many populations, but not in Chinese patients.

METHODS

We investigated HLA-A, B, DRB1, and DQB1 alleles and haplotypes in 145 PBC patients and 500 healthy subjects. Patients were also stratified according to autoantibody features, and associations between these and HLA alleles were analyzed.

RESULTS

Significant associations existed between HLA-DRB1*08:03 (22.1% vs. 9.0%, Pc < 0.0001, OR = 2.86), DQ2 (41.4% vs. 25.4%, Pc < 0.0001, OR = 2.07) and DQB1*06:01 (31.0% vs. 17.8%, Pc = 0.014, OR = 2.08) alleles and PBC. DRB1*08:03-DQB1*06:01 (22.1% vs. 8.2%, P < 0.0001, OR = 3.17) and DRB1*07:01-DQB1*02:02 haplotypes (28.3% vs. 17.6%, P = 0.005, OR = 1.85) were also associated with PBC susceptibility. In contrast, the DQB1*03:01 allele (21.4% vs. 39.2%, Pc < 0.0001, OR = 0.42) and DRB1*12:02-DQB1*03:01 haplotype (6.9% vs. 14.6%, P = 0.015, OR = 0.43) were significantly decreased in PBC patients compared with controls. DRB1*14:54 and DQ5(1) protected against antinuclear antibody (ANA) (OR = 0.25) and anti-gp210 antibody (OR = 0.39) production, respectively, while HLA-B*44:03 predisposed patients to anti-gp210 antibody (OR = 5.70) production.

CONCLUSION

These results suggest that Chinese patients with PBC have a distinct genetic background in eastern Asia, and we confirmed the role of HLA genes in determining PBC susceptibility and autoantibody features in the Chinese population.

Association of human leukocyte antigen class II with susceptibility to primary biliary cirrhosis: a systematic review and meta-analysis

Purpose

Several previous studies suggested that HLA-ClassII may be associated with susceptibility to primary biliary cirrhosis (PBC), but data from individual studies remain controversial. Therefore, a systematic review and meta-analysis is needed to comprehensively evaluate the association between HLA-ClassII and PBC risk.

Methods

All published reports of an association between HLA class II and PBC risk were searched in PubMed, EMBASE (updated to 22 May 2012). ORs with 95% confidence intervals (CIs) were extracted from each included study and the meta-analysis was performed using the fixed- or random-effects model.

Results

A total of 3,732 PBC patients and 11,031 controls from 34 studies were included in the meta-analysis. An assessment of study quality revealed that the majority of studies included (18 studies) were of high quality. The serological group DR8 was found to be a risk factor for PBC (OR = 2.82, 95%CI: 1.84–4.30). At the allelic level, HLA-DR*08 and HLA-DR*0801 were identified as risk factors for PBC (OR = 2.30, 95%CI: 1.76-3.00; OR = 3.23, 95%CI: 2.22–4.70, respectively), whereas HLA-DR*11 and HLA-DR*13 were potent protective factors (OR = 0.31, 95%CI: 0.27-0.38; OR = 0.62, 95%CI: 0.48-0.81, respectively). HLA-DQB1 and HLA-DQB1*0402 conferred a predisposition to PBC development (OR = 3.47, 95%CI: 2.35–5.13), whereas HLA-DQB1*0604 was protective against PBC (OR = 0.3, 95%CI: 0.18–0.58). No HLA-DPB1 allele was observed to be associated with PBC susceptibility (P > 0.05).

Conclusions

The present study revealed that HLA-ClassII components are closely associated with the development of PBC.

Distinct microRNAs expression profile in primary biliary cirrhosis and evaluation of miR 505-3p and miR197-3p as novel biomarkers

BACKGROUND AND AIMS

MicroRNAs are small endogenous RNA molecules with specific expression patterns that can serve as biomarkers for numerous diseases. However, little is known about the expression profile of serum miRNAs in PBC.

