Serial analysis of antimitochondrial antibody in patients with primary biliary cirrhosis

FcγRIIB expression increases during primary biliary cholangitis

Primary biliary cholangitis (PBC) is a severe disease with unknown aetiology and poor prognosis owing to ineffective treatment. B-cell antibodies play a regulatory role during immune responses; therefore, their role in PBC should not be overlooked. Fcγ receptors (FcγRs) of IgG and cell surface glycoproteins play an important role in autoimmune and infectious disease prevention. In this study, 60 patients with PBC and 35 healthy controls (HCs) were recruited. The number of B cells and the expression of the FcγRIIB on the peripheral blood mononuclear cells of patients with PBC were evaluated using FACS. The concentrations of soluble FcγRs were determined using ELISA, and intrahepatic FcγRIIB and CD19 expressions in patients with PBC were visualised using IHC. FcγRIIB expression in B cells was significantly higher in patients with PBC than in HCs (P < 0.0001). The soluble FcγRIIB levels in the plasma were higher in patients with PBC than in HCs (P = 0.0009). Notably, these levels were reduced by treatment with ursodeoxycholic acid (P = 0.0236). CD19 and FcγRIIB expression increased in the liver of patients with PBC relative to that in HCs. These findings can provide new insights into PBC pathogenesis and can aid the future development of treatment strategies.

Peroxisome Proliferator-Activated Receptors Regulate Hepatic Immunity and Assist in the Treatment of Primary Biliary Cholangitis

Fibrates, which are agonists of peroxisome proliferator-activated receptor alpha, have received increasing attention in the treatment of primary biliary cholangitis. Reduced alkaline phosphatase levels and improved clinical outcomes were observed in patients with primary biliary cholangitis with an inadequate response to ursodeoxycholic acid (UDCA) monotherapy4 when treated with bezafibrate or fenofibrate combined with UDCA. In contrast to obeticholic acid, which exacerbates pruritus in patients, fibrates have been shown to relieve pruritus. Clinical trial outcomes show potential for the treatment of primary biliary cholangitis by targeting peroxisome proliferator-activated receptors. It is currently agreed that primary biliary cholangitis is an autoimmune-mediated cholestatic liver disease, and peroxisome proliferator-activated receptor is a nuclear receptor that regulates the functions of multiple immune cells, thus playing an important role in regulating innate and adaptive immunity. Therefore, this review focuses on the immune disorder of primary biliary cholangitis and summarizes the regulation of hepatic immunity when peroxisome proliferator-activated receptors are targeted for treating primary biliary cholangitis.

Anti-Mitochondrial Antibody Titers Decrease Over Time in Primary Biliary Cholangitis Patients With Ursodeoxycholic Acid Therapeutic Response: A Cohort Study Followed Up to 28 Years

Background

How anti-mitochondrial antibody (AMA) and liver biochemistry levels change in primary biliary cholangitis (PBC) patients treated with ursodeoxycholic acid (UDCA) remains unclear.

Methods

A 28-year cohort of 157 PBC patients was conducted. Patients with alkaline phosphatase (Alk-p) levels >1.67 × upper limit of normal after 1 year of UDCA treatment were considered nonresponders.

Results

At baseline, of 157 (mean age: 54.41 years), 136 (86.6%) were female, 51 (32.5%) had cirrhosis, and 128 (81.5%) had detectable AMAs (immunoglobulin G). UDCA nonresponders (n=61) were younger and had higher Alk-p and total bilirubin levels and cirrhosis rates than UDCA responders (n=84). Alk-p levels and cirrhosis were negatively associated with UDCA response. Regardless of cirrhosis and UDCA response, most PBC patients had decreased Alk-p and γ-glutamyltransferase levels at last follow-up (up to 28.73 years) compared with baseline levels. Patients with baseline cirrhosis (2.78 ± 2.56 vs. 6.84 ± 9.00 mg/dL, p=0.024) and UDCA nonresponders (2.54 ± 2.19 vs. 4.51 ± 6.99 mg/dL, p=0.006) had increased total bilirubin levels while patients without cirrhosis (AST: 91.5 ± 84.5 vs. 58.9 ± 43.7 U/L, p<0.001; ALT: 107.3 ± 122.5 vs. 50.7 ± 36.8 U/L, p<0.001) and UDCA responders (AST: 83.8 ± 101.3 vs. 45.58 ± 38.42 U/L, p=0.014; ALT: 95.10 ± 144.6 vs. 39.12 ± 30.65 U/L, p=0.009) had decreased aminotransferase levels. Only UDCA responders had decreased AMA titers from 1 year after UDCA treatment (p=0.028) until the last follow-up (p<0.001).

