Extracellular vesicles microRNA analysis in type 1 autoimmune pancreatitis: Increased expression of microRNA-21.

BACKGROUND: The molecular basis of type 1 autoimmune pancreatitis (AIP) remains unclear. Recent attention on the role of extracellular vesicles microRNA (EV miRNA) in immune homeostasis has prompted us to perform an extensive miRNA screening of serum-derived EV in AIP. METHODS: EV miRNA expression was analyzed using microarrays in AIP, chronic pancreatitis (CP), and healthy adult (HC) samples (n = 10 from each group). Differences in signals, > 3 or <1/3 times, represented significant differences in expression. Another cohort of AIP (n = 14), CP (n = 10), and HC (n = 10) samples of EV miRNA was analyzed using reverse-transcription polymerase chain reaction (RT-PCR). miRNA expression in pancreatic tissues was evaluated using in situ hybridization (ISH) in three additional subjects from each group. RESULTS: Signals of eight miRNAs (miR-659-3p, -27a-3p, -99a-5p, -21-5p, -205-5p, -100-5p, -29c-3p, and -125b-1-3p) were significantly higher, while those of two miRNAs (miR-4252 and -5004-5p) were significantly lower in AIP than in HC. EV miR-21-5p was significantly up-regulated in AIP than in HC (P = 0.035) and CP (P = 0.048). The number of miR-21-5p positive inflammatory cells was significantly elevated in AIP than in CP (P = 0.014). CONCLUSIONS: Circulating EVs exhibited altered miRNA expression patterns with elevated miR-21-5p in AIP when compared with those in HC and CP. miR-21-5p was highly expressed in pancreatic inflammatory cells in AIP. Our data suggests that miR-21-5p may be involved in the regulation of effector pathways in the pathophysiology of AIP, thus differentiating AIP from CP.

Pathogen infections and primary biliary cholangitis.

Primary biliary cholangitis (PBC) is a multi-factorial disease caused by the interaction of both genetic predisposition and environmental triggers. Bacterial infection has been investigated most intensively, both epidemiologically and experimentally, as a prime environmental aetiology in PBC. The association of recurrent history of urinary tract infection (UTI) with PBC has been frequently confirmed by several large-scale, case-control studies, despite variation in geographic area or case-finding methods. Escherichia coli is a predominant pathogen in most cases with UTI. Animal studies and molecular mimicry analysis between the human and E. coli E2 subunit of the 2-oxo-acid dehydrogenase complexes demonstrated that E. coli infection is a key factor in breaking immunological tolerance against the mitochondria, resulting in the production of anti-mitochondrial autoantibodies (AMA), the disease-specific autoantibodies of PBC. Novosphingobium aromaticivorans, a ubiquitous xenobiotic-metabolizing bacterium, is another candidate which may be involved in the aetiology of PBC. Meanwhile, improved environmental hygiene and increased prevalence of PBC, especially in males, may argue against the aetiological role of bacterial infection in PBC. Multiple mechanisms can result in the loss of tolerance to mitochondrial autoantigens in PBC; nonetheless, bacterial infection is probably one of the dominant pathways, especially in female patients. Notably, there is a rising prevalence of male patients with PBC. With increasing exposure to environmental xenobiotics in both genders, studies directed towards identifying the environmental culprit with systematically designed case-control studies are much needed to further determine the environmental factors and role of bacterial infections in PBC.

Endogenous interleukin-22 protects against inflammatory bowel disease but not autoimmune cholangitis in dominant negative form of transforming growth factor beta receptor type II mice.

During chronic inflammation, interleukin (IL)-22 expression is up-regulated in both CD4 and CD8 T cells, exerting a protective role in infections. However, in autoimmunity, IL-22 appears to have either a protective or a pathogenic role in a variety of murine models of autoimmunity and, by extrapolation, in humans. It is not clear whether IL-22 itself mediates inflammation or is a by-product of inflammation. We have taken advantage of the dominant negative form of transforming growth factor beta receptor type II (dnTGF-ßRII) mice that develop both inflammatory bowel disease and autoimmune cholangitis and studied the role and the biological function of IL-22 by generating IL-22(-/-) dnTGF-ßRII mice. Our data suggest that the influence of IL-22 on autoimmunity is determined in part by the local microenvironment. In particular, IL-22 deficiency exacerbates tissue injury in inflammatory bowel disease, but has no influence on either the hepatocytes or cholangiocytes in the same model. These data take on particular significance in the previously defined effects of IL-17A, IL-12p40 and IL-23p19 deficiency and emphasize that, in colitis, there is a dominant role of IL-23/T helper type 17 (Th17) signalling. Furthermore, the levels of IL-22 are IL-23-dependent. The use of cytokine therapy in patients with autoimmune disease has significant potential, but must take into account the overlapping and often promiscuous effects that can theoretically exacerbate inflammation.