METHODS

First, we employed Illumina deep sequencing for the initial screening to indicate the read numbers of miRNA expression in 10 PBC, 5 CH-C, 5 CH-B patients and 5 healthy controls. Comparing the differentially expressed miRNAs in the 4 groups, analysis of variance was performed on the number of sequence reads to evaluate the statistical significance. Hierarchical clustering was performed using an R platform and we have found candidates for specific miRNAs in the PBC patients. Second, a quantitative reverse transcription PCR validation study was conducted in 10 samples in each group. The expression levels of the selected miRNAs were presented as fold-changes (2(-ΔΔCt)). Finally, computer analysis was conducted to predict target genes and biological functions with MiRror 2.0 and DAVID v6.7.

RESULTS

We obtained about 12 million 32-mer short RNA reads on average per sample and the mapping rates to miRBase were 16.60% and 81.66% to hg19. In the statistical significance testing, the expression levels of 81 miRNAs were found to be differentially expressed in the 4 groups. The heat map and hierarchical clustering demonstrated that the miRNA profiles from PBC clustered with those of CH-B, CH-C and healthy controls. Additionally, the circulating levels of hsa-miR-505-3p, 197-3p, and 500a-3p were significantly decreased in PBC compared with healthy controls and the expression levels of hsa-miR-505-3p, 139-5p and 197-3p were significantly reduced compared with the viral hepatitis group.

CONCLUSIONS

Our results indicate that sera from patients with PBC have a unique miRNA expression profile and that the down-regulated expression of hsa-miR-505-3p and miR-197-3p can serve as clinical biomarkers of PBC.

Autoimmune hepatitis-primary biliary cirrhosis overlap syndrome concomitant with immune hemolytic anemia and immune thrombocytopenic purpura (Evans syndrome)

Autoimmune hepatitis (AIH) and primary biliary cirrhosis (PBC) associated with Evans syndrome; combination of autoimmune hemolytic anemia (AIHA) and immune thrombocytopenic purpura (ITP) has rarely been reported. We report the case of a 53-year-old patient who presented with weakness, myalgia, arthralgia, shortness of breath and purpura. Initial laboratory investigations revealed liver dysfunction, anemia and thrombocytopenia. Anti-nuclear (ANA) and antimitochondrial M2 (AMA M2) antibodies were positive. Diagnose of PBC-AIH overlap was made by clinical, serological and histological investigations. AIHA and ITP was identified with clinical-laboratory findings and bone marrow puncture. She was treated with IVIG followed by prednisolone and ursodeoxycholic acid. Hemoglobin-thrombocytes increased rapidly and transaminases improved at day 8. We have reported the first case in the literature with AIH-PBC overlap syndrome concurrent by ITP and AIHA which suggest the presence of shared genetic susceptibility factors in multiple autoimmune conditions including AIH, PBC, ITP and AIHA.

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

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

Primary biliary cirrhosis and liver transplantation

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

Etiopathogenesis of primary biliary cirrhosis: an overview of recent developments

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

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

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

CONCLUSION

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

Complete spectrum of AMA-M2 positive liver disease in north India

PURPOSE

This study describes the clinical, histological, and genetic profile of AMA-M2 positive liver disease in north India.

METHODS

Over 13.5 years, 11,221 patients suspected of AiLD (autoimmune liver disease) and negative for viral markers were screened for autoantibodies, ANA, ASMA, AMA, and LKM, by indirect immunofluorescence. Of these patients, 135 were AMA positive and 132 AMA-M2 positive. Clinical presentation of most of these patients was neither typical of AIH nor PBC. Sera of these patients were further tested for gp 210 and Sp 100. Fifty consecutive consenting patients were typed for HLA class II alleles DR and DQ and their clinical, biochemical, histology and genetic profiles were reviewed to characterize the disease spectrum in north India.

RESULTS

Only 22 of 50 patients had liver histology reports, and could be categorized on the basis of the criteria by Chazouillers et al. Of these 22, 13 had overlap syndrome, eight had classical PBC, whereas one had probable PBC. The remaining 28 could not be suitably categorized due to lack of liver histology. HLA DRB1*03 was found to be significantly associated with the disease in North Indian population.