Conclusions

UDCA responders exhibited decreased AMA titers 1 year after treatment. Regardless of UDCA response, PBC patients showed improved cholestatic features, but only UDCA responders and patients without baseline cirrhosis exhibited attenuated hepatobiliary damage following UDCA treatment.

Antigen Reactivity and Clinical Significance of Autoantibodies Directed Against the Pyruvate Dehydrogenase Antigen Complex in Patients With Connective Tissue Disease

Introduction

Antimitochondrial antibodies (AMAs) are the hallmark of primary biliary cholangitis (PBC) but can be identified also in patients with connective tissue disease, namely, systemic sclerosis (SSc). Protein immunoprecipitation (IP) and IP-Western blot (WB) can be used to confirm AMA positivity directed at the pyruvate dehydrogenase complex (PDC) subunits E1α, E1β, E2/E3, and E3BP in patients showing a cytoplasmic reticular pattern at indirect immunofluorescence when performed in a screening setting before the onset of overt cholestasis in rheumatic patients.

Patients and Methods

We studied sera from 285 patients affected by connective tissue disease [SSc, n = 144; dermato/polymyositis (DM/PM), n = 56; and undifferentiated connective tissue disease (UCTD), n = 85] by indirect immunofluorescence (IIF), protein-IP, and IP-WB to identify specific PDC subunits recognized by AMA.

Results

Twenty percent (57/285) of sera from patients with connective tissue disease had a cytoplasmic reticular pattern at IIF, and in 77% (44/57, including 20 SSc, 12 PM/DM, and 12 UCTD) of these, we detected different titers of autoantibodies against the PDC subunits, specifically against PDC-E2. Among these sera, 4 (9%) tested positive for anti-E1α, 15 (34%) for anti-E1β, and 16 (36%) for anti-E3BP. Four of the 20 AMA-positive SSc cases (20%) had been already diagnosed with PBC, and all were positive for autoantibodies against the subunits PDC-E2, E3, and E3BP.

Conclusions

Using IIF and IP, we confirm that autoantibodies against the PDC components are detected in rheumatic patients with PBC or without liver dysfunction. In view of the strong predictive value of AMA for PBC, a strict follow-up of these latter patients is warranted for an early diagnosis of the disease.

Detection of anti-mitochondrial 2-oxoacid dehydrogenase complex subunit's antibodies for the diagnosis of primary biliary cholangitis