Serum microRNAs as novel biomarkers for primary sclerosing cholangitis and cholangiocarcinoma.

The diagnosis of primary sclerosing cholangitis (PSC) is difficult due to the lack of sensitive and specific biomarkers, as is the early diagnosis of cholangiocarcinoma (CC), a complication of PSC. The aim of this study was to identify specific serum miRNAs as diagnostic biomarkers for PSC and CC. The levels of 667 miRNAs were evaluated in 90 human serum samples (30 PSC, 30 CC and 30 control subjects) to identify disease-associated candidate miRNAs (discovery phase). The deregulated miRNAs were validated in an independent cohort of 140 samples [40 PSC, 40 CC, 20 primary biliary cirrhosis (PBC) and 40 controls]. Receiver operating characteristic (ROC) curves were established and only miRNAs with an area under the curve (AUC) > 0·70 were considered useful as biomarkers. In the discovery phase we identified the following: 21 miRNAs expressed differentially in PSC, 33 in CC and 26 in both in comparison to control subjects as well as 24 miRNAs expressed differentially between PSC and CC. After the validation phase, miR-200c was found to be expressed differentially in PSC versus controls, whereas miR-483-5p and miR-194 showed deregulated expression in CC compared with controls. We also demonstrate a difference in the expression of miR-222 and miR-483-5p in CC versus PSC. Combination of these specific miRNAs further improved the specificity and accuracy of diagnosis. This study provides a basis for the use of miRNAs as biomarkers for the diagnosis of PSC and CC.

The cumulative effects of known susceptibility variants to predict primary biliary cirrhosis risk.

Multiple genetic variants influence the risk for development of primary biliary cirrhosis (PBC). To explore the cumulative effects of known susceptibility loci on risk, we utilized a weighted genetic risk score (wGRS) to evaluate whether genetic information can predict susceptibility. The wGRS was created using 26 known susceptibility loci and investigated in 1840 UK PBC and 5164 controls. Our data indicate that the wGRS was significantly different between PBC and controls (P=1.61E-142). Moreover, we assessed predictive performance of wGRS on disease status by calculating the area under the receiver operator characteristic curve. The area under curve for the purely genetic model was 0.72 and for gender plus genetic model was 0.82, with confidence limits substantially above random predictions. The risk of PBC using logistic regression was estimated after dividing individuals into quartiles. Individuals in the highest disclosed risk group demonstrated a substantially increased risk for PBC compared with the lowest risk group (odds ratio: 9.3, P=1.91E-084). Finally, we validated our findings in an analysis of an Italian PBC cohort. Our data suggested that the wGRS, utilizing genetic variants, was significantly associated with increased risk for PBC with consistent discriminant ability. Our study is a first step toward risk prediction for PBC.

Immunological potential of cytotoxic T lymphocyte antigen 4 immunoglobulin in murine autoimmune cholangitis.

Cytotoxic T lymphocyte antigen 4 (CTLA-4) immunoglobulin (Ig) is an important regulator of T cell activation and a fusion protein directed at CD80 and CD86; it blocks co-stimulatory signalling and T cell activation. We have taken advantage of a murine model of human primary biliary cirrhosis (PBC), mice expressing a transforming growth factor (TGF)-ß receptor II dominant negative (dnTGF-ßRII) transgene to address the potential therapeutic efficacy of CTLA-4 Ig. To mimic patients with PBC at different stages or duration of disease, we treated mice with either CTLA-4 Ig or control IgG three times weekly from 3 to 12 or 24 weeks of age, or from 12 to 24 weeks of age. CTLA-4 Ig treatment from 3 weeks of age significantly reduced liver inflammation to 12 weeks of age. Treatment initiated at 12 weeks of age also ameliorated the autoimmune cholangitis at 24 weeks of age. However, in mice treated at 3 weeks of age, suppression of liver inflammation was not sustained and colitis was aggravated when treatment was extended to 24 weeks of age. Our data indicate that, in dnTGF-ßRII mice, CTLA-4 Ig treatment has short-term beneficial effects on autoimmune cholangitis, but the effect varies according to duration of treatment and the time in which therapy was initiated. Further dissection of the events that lead to the reduction in therapeutic effectiveness of CTLA-4 Ig will be critical to determining whether such efforts can be applied to human PBC.