CONCLUSION

This 13.5-year study demonstrates a definite rising annual incidence of AMA-M2-positive liver disease in north India. Complete evaluation of 50 patients indicated that a hepatitic variant of PBC (PBC-AIH), which is significantly associated with DRB1*03, predominates in north India.

Association between CTLA-4 exon-1 +49A>G polymorphism and primary biliary cirrhosis risk: a meta-analysis

BACKGROUND AND AIMS

CTLA-4 exon-1 +49A>G polymorphisms have been reported to influence the risk for primary biliary cirrhosis in many studies; however, the results still remain controversial and ambiguous. The aim of this study was to determine more precise estimations for the relationship between CTLA-4 exon-1 +49A>G polymorphisms and the risk for primary biliary cirrhosis.

METHODS

Electronic searches for all publications were conducted on associations between this variant and breast cancer in several databases through November 2010. Crude odds ratios (ORs) with 95% confidence intervals (CIs) were calculated to estimate the strength of the association. Eight studies were identified including 2151 cases and 2214 controls.

RESULTS

Overall, there were no significant associations between CTLA +49G>A polymorphism and primary biliary cirrhosis risk (codominant model: GA vs. AA OR=1.190, 95% CI=0.818-1.732; GG vs. AA OR=1.153, 95% CI=0.858-1.550; dominant model: OR=1.181, 95% CI=0.873-1.599; and recessive model: OR=1.148; 95% CI=0.903-1.459). In the subgroup analysis by ethnicity, a significantly increased risk was found for Asians (GG vs. AA OR=1.873; 95% CI=1.202-2.921) and recessive model (OR=1.758; 95% CI = 1.271-2.433). In the stratified analysis by control sources, significant association were observed in population-based studies (GA vs. AA OR=1.432; 95% CI=1.078-1.902).

CONCLUSIONS

This meta-analysis suggests that the CTLA-4 +49G>A polymorphism may be a risk factor for primary biliary cirrhosis in Asians.

Human leukocyte antigen in primary biliary cirrhosis: an old story now reviving

Primary biliary cirrhosis (PBC) is an autoimmune biliary disease characterized by injury of small and medium size bile ducts, eventually leading to liver cirrhosis and death. Although the causes remain enigmatic, recent evidence has strengthened the importance of genetic factors in determining the susceptibility to the disease. Besides the strong heritability suggested by familial occurrence and monozygotic twins concordance, for decades there has not been a clear association with specific genes, with the only exception of a low risk conferred by a class II human leukocyte antigen (HLA) variant, the DRB1*08 allele, at least in some populations. The picture has become more complete when strong protective associations between PBC and the HLA DRB1*11 and DRB1*13 alleles were found in Italian and UK series. However, HLA genes have begun again to attract interest thanks to recent genome-wide association studies (GWAS), which clearly demonstrated that the major components of the genetic architecture of PBC are within the HLA region. As expected in a genetically complex disease, GWAS also identified several novel non-HLA variants, but it is worth noting that all of them are in immuno-related genes. In this review, the paradigmatic tale of what, and how, we learned about HLA genes in PBC will be retraced with particular focus on how GWAS are enabling a rewriting the story of PBC pathogenesis. These recent discoveries will not only drive functional studies but will also hold the promise of developing novel disease-specific treatments.

Polymyositis associated with autoimmune hepatitis, primary biliary cirrhosis, and autoimmune thrombocytopenic purpura

We describe a 40-year-old woman with polymyositis (PM) who developed autoimmune hepatitis (AIH), primary biliary cirrhosis (PBC), and autoimmune thrombocytopenic purpura (AITP) concurrently. About 4 years earlier, she suffered from muscle weakness probably due to PM. When she visited our hospital, she had polyarthritis, myalgia, symmetrical proximal limb-muscle weakness, elevated muscle enzymes, and myogenic abnormalities on electromyogram. Pathological findings obtained by muscle biopsy showed histological findings consistent with PM. Her serum liver enzymes were also elevated. The histology obtained by liver biopsy revealed the mixture findings of chronic active hepatitis and biliary cirrhosis. As antibodies to mitochondria M2 and liver/kidney microsome type 1 (LKM-1) were present, we concluded her liver disease was due to an overlap of AIH and PBC. Furthermore, purpura on the legs with thrombocytopenia appeared in parallel with liver dysfunction. She was diagnosed as having AITP by clinical and laboratory findings. Her serum showed a speckled pattern in immunofluorescence antinuclear antibody testing, but the antigen specificities were distinct from those of the known myositis-related autoantigens. This is a first case report of PM accompanied by AIH, PBC, and AITP. It was notable that there was an overlap of disease-associated immunological findings and immunogenetic backgrounds. This case provides a possible insight into the mechanisms and interplay of autoimmune diseases.