Anti-mitochondrial antibodies (AMA), directed against the E2 subunits of the 2-oxo acid dehydrogenase complexes, are markers of Primary Biliary Cholangitis (PBC), a chronic autoimmune liver disease. However, the clinical significance of subunits-specific AMA type PDC-E2 -E2 subunit of the pyruvate dehydrogenase complex-, BCOADC-E2 -E2 subunit of the branched-chain 2-oxo acid dehydrogenase complex-, OGDC-E2 -E2 subunit of the 2-oxo-glutarate dehydrogenase complex- and nPDC -native pyruvate dehydrogenase complex (M2-AMA) . Is not well known, and not all AMA specificities are associated with PBC. The aim of the study was to show the usefulness of the number and combination of subunits-specific AMA positive for the diagnosis of PBC. We detected AMA by indirect immunofluorescence (IIF-AMA) and M2-AMA by dot-blot. We studied the relationship of AMA with some clinical and laboratory variables in 307 patients (37% PBC) with positive dot-blot for M2-AMA. In PBC patients, we detected different E2 subunits of the 2-oxo acid dehydrogenase complexes antibodies (M2-AMA): 82.9% were specific for nPDC, 64.5% for PDC-E2, 44.4% for BCOADC-E2, and 9.6% for OGDC-E2. IIF and dot-blot tests achieved a Area Under the Receiver Operating Characteristic Curve (ROC AUC) of 0.674 (1: 320 cut-off titer, Sensibility (Se) 64.7%, Specificity (Sp) 63.4%) and 0.663 (three specificities M2-AMA, Se 43%, Sp 81.2%), respectively. The detection of different E2 subunits of the 2-oxo acid dehydrogenase complexes antibodies (M2-AMA) by dot-blot showed different ROC AUC: anti-PDC-E2 showed an AUC of 0.610, a Se of 43.7%, and a Sp of 76.4%. Finally, the combined detection of nPDC/BCOADC-E2/PDC-E2 reached an AUC of 0.6095, a Se of 59.6%, and a Sp of 70.2%.The identification of two M2-AMA specificities through dot-blot increased PBC odds ratio (OR) by 2.05 (p:0.031), as compared to the identification of one specificity. Moreover, the identification of three and four specificities increased OR by 4.63 (p:0.000) and by 21.53 (p:0.006), respectively. nPDC/OGDC-E2/PDC-E2 and nPDC/OGDC-E2/BCOADC-E2/PDC-E2 combinations increased PBC OR by 10.04 (p:0.034), as compared to any other combination. 1:320 and 1:640 IIF-AMA increased PBC OR by 4.93 (p:0.009) and 7.67 (p:0.001), respectively, as compared to IIF-AMA titers equal to or less than 1:160. M2-AMA dot-blot was less sensitive but more specific than IIF-AMA, with similar predictive capacity for PBC. Increased numbers of M2-AMA specificities clearly increased the risk of PBC. Some combinations were strongly related to PBC (nPDC/BCOADC-E2/PDC-E2), but others were not (one single M2-AMA, and nPDC plus PDC-E2). M2-AMA dot-blot was less sensitive but more specific than IIF-AMA, with similar predictive capacity for PBC. Increased numbers of M2-AMA specificities clearly increased the risk of PBC, being some combinations, such as nPDC/BCOADC-E2/PDC-E2, more related to PBC than others. Finally, the determination of the number of M2-AMA specificities was more useful than the particular subunit target for PBC diagnosis. In conclusion, the study of the number of M2-AMA specificities by dot-blot should definitely be considered for PBC diagnosis.

Clinical significance of IgG antimitochondrial M2 antibody levels in primary biliary cholangitis: A single center study from China

Background and objective

The relationship between antimitochondrial antibody (AMA) levels and the severity or prognosis of primary biliary cholangitis (PBC) is unclear. This study explored the clinical significance of serum IgG antimitochondrial M2 antibody (IgG-M2) levels.

Methods

From 2008 to 2017, a retrospective analysis was conducted with PBC patients who had available quantitative values of serum IgG-M2 levels obtained with ELISA based on triple expression hybrid clones. The patients were divided into two groups based on high and low concentrations of IgG-M2. Baseline parameters, the incidence of adverse events, and prognosis were compared.