Innate immunity drives xenobiotic-induced murine autoimmune cholangitis.

Although primary biliary cirrhosis (PBC) is considered a model autoimmune disease, it has not responded therapeutically to traditional immunosuppressive agents. In addition, PBC may recur following liver transplantation, despite the absence of major histocompatibility complex (MHC) matching, in sharp contrast to the well-known paradigm of MHC restriction. We have suggested previously that invariant natural killer T (iNK T) cells are critical to the initiation of PBC. In this study we have taken advantage of our ability to induce autoimmune cholangitis with 2-octynoic acid, a common component of cosmetics, conjugated to bovine serum albumin (2-OA-BSA), and studied the natural history of pathology in mice genetically deleted for CD4 or CD8 following immunization with 2-OA-BSA in the presence or absence of α-galactosylceramide (α-GalCer). In particular, we address whether autoimmune cholangitis can be induced in the absence of traditional CD4 and CD8 responses. We report herein that CD4 and CD8 knock-out mice immunized with 2-OA-BSA/PBS or 2-OA-BSA/α-GalCer develop anti-mitochondrial antibodies (AMAs), portal infiltrates and fibrosis. Indeed, our data suggest that the innate immunity is critical for immunopathology and that the pathology is exacerbated in the presence of α-GalCer. In conclusion, these data provide not only an explanation for the recurrence of PBC following liver transplantation in the absence of MHC compatibility, but also suggest that effective therapies for PBC must include blocking of both innate and adaptive pathways.

Successful immunotherapy of autoimmune cholangitis by adoptive transfer of forkhead box protein 3(+) regulatory T cells.

Treatment of primary biliary cirrhosis (PBC) has lagged behind that of other autoimmune diseases. In this study we have addressed the potential utility of immunotherapy using regulatory T cells (Treg ) to treat murine autoimmune cholangitis. In particular, we have taken advantage of our ability to produce portal inflammation and bile duct cell loss by transfer of CD8(+) T cells from the dominant negative form of transforming growth factor beta receptor type II (dnTGF-ßRII) mice to recombination-activating gene (Rag)1(-/-) recipients. We then used this robust established adoptive transfer system and co-transferred CD8(+) T cells from dnTGF-ßRII mice with either C57BL/6 or dnTGF-ßRII forkhead box protein 3 (FoxP3(+) ) T cells. Recipient mice were monitored for histology, including portal inflammation and intralobular biliary cell damage, and also included a study of the phenotypical changes in recipient lymphoid populations and local and systemic cytokine production. Importantly, we report herein that adoptive transfer of Treg from C57BL/6 but not dnTGF-ßRII mice significantly reduced the pathology of autoimmune cholangitis, including decreased portal inflammation and bile duct damage as well as down-regulation of the secondary inflammatory response. Further, to define the mechanism of action that explains the differential ability of C57BL/6 Treg versus dnTGF-ßRII Treg on the ability to down-regulate autoimmune cholangitis, we noted significant differential expression of glycoprotein A repetitions predominant (GARP), CD73, CD101 and CD103 and a functionally significant increase in interleukin (IL)-10 in Treg from C57BL/6 compared to dnTGF-ßRII mice. Our data reflect the therapeutic potential of wild-type CD4(+) FoxP3(+) Treg in reducing the excessive T cell responses of autoimmune cholangitis, which has significance for the potential immunotherapy of PBC.

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

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

Anti-CD4 treatment inhibits autoimmunity in scurfy mice through the attenuation of co-stimulatory signals.