Primary biliary cirrhosis

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

Familial clustering and genetic background of primary biliary cirrhosis in Japan

BACKGROUND

Primary biliary cirrhosis (PBC) is regarded as an autoimmune liver disease and familial clustering of PBC could represent some genetic predisposition to the disease.

AIMS

To elucidate the genetic background of PBC by investigating familial cases of PBC.

METHODS

Familial cases were picked out from 171 PBC patients who enrolled in this study. We analyzed them and their family members, and compared them clinically and immunogenetically to non-familial cases.

RESULTS

Out of 171 PBC patients, ten (5.8%) were identified as familial PBC in five families. The clinical features of familial PBC were almost comparable to those of non-familial PBC. The distribution of human leukocyte antigens (HLA)-A, -B and -DR in familial PBC showed no specificity. Two new PBC patients were identified in one family in addition to the two originally enrolled PBC patients, resulting in four patients with PBC within the same family. The two new PBC patients had an identical HLA haplotype. On the other hand, one HLA-identical sister of a PBC patient in another family did not develop PBC.

CONCLUSIONS

Primary biliary cirrhosis can exhibit familial clustering without any HLA predisposition, however, a survey of families for PBC could be useful for identifying new patients with PBC in the asymptomatic stage for earlier diagnosis and treatment.

Update on the genetics and genomics of PBC

Despite recent progress, the pathogenic mechanisms governing PBC development, treatment response and outcome remain unknown. This deficiency is in large part due to the complex nature of PBC, wherein various environmental factors may be capable of prompting disease, but only in the context of underlying genetic susceptibility. Identification of genomic loci containing these heritable risk factors has been slowed by the rarity and late onset of PBC, which has made difficult the collection of sufficient numbers of patients and family members for meaningful genetic analyses. Advancements in our ability to catalog the genetic variation in large numbers of individuals at a genome-wide scale, coupled with unprecedented efforts to recruit PBC patients for genetic study, positions us to generate data that could fundamentally change our understanding of PBC and lead to clinical innovation. Indeed, the first genome-wide association study for PBC has been published, in which multiple genes involved with IL12 signaling, a pathway that is being targeted in treatment of other inflammatory conditions, were implicated in disease. However, this study was relatively small in the genome-wide milieu and a significantly expanded effort will be necessary to truly elucidate the genetic architecture of PBC. Moving ahead, cooperation between the groups collecting biospecimens and generating genome-wide data from large numbers of patients with PBC will be essential, not only to increase power for fine mapping and future studies of rare variants and epistasis; but to streamline efforts to perform functional validation of novel discoveries. Here we provide a brief update of the current state of genetics in PBC to form a basis for understanding the considerable progress that is likely to be made in the coming years.

Analysis of HLA-DRB1 polymorphisms in Japanese patients with primary biliary cirrhosis (PBC): The HLA-DRB1polymorphism determines the relative risk of antinuclear antibodies for disease progression in PBC

AIMS

Anti-gp210 and anti-centromere antibodies are different risk factors for the progression of primary biliary cirrhosis (PBC). However, the association of human leukocyte antigen (HLA) polymorphisms with these risk factors is unknown.

METHODS

We determined the HLA-DRB1 genotype in 334 Japanese PBC patients and studied their serum antibodies to gp210 and centromere during the 1-452-month observation period.