Results

Among the 530 PBC patients, the levels of albumin, cholinesterase, hemoglobin, fibrinogen and triglycerides and the red blood cell count were significantly lower in the high-concentration group than in the low-concentration group (n = 263, 49.6%). The red cell distribution width (RDW) and levels of serum immunoglobulin (Ig) G, IgM and IgA were significantly higher in the high-concentration group than in the low-concentration group. Spearman’s correlation analysis suggested that the correlation between the above baseline indicators and IgG-M2 levels was statistically significant but weak (r < 0.2, P < 0.05). In total, 203 patients were followed up, of whom 87 (42.9%) were in the high-concentration group. During the median follow-up period of 52 months (range: 28–75), 121 (59.6%) experienced hepatic decompensation, and 37 (18.2%) died or underwent liver transplantation. There was no significant difference in the incidence of complications or survival (log-rank test: P = 0.079) between the two groups. One year after ursodeoxycholic acid (UDCA) treatment, the two groups had similar responses. In addition, the levels of IgG-M2 did not fluctuate significantly during treatment.

Conclusion

IgG-M2 levels were not related to the disease severity, prognosis or efficacy of UDCA. The levels of IgG-M2 did not change significantly during treatment.

Antibodies to the Muscarinic Acetylcholine Receptor M3 in Primary Biliary Cholangitis Inhibit Receptor Function on Cholangiocytes

Background and Aims: In primary biliary cholangitis (PBC), antibodies to a peptide of the muscarinic acetylcholine receptor 3 (mAChR3) have been described. Since the mAChR3 is expressed on cholangiocytes and mAChR3-signaling is involved in the pathogenesis of chronic inflammatory biliary diseases, we wanted to investigate whether anti-mAChR3-antibodies influence the function of the receptor and the proliferative response of cholangiocytes. Methods: Immunoglobulins were isolated by ammonium sulfate precipitation using sera from patients with PBC (n = 63) and with other chronic liver disorders (n = 150). All immunoglobulins were analyzed by a luminometric assay using Chinese hamster ovary (CHO) cells overexpressing the mAChR3 and cholangiocytes (TFK-1-cells) expressing the receptor constitutively. Cell proliferation was measured by ³H-thymidine assay. PBC patients were also analyzed in the follow-up. Results: Antibodies inhibiting the mAChR3 were found in 49 and 79% of PBC patients using CHO-cells or TFK-1-cells, respectively, but only in up to 26% of controls (p < 0.01). Stimulatory antibodies were hardly detected. Antibody reactivity only marginally changed during the course of the disease, independently of the choice of treatment (ursodeoxycholic acid, immunosuppressive therapy, or no medication). There was no correlation with laboratory, clinical or histological parameters, but the antibodies were more frequently found in PBC patients with a benign course (96%) than in patients with active disease progressing to late stages within 10 years (57%; p < 0.01). Proliferation of cells was not influenced by immunoglobulins from PBC-patients. Conclusion: Sera from patients with PBC contain inhibitory antibodies to the mAChR3 on cholangiocytes (TFK-1 cells) without influencing TFK-1-cell proliferation. These antibodies were predominantly observed in patients with non-progressing PBC.

Evolving liver inflammation in biochemically normal individuals with anti-mitochondria antibodies

Background

Anti-mitochondria autoantibodies (AMA) occur in > 95% primary biliary cholangitis (PBC) patients. Biochemically normal AMA-positive (BN/AMA+) individuals, occasionally noticed by indirect immunofluorescence (IIF) on HEp-2 cells and confirmed in AMA-specific assays, may represent early stages of PBC. The Enhanced Liver Fibrosis (ELF) score is a surrogate marker for liver fibrosis. This prospective study investigated the ELF score in BN/AMA+ individuals and PBC patients, considering autoantibody avidity and serum levels along the years.

Methods

327 samples from 35 PBC and 59 BN/AMA+ were prospectively obtained in average 3.83 (range 0.50-7.40) years apart. Samples were tested by IIF on rat-kidney (IIF-AMA), western-blot for AMA (WB-AMA), and ELISA for antibodies against pyruvate-dehydrogenase (PDC-E2), gp210, sp100 and CENP-A/B. Anti-PDC-E2 avidity was determined by 6 M urea-elution ELISA. Alkaline phosphatase (ALP), gamma glutamyl transferase (ɣGT) and ELF score were measured by automated methods.