A major concept in autoimmunity is that disruption of Foxp3(+) regulatory T cells (Tregs) predisposes to breach of tolerance. This is exemplified by the Foxp3-linked disorder termed IPEX (immunodysregulation, polyendocrinopathy, enteropathy, X-linked) which affects newborn children. There has been considerable clinical interest in the role of non-depleting anti-CD4 antibodies as a means of upregulating the function of Foxp3(+) Tregs in order to control detrimental inflammatory responses such as transplant rejection. However, according to the paradigm of a Treg-dependent mechanism of action, the effectiveness of anti-CD4 antibodies as a therapy for human autoimmune diseases is unclear considering that Treg function might be intrinsically impaired. Specifically, anti-CD4 therapy is expected to fail in patients suffering from the IPEX syndrome due to the lack of functional Foxp3(+) Tregs. Taking advantage of natural Foxp3 mutant scurfy (sf) mice closely resembling the IPEX syndrome, and genetically engineered mice depleted of Foxp3(+) Tregs, we report here that anti-CD4 treatment induces tolerance independent of Foxp3(+) Tregs. This so far undefined mechanism is dependent on the recessive non-infectious tolerization of autoreactive T cells. Treg-independent tolerance alone is powerful enough to suppress both the onset and severity of autoimmunity and reduces clinically relevant autoantibody levels and liver fibrosis. Mechanistically, tolerance induction requires the concomitant activation of autoreactive T cells and is associated with the down-regulation of the co-stimulatory TNF-receptor superfamily members OX40 and CD30 sustaining CD4(+) T cell survival. In the light of ongoing clinical trials, our results highlight an unexpected potency of anti-CD4 antibodies for the treatment of autoimmune diseases. Particularly, CD4 blockade might represent a novel therapeutic option for the human IPEX syndrome.

Pathway-based analysis of primary biliary cirrhosis genome-wide association studies.

Genome-wide association studies (GWAS) have successfully identified several loci associated with primary biliary cirrhosis (PBC) risk. Pathway analysis complements conventional GWAS analysis. We applied the recently developed linear combination test for pathways to datasets drawn from independent PBC GWAS in Italian and Canadian subjects. Of the Kyoto Encyclopedia of Genes and Genomes and BioCarta pathways tested, 25 pathways in the Italian dataset (449 cases, 940 controls) and 26 pathways in the Canadian dataset (530 cases, 398 controls) were associated with PBC susceptibility (P<0.05). After correcting for multiple comparisons, only the eight most significant pathways in the Italian dataset had FDR <0.25 with tumor necrosis factor/stress-related signaling emerging as the top pathway (P=7.38 × 10⁻4, FDR=0.18). Two pathways, phosphatidylinositol signaling and hedgehog signaling, were replicated in both datasets (P<0.05), and subjected to two additional complementary pathway tests. Both pathway signals remained significant in the Italian dataset on modified gene set enrichment analysis (P<0.05). In both GWAS, variants nominally associated with PBC were significantly overrepresented in the phosphatidylinositol pathway (Fisher exact P<0.05). These results point to established and novel pathway-level associations with inherited predisposition to PBC that, on further independent replication and functional validation, may provide fresh insights into PBC etiology.

Human intrahepatic biliary epithelial cells engulf blebs from their apoptotic peers.

The phagocytic clearance of apoptotic cells is critical for tissue homeostasis; a number of non-professional phagocytic cells, including epithelial cells, can both take up and process apoptotic bodies, including the release of anti-inflammatory mediators. These observations are particularly important in the case of human intrahepatic biliary cells (HiBEC), because such cells are themselves a target of destruction in primary biliary cirrhosis, the human autoimmune disease. To address the apoptotic ability of HiBECs, we have focused on their ability to phagocytize apoptotic blebs from autologous HiBECs. In this study we report that HiBEC cells demonstrate phagocytic function from autologous HiBEC peers accompanied by up-regulation of the chemokines CCL2 [monocyte chemotactic protein-1 (MCP-1)] and CXCL8 [interleukin (IL)-8]. In particular, HiBEC cells express the phagocytosis-related receptor phosphatidylserine receptors (PSR), implying that HiBECs function through the 'eat-me' signal phosphatidylserine expressed by apoptotic cells. Indeed, although HiBEC cells acquire antigen-presenting cell (APC) function, they do not change the expression of classic APC function surface markers after engulfment of blebs, both with and without the presence of Toll-like receptor (TLR) stimulation. These results are important not only for understanding of the normal physiological function of HiBECs, but also explain the inflammatory potential and reduced clearance of HiBEC cells following the inflammatory cascade in primary biliary cirrhosis.

Characteristics of splenic CD8+ T cell exhaustion in patients with hepatitis C.