RESULTS

Anti-gp210 (odds ratio [OR] 46.56, 95% confidence interval [CI], 9.20-850.1) and anti-centromere antibodies (OR, 2.36, 95% CI, 1.28-4.35) were significant risk factors for jaundice- and nonjaundice-type progression, respectively. HLA-DRB1*0405 and *0803 predisposed patients to anti-gp210 (OR, 1.61, 95% CI, 1.08-2.39) and anti-centromere (OR, 2.30, 95% CI, 1.41-3.73) antibody production, respectively. HLA-DRB1*1502 and *0901 patients were predisposed to nonjaundice-type progression (OR, 1.98, 95% CI, 1.13-3.40 and OR, 1.78, 95% CI, 1.02-3.03), while HLA-DRB1*0803 and *0405 patients were predisposed to disease development (OR, 2.24, 95% CI, 1.48-3.41 and OR, 1.53, 95% CI, 1.11-2.11, respectively). Stratifying patients by HLA-DRB1 alleles revealed that anti-gp210 antibodies was a strong risk factor, regardless of the HLA-DRB1 alleles for jaundice-type progression, while anti-centromere antibodies was a significant risk factor for nonjaundice-type progression in patients with HLA-DRB1*0405 (OR, 6.89, 95% CI, 2.18-26.56) and -DRB1*0803 (OR, 5.42, 95% CI, 1.47-24.62) but not other HLA-DRB1 alleles.

CONCLUSIONS

HLA-DRB1 polymorphisms are significantly associated with not only disease development and progression but also antinuclear antibody production and the determination of the relative risk of antinuclear antibodies that contribute to PBC disease progression.

Genomic variants associated with primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is an autoimmune hepatobiliary disease characterized by immune-mediated injury of small and medium-sized bile ducts, eventually leading to liver cirrhosis. Several studies have addressed PBC immunopathology, and the data support an immune activation leading to autoantibodies and autoreactive T cells acting against the lipoylated 2-oxoacid dehydrogenase complexes. The causes of the disease remain unknown, but environmental factors and genetic susceptibility both contribute to its onset. Over the past two decades several association studies have addressed the role of genetic polymorphisms in PBC pathogenesis and have reported multiple associations. However, only a few studies had sufficient statistical power, and in most cases results were not independently validated. A genome-wide association study has recently been reported, but this too awaits independent confirmation. The aim of this present work is to critically review the numerous studies dedicated to revealing genetic associations in PBC, and to predict the potential for future studies based on these data.

Treatment of Primary Biliary Cirrhosis: A new challenge?

Primary biliary cirrhosis (PBC) is characterized by unknown etiologies, anti-mitochondrial antibodies, injury of the biliary duct and the lack of a definite remedy. The etiologies of PBC have been well-discussed, including microorganisms and xenobiotics as the triggers for initiating the disease, and an abnormality of immune-tolerance. Recently, several animal models of PBC have been developed that may lead to the development of new therapies. Here, we reviewed the articles that address the etiology of PBC and the therapy for this disease for the confirmation of our current positions and future directions.

Primary biliary cirrhosis

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

HLA and autoimmune digestive disease: a clinically oriented review for gastroenterologists

OBJECTIVES

The human leukocyte antigen (HLA) system includes genes involved in graft-vs-host rejection and in immune response. The discovery that HLAs are associated with several diseases led to appealing developments both in basic biomedical research and in clinical medicine, and offered the opportunity to improve the understanding of pathogenesis and classification of diseases, as well as to provide diagnostic and prognostic indicators. The aim of this article is to review the association between HLA alleles and autoimmune digestive disease and its current relationship with modern HLA nomenclature and clinical practice.

METHODS

Articles dealing with the association between HLAs and autoimmune digestive disease (including celiac disease, inflammatory bowel disease, autoimmune hepatitis, sclerosing cholangitis and primary biliary cirrhosis) were searched for using Pubmed and SCOPUS databases from earliest records to January 2008.

RESULTS

The review has provided two sections. In the first, we explain the basic principles of HLA structure, function, and nomenclature, as an introduction to the second section, which describes current associations between HLA alleles and digestive diseases. The clinical implications of each HLA association are critically discussed. Actually, a clinical role for HLA typing is suggested for only a few conditions, e.g., celiac disease.