Results

Along the follow-up period BN/AMA+ subjects and PBC patients presented significant increase in serum anti-PDC-E2 (mean 10.45% and 8.86% per year; respectively), anti-PDC-E2 avidity (3.02% and 4.94%/year) and ELF score (3.24% and 2.71%/year). IIF-AMA and ɣGT increased in BN/AMA+ (6.59% and 2.36%) and decreased in PBC (- 4.89%/year and - 3.88%/year). In BN/AMA+ individuals there was positive correlation of ELF with IIF-AMA titer (r = 0.465; p < 0.001) and with anti-PDC-E2 levels (r = 0.239; p < 0.001). Expansion of autoantibody targets along time occurred in 39% BN/AMA+ and 49% PBC patients. The frequency of BN/AMA+ with high probability of having established PBC increased from 7 to 14%.

Conclusions

BN/AMA+ individuals present an orchestrated increase in ELF score and humoral autoimmune response over time, indicating an opportunity for early therapeutic intervention and prevention in autoimmunity.

Immunological abnormalities in patients with primary biliary cholangitis

Primary biliary cholangitis (PBC), an autoimmune liver disease occurring predominantly in women, is characterized by high titers of serum anti-mitochondrial antibodies (AMAs) and progressive intrahepatic cholestasis. The immune system plays a critical role in PBC pathogenesis and a variety of immune cell subsets have been shown to infiltrate the portal tract areas of patients with PBC. Amongst the participating immune cells, CD4 T cells are important cytokine-producing cells that foster an inflammatory microenvironment. Specifically, these cells orchestrate activation of other immune cells, including autoreactive effector CD8 T cells that cause biliary epithelial cell (BEC) injury and B cells that produce large quantities of AMAs. Meanwhile, other immune cells, including dendritic cells (DCs), natural killer (NK) cells, NKT cells, monocytes, and macrophages are also important in PBC pathogenesis. Activation of these cells initiates and perpetuates bile duct damage in PBC patients, leading to intrahepatic cholestasis, hepatic damage, liver fibrosis, and eventually cirrhosis or even liver failure. Taken together, the body of accumulated clinical and experimental evidence has enhanced our understanding of the immunopathogenesis of PBC and suggests that immunotherapy may be a promising treatment option. Herein, we summarize current knowledge regarding immunological abnormalities of PBC patients, with emphasis on underlying pathogenic mechanisms. The differential immune response which occurs over decades of disease activity suggests that different therapies may be needed at different stages of disease.

Primary biliary cholangitis with contemporary presence of anti-mithocondrial and anti-rods and rings autoantibodies: literature first case

Primary biliary cholangitis, previously known as primary biliary cirrhosis (PBC), is the most common autoimmune diseases of the liver (ALD). Patients with PBC may present with typical biliary pattern symptoms. Also the presence of anti-mitochondrial autoantibodies (AMAs) is the laboratory hallmark of PBC, which molecular target antigens are members of 2-oxoacid dehydrogenase complex of enzymes. In recent years, autoantibodies (Aab) targeting subcellular structures described as the rods and rings (R&R) pattern in HEp-2 ANA have been presented as a unique and particular case of Aab generation. These R&R structures are composed of inosine monophosphate dehydrogenase type 2 (IMPDH2), and their formation can be induced in vitro by several small-molecule inhibitors. Aab targeting these relatively unknown structures have been almost exclusively observed in hepatitis C virus (HCV) patients who have undergone treatment with pegylated interferon-a/ribavirin (IFN/RBV) therapy. Literature showed that anti-RR Aab have not been found in no treatment-naïve HCV patients or in patients from any other disease. Now we present and characterized a case patient with contemporary presence of AMAs and R&R Aab in PBC, without any laboratory evidence of HCV and/or other hepatic virus infection. For our knowledge, this is the first case described in the Literature. R&R Aab in patients without any clinical/laboratory signs or symptoms of Hepatitis virus and without pharmacological therapy open the window to the alternative scenario: the association of these Aab to ALD. Our work demonstrated that R&R Aab can be present in PBC case. The interesting idea suggested that R&R Aab may be present also in AMA-negative PBC and they can considered a new possible diagnostic tool in this specific clinical condition. Other study and cases are needed but the presence of R&R Aab linked with AMAs and PBC may be explained by alterations in immune regulation caused by autoimmunity in a particular genetic background.