There is increasing interest in the role of T cell exhaustion and it is well known that the natural history of chronic hepatitis C virus infection (HCV) is modulated by CD8(+) T cell immunobiology. There are many pathways that alter the presence of exhaustive T cells and, in particular, they are functionally impaired by inhibitory receptors, such as programmed death-1 (PD-1) and T cell immunoglobulin and mucin domain-containing protein 3 (Tim-3). We obtained spleen, liver and peripheral blood (before and after splenectomy) lymphoid cells from 25 patients with HCV-related cirrhosis undergoing liver transplantation for end-stage disease or splenectomy for portal hypertension. In all samples we performed an extensive phenotypic study of exhaustion markers [PD-1, Tim-3, interferon (IFN)-γ) and their ligands (PD-L1, PD-L2, galectin-9] in CD8(+) T cell subpopulations (both total and HCV-specific) and in antigen-presenting cells (APC; monocytes and dendritic cells). In the spleen, total and HCV-specific CD8(+) T cells demonstrated enhanced markers of exhaustion, predominantly in the effector memory subpopulation. Similarly, splenic APC over-expressed inhibitory receptor ligands when compared to peripheral blood. Finally, when peripheral blood CD8(+) T cells were compared before and after splenectomy, markers of exhaustion were reduced in splenic CD8(+) T cells and APC. Our data in HCV-related cirrhosis suggest that CD8(+) T cells in the spleen manifest a significantly higher exhaustion compared to peripheral blood and may thus contribute to the failure to control HCV. Counteracting this process may contribute to inducing an effective immune response to HCV.

Anti-CD40 ligand monoclonal antibody delays the progression of murine autoimmune cholangitis.

While there have been significant advances in our understanding of the autoimmune responses and the molecular nature of the target autoantigens in primary biliary cirrhosis (PBC), unfortunately these data have yet to be translated into new therapeutic agents. We have taken advantage of a unique murine model of autoimmune cholangitis in which mice expressing a dominant negative form of transforming growth factor ß receptor II (dnTGFßRII), under the control of the CD4 promoter, develop an intense autoimmune cholangitis associated with serological features similar to human PBC. CD40-CD40 ligand (CD40L) is a major receptor-ligand pair that provides key signals between cells of the adaptive immune system, prompting us to determine the therapeutic potential of treating autoimmune cholangitis with anti-CD40L antibody (anti-CD40L; MR-1). Four-week-old dnTGFßRII mice were injected intraperitoneally with either anti-CD40L or control immunoglobulin (Ig)G at days 0, 2, 4 and 7 and then weekly until 12 or 24 weeks of age and monitored for the progress of serological and histological features of PBC, including rigorous definition of liver cellular infiltrates and cytokine production. Administration of anti-CD40L reduced liver inflammation significantly to 12 weeks of age. In addition, anti-CD40L initially lowered the levels of anti-mitochondrial autoantibodies (AMA), but these reductions were not sustained. These data indicate that anti-CD40L delays autoimmune cholangitis, but the effect wanes over time. Further dissection of the mechanisms involved, and defining the events that lead to the reduction in therapeutic effectiveness will be critical to determining whether such efforts can be applied to PBC.

Classical HLA-DRB1 and DPB1 alleles account for HLA associations with primary biliary cirrhosis.

Susceptibility to primary biliary cirrhosis (PBC) is strongly associated with human leukocyte antigen (HLA)-region polymorphisms. To determine if associations can be explained by classical HLA determinants, we studied Italian, 676 cases and 1440 controls, genotyped with dense single-nucleotide polymorphisms (SNPs) for which classical HLA alleles and amino acids were imputed. Although previous genome-wide association studies and our results show stronger SNP associations near DQB1, we demonstrate that the HLA signals can be attributed to classical DRB1 and DPB1 genes. Strong support for the predominant role of DRB1 is provided by our conditional analyses. We also demonstrate an independent association of DPB1. Specific HLA-DRB1 genes (*08, *11 and *14) account for most of the DRB1 association signal. Consistent with previous studies, DRB1*08 (P=1.59 × 10(-11)) was the strongest predisposing allele, whereas DRB1*11 (P=1.42 × 10(-10)) was protective. Additionally, DRB1*14 and the DPB1 association (DPB1*03:01; P=9.18 × 10(-7)) were predisposing risk alleles. No signal was observed in the HLA class 1 or class 3 regions. These findings better define the association of PBC with HLA and specifically support the role of classical HLA-DRB1 and DPB1 genes and alleles in susceptibility to PBC.

Use of RNA interference to modulate liver adenoma development in a murine model transgenic for hepatitis B virus.