CONCLUSIONS

The knowledge of current HLA nomenclature and of its association with some digestive diseases such as celiac disease can be useful in clinical practice for diagnostic and prognostic purposes. This can avoid improper HLA typing as well as stressing the need for further studies on other possible clinical applications.

New insights into autoimmune liver diseases

Autoinflammatory liver disease represents an important aspect of global hepatological practice. The three principal disease divisions recognized are autoimmune hepatitis, primary sclerosing cholangitis and primary biliary cirrhosis. Largely, but not exclusively, these diseases are considered to be autoimmune in origin. Increased recognition of outlier and overlap syndromes, changes in presentation and natural history, as well as the increased awareness of IgG4-associated sclerosing cholangitis, all highlight the limitations of the classic terminology. New insights continue to improve the care given to patients, and have arisen from carefully conducted clinical studies, therapeutic trials, as well as genetic and laboratory investigations. The challenges remain to treat patients before liver injury becomes permanent and to prevent the development of organ failure.

Genetics and genomics of primary biliary cirrhosis

The etiologic and pathogenic factors contributing to primary biliary cirrhosis (PBC) development, progression, response to treatment, and outcome remain a mystery. Recognition of the genomic regions harboring risk factors is hindered by the rarity and late onset of PBC. Recent advancements in genomics hold promise for understanding, prevention, and therapy of PBC. Large registries and biospecimen repositories of patients who have PBC, their family members, and controls are needed. Haplotype mapping-based association studies are necessary for defining genetic predisposition. Experimental data will provide the means for fine mapping studies, resequencing efforts, functional experimentation, and elucidation of gene-environment and gene-gene interaction.

Primary biliary cirrhosis and autoantibodies

Fifty years have passed since anti-mitochondrial antibodies were found in patients with primary biliary cirrhosis (PBC). PBC is an autoimmune hepatic disease in which 85-90% of patient antibodies bind to mitochondrial antigens that include pyruvate dehydrogenase complex (PDC)-E2 and other members of the oxaloacid dehydrogenase family. In addition, indirect immunofluorescence (IIF) assays utilizing HEp-2 cell substrates have been used to identify anti-centromere antibodies in 20-30% of PBC sera. These antibodies are generally easily recognized, however, anti-nuclear envelope and anti-multiple nuclear dot antibodies are occasionally more difficult to recognize with certainty by IIF. The use of enzyme linked immunosorbent assays that utilize recombinant gp210 (an autoantigen of the nuclear envelope) and/or sp100 (a protein target represented by multiple nuclear dots) should be particularly considered in anti-mitochondrial antibody negative PBC sera. Although the clinical significance of these antibodies still remains to be determined, there is evidence that the existence of anti-gp210 antibodies are related to poorer prognosis and more aggressive disease progression.

Association of primary biliary cirrhosis with idiopathic thrombocytopenic purpura

Although both primary biliary cirrhosis (PBC) and idiopathic thrombocytopenic purpura (ITP) are autoimmune diseases, the association of the 2 diseases is rare. Here, we report a case of ITP that developed during the follow-up of PBC in a 74-year-old man. The patient had been diagnosed with PBC 12 years previously, and had received treatment with ursodeoxycholic acid. The platelet count decreased from approximately 60 × 10⁹/L to 8 × 10⁹/L, and the association of decompensated liver cirrhosis (PBC) with ITP was diagnosed. Steroid and immune gamma globulin therapy were successful in increasing the platelet count. Interestingly, human leukocyte antigen genotyping detected the alleles DQB1*0601 and DRB1*0803, which are related to both PBC and ITP in Japanese patients. This case suggests common immunogenetic factors might be involved in the development of PBC and ITP.