Biomarkers for primary biliary cholangitis: current perspectives

Primary biliary cholangitis (PBC) is a chronic progressive cholestatic disease characterized by destruction of small- and medium-sized intrahepatic bile ducts. It is no longer a rare disease, since many new asymptomatic cases are incidentally identified. Liver biopsy is diagnostically critical but not always feasible or practical to be performed. Many potential, noninvasive, markers have been proposed to replace liver biopsy and further provide the assessment of disease severity and ultimate prognosis. In this review, we evaluated serum biomarkers proposed for diagnosis, extent of fibrosis, disease prognosis and attempts for early prediction of treatment response. Older biochemical and immunological markers are presented along with recent reports including the role of microRNAs and promising results based on proteomics and metabolomics.

Evidence for the association between IgG-antimitochondrial antibody and biochemical response to ursodeoxycholic acid treatment in primary biliary cholangitis

BACKGROUND AND AIM

Antimitochondrial antibody (AMA) is considered the serological hallmark of primary biliary cholangitis (PBC), while data regarding the profile of AMA during ursodeoxycholic acid (UDCA) treatment are scarce. Here, we assessed the influence of UDCA treatment on titers of AMA and factors relevant to its production.

METHODS

Serum IgA-AMA, IgM-AMA, IgG-AMA, B cell-activating factor of the tumor necrosis factor family (BAFF), and the frequency of circulating plasmablasts were detected in PBC patients, including those who received UDCA therapy for 24 weeks, healthy controls, chronic hepatitis B patients, and autoimmune hepatitis patients. Consecutive liver sections from controls and PBC patients were stained by immunohistochemistry for detection of intrahepatic CD38⁺ , IgA⁺ , IgM⁺ , and IgG⁺ cells.

RESULTS

Significant decrease in titers of IgG-AMA was found only confined to PBC patients with biochemical response to UDCA treatment (P = 0.005), and similar pattern was also observed at week 24 in quantifying circulating plasmablasts (P = 0.025) and serum BAFF (P = 0.013). Notably, positive correlation between serum BAFF levels and titers of IgG-AMA, and the frequency of circulating plasmablasts were observed in PBC patients (r = 0.464, P = 0.034 and r = 0.700, P < 0.001, respectively). Additionally, in situ staining revealed significant accumulation of CD38⁺ and IgG⁺ cells within the portal tracts of PBC liver.

CONCLUSIONS

Decreased titers of serum IgG-AMA are associated with biochemical response to UDCA treatment, implicating the potentiality of this hallmark in therapeutic response evaluation and the beneficial effect of UDCA on humoral immunity in PBC patients.

A contemporary perspective on the molecular characteristics of mitochondrial autoantigens and diagnosis in primary biliary cholangitis

Primary biliary cholangitis (PBC) is an autoimmune hepatobiliary disease characterized by immune mediated destruction of the intrahepatic small bile ducts and the presence of antimitochondrial antibodies (AMAs). The mitochondrial autoantigens have been identified as the E2 subunits of the 2-oxo-acid dehydrogenase complex, including the E2 subunits of pyruvate dehydrogenase, branched-chain 2-oxo acid dehydrogenase complex, oxoglutarate dehydrogenase complex, E3 binding protein and PDC E1 alpha subunit. The AMA epitope is mapped within the E2 lipoic acid binding domain, which is particularly important for oxidative phosphorylation. In addition, lipoic acid, which serves as a swinging arm to capture electrons, is particularly susceptible to an electrophilic attack and may provide clues to the etiology of PBC. This review emphasizes the molecular characteristics of AMAs, including detection, immunochemistry and the putative role in disease. These data have significance not only specifically for PBC, but generically for autoimmunity.