Chronic hepatitis B virus (HBV) infection is closely related to the development of severe liver complications, including hepatocellular carcinoma. In previous studies, we reported that in vivo long-term HBV suppression in transgenic mice can be achieved without apparent toxicity by short hairpin RNA sequentially delivered using adeno-associated viral (AAV) vectors of different serotypes. Our goal herein was to address the clinical utility of this delivery system and, in particular, to determine whether RNA interference (RNAi) and its ability to induce long-term HBV suppression will modulate the development of HBV-associated liver pathology. As a model system, we used a unique HBV transgenic mouse model, containing a 1.3 times over length of the HBV genome, on the ICR mouse background. These transgenic mice produce high serum HBV titers comparable with human chronic HBV patients, and, importantly, manifest characteristic HBV-associated pathology, including progressive hepatocellular injury and the development of hepatocellular adenoma. Using this system, we injected animals with AAV vectors expressing either HBV-specific or a control luciferase-specific short hairpin RNA and followed animals for a total of 18 months. We report herein that AAV-mediated RNAi therapy profoundly inhibits HBV replication and gene expression, with a significant reduction in hepatic regeneration, liver enzymes and, importantly, the appearance of liver adenomas. Indeed, the therapeutic effect of RNAi correlated with the reduction in HBV titers. Our data demonstrate that appropriately designed RNAi therapy has the potential to prevent formation of HBV-associated hepatocellular adenoma.

X chromosome gene methylation in peripheral lymphocytes from monozygotic twins discordant for scleroderma.

Scleroderma (SSc) is a rare connective tissue disease characterized by fibrosis, microvasculopathy and autoimmune features. The role of genetics is limited in SSc, as suggested by similar concordance rates in monozygotic and dizygotic twin pairs, while environmental factors may act through epigenetic changes, as demonstrated for specific genes. Further, sex chromosome changes have been reported in SSc and may explain the female preponderance. In the present study we compared the methylation profile of all X chromosome genes in peripheral blood mononuclear cells from monozygotic twins discordant (n=7) and concordant (n=1) for SSc. Methylated DNA immunoprecipitations from each discordant twin pair were hybridized to a custom-designed array included 998 sites encompassing promoters of all X chromosome genes and randomly chosen autosomal genes. Biostatistical tools identified sites with an elevated probability to be consistently hypermethylated (n=18) or hypomethylated (n=25) in affected twins. Identified genes include transcription factors (ARX, HSFX1, ZBED1, ZNF41) and surface antigens (IL1RAPL2, PGRMC1), and pathway analysis suggests their involvement in cell proliferation (PGK1, SMS, UTP14A, SSR4), apoptosis (MTM1), inflammation (ARAF) and oxidative stress (ENOX2). In conclusion, we propose that X chromosome genes with different methylation profiles in monozygotic twin pairs may constitute candidates for SSc susceptibility.

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

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

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

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

Modulation of CD4⁺ T cell responses following splenectomy in hepatitis C virus-related liver cirrhosis.

Dysfunction of T cells is a common feature in chronic persistent viral infections, including hepatitis C virus (HCV), and although hepatic and peripheral T cells have been studied extensively in chronic HCV hepatitis, the role of splenic T cell responses in such patients is poorly defined. This is an important issue, as thrombocytopenia is a complication of HCV-related liver cirrhosis (LC), due to splenic platelet sequestration and bone marrow suppression; splenectomy has been proposed to treat such patients. Herein, we studied peripheral blood mononuclear cells (PBMC) and splenic lymphoid subpopulations from a total of 22 patients, including 15 with HCV-related LC with marked thrombocytopenia treated with splenectomy, and seven controls. CD4(+) T cells from peripheral blood and spleen were isolated and phenotype and function evaluated. Splenic CD4(+) T cells in patients with LC expressed molecules associated with inhibitory signalling, including increased frequency of negative markers such as cytotoxic T lymphocyte associated antigen-4 (CTLA-4) and programmed death 1 (PD-1) and decreased production of cytokines. Patients with LC manifest higher levels of splenic CD4(+) regulatory T cells and PD-L1- and PD-L2-expressing cells than controls. Blocking of PD-1/PD-1 ligand interaction reconstituted proliferative and cytokine responses of splenic mononuclear cells (SMC) from patients with LC. Splenectomy was followed by an increase in the ratio of interferon (IFN)-γ to interleukin (IL)-10 and a reduction of PD-1-expressing CD4(+) T cells in peripheral blood. Our data suggest that peripheral tolerance is promoted by the spleen in LC via the up-regulated expression of PD-1 ligands.