Genetic background of primary biliary cirrhosis

The clustering of patients in a representative family as well as relatively high concordance rate in monozygotic twins strongly indicate that genetic factors play a crucial role in modulating primary biliary cirrhosis (PBC) by conferring susceptibility to, or providing protection from, the disease. Therefore, much like other autoimmune diseases, intensive investigations have attempted to elucidate which genes are incriminated in the etiology of PBC. So far, a number of genes, including major histocompatibility complex (MHC) class I and II, cytokines and cell surface molecules, have been examined to seek the possibility of whether single nucleotide polymorphisms (SNP) of the gene might be associated with susceptibility to PBC. Nevertheless, it appears that methodologicaldifficulties, mainly the limitation of the number of individuals tested in each study, hamper the detection of a convincing and reproducible link between genetic polymorphisms and the etiology of PBC. Also, the difference in genetic background among several ethnic groups may play a role in concealing the association. In this review, I will highlight the genetic association in PBC, and review the association of genetic polymorphisms with the etiology of PBC, which have been reported in various ethnicities.

Genes and (auto)immunity in primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is a chronic autoimmune cholestatic liver disease most commonly encountered in postmenopausal women; it is characterized by high-titer serum autoantibodies to mitochondrial antigens, elevated serum IgM, progressive destruction of intrahepatic bile ducts, and ultimately liver cirrhosis and failure. The cytopathic mechanisms leading to the selective destruction of intrahepatic cholangiocytes are still largely unknown. The current theory on the pathogenesis of PBC indicated that environmental factors might trigger autoimmunity in genetically susceptible individuals. In fact, genetic predisposition is critical to disease onset and progression, yet peculiar among autoimmune diseases, as indicated by the lack of a strong association with major histocompatibility complex haplotypes. Further, the recently reported concordance rate among monozygotic twins strengthens the importance of genetic factors, while also indicating that additional factors, possibly infectious agents or xenobiotics, intervene to trigger the disease. In this review, the available data regarding the genetic factors associated with PBC susceptibility and progression, as well as the available evidence regarding the immunomediated pathogenesis of PBC, will be critically illustrated and discussed.

Human leukocyte antigen class II alleles in Caucasian women with primary biliary cirrhosis

In the current study, we investigated human leukocyte antigen (HLA) class II alleles in Caucasian women with primary biliary cirrhosis (PBC), a disease that preferentially affects women. Alleles of DRB1, DQA1, and DQB1 were determined by DNA-based HLA typing for women with PBC (n = 72) and healthy women (n = 381). All study subjects were Caucasian. HLA DRB1*08 was significantly increased in women with PBC compared to healthy women. The increase was primarily due to the DRB1*0801 allele, also the most common DRB1*08 allele among controls. DQB1*04 and DQA1*0401 were significantly increased. DRB1*1501, DQA1*0102, and DQB1*0602 were associated with decreased risk. Analyses conducted comparing parous women with PBC to parous healthy women (n = 68 and n = 282, respectively) yielded similar significant results. Although the DRB1*08-DQA1*0401-DQB1*04 haplotype was significantly associated with PBC, consistent with other studies, this haplotype nevertheless represented only 19% (14/72) of all PBC patients and can account for only a minority of the risk of PBC.

From bases to basis: linking genetics to causation in primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is a multifactorial autoimmune disease with inherited and environmental components in pathogenesis. It is exceptional among autoimmune diseases in showing strong heritability according to familial occurrence and monozygotic twins concordance, yet with weak associations with the usual genetic risk elements for autoimmunity, such as the HLA alleles. Among the latter, there is risk (at least in some populations) conferred by HLA DRB1*08 and possibly some protection by DRB1*11. However, the inconsistency among studies on HLA is surprising, given that PBC is a relatively homogenous disease entity. Among non-HLA genes, some studies implicate polymorphisms of genes for cytotoxic T-lymphocyte antigen-4, interleukin-2, or interleukin-10; polymorphisms of the vitamin D receptor could synergize with low sunlight exposure to create deficiency of the immunoregulatory factor, activated vitamin D. A new lead is available from the finding in female subjects with PBC of an increase in the degree of monosomy of the X chromosome that is presumed to carry immune response genes. A further suggested source of inquiry is the apparent protection of African-American women from PBC. Finally, data on inheritance should be sought in PBC by descent methodology, rather than by cross-sectional association studies in cases and control subjects, and based on analysis of a large number of families with an affected member through a worldwide effort.