The Significance of Autoantibody Changes Over Time in Primary Biliary Cirrhosis

OBJECTIVES

In primary biliary cirrhosis (PBC), the antimitochondrial antibody is a cornerstone of diagnosis, but there have been conflicting reports about the correlation of autoantibodies with disease stage and prognosis. We studied whether autoantibody levels changed over time and sought correlations with clinical outcomes in a cohort of patients with PBC.

METHODS

We tested serial serum samples from patients with PBC at a research institution for several autoantibodies. Long-term clinical follow-up data were used to calculate the slopes (change over time) for autoantibodies, platelet count, Ishak fibrosis score, biopsy copper, and number of portal areas with bile ducts. An adverse clinical outcome was defined as hepatic decompensation, development of hepatocellular carcinoma, liver transplantation, or liver-related death. We performed linear or logistic regression or Fisher exact test as appropriate, adjusting for multiple comparisons.

RESULTS

Twenty-seven patients with PBC with 145 serum samples were studied. Of the cohort, 85% was white, 81% was female, and median follow-up time was 20 years. Of the autoantibodies tested, only sp100 changed significantly over time. The sp100 slope was inversely associated with the Ishak fibrosis slope (parameter estimate, -0.05; P = .0003).

CONCLUSIONS

While changes in most autoantibodies over time do not seem to correlate with clinical outcomes in PBC, a change in the sp100 autoantibody level may have prognostic utility with respect to the development of fibrosis on liver biopsy.

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.

Role of the clinical immunology laboratory in disease monitoring

Immunological investigations provide useful information to guide diagnosis of several disorders. Many such tests are also commonly repeated at intervals, in an effort to facilitate disease monitoring. In general however, immunology test results are often slow to alter. Furthermore, audit activity has indicated that repeated testing accounts for a substantial workload in many immunology services, which may waste resources and compromise the efficient completion of necessary tests. Consequently, the need and appropriate minimum interval between repeated testing requires critical evaluation. In this review, the clinical utility of repeated performance of several common immunology investigations has been evaluated, based upon published evidence. In some cases (e.g., paraprotein quantification, or measurement of anti-glomerular basement membrane antibodies), repeated testing provides vital clinical information and can be justified on a frequent and individualized basis. However, many other investigations provided by immunology services provide less valuable information when used to aid disease monitoring rather than diagnosis. It is hoped that the data summarized here will facilitate a more evidence-based approach to repeated testing. Such information may also assist with the local implementation of demand management strategies based upon setting of minimum retesting intervals for these investigations.

Antimitochondrial antibody recognition and structural integrity of the inner lipoyl domain of the E2 subunit of pyruvate dehydrogenase complex

Antimitochondrial autoantibodies (AMAs), the serological hallmark of primary biliary cirrhosis, are directed against the lipoyl domain of the E2 subunit of pyruvate dehydrogenase (PDC-E2). However, comprehensive analysis of the amino acid residues of PDC-E2 lipoyl β-sheet with AMA specificity is lacking. In this study, we postulated that specific residues within the lipoyl domain are critical to AMA recognition by maintaining conformational integrity. We systematically replaced each of 19 residue peptides of the inner lipoyl domain with alanine and analyzed these mutants for reactivities against 60 primary biliary cirrhosis and 103 control sera. Based on these data, we then constructed mutants with two, three, or four replacements and, in addition, probed the structure of the substituted domains using thiol-specific spin labeling and electron paramagnetic resonance (EPR) of a (5)Ile→Ala and (12)Ile→Ala double mutant. Single alanine replacement at (5)Ile, (12)Ile, and (15)Glu significantly reduced AMA recognition. In addition, mutants with two, three, or four replacements at (5)Ile, (12)Ile, and (15)Glu reduced AMA reactivity even further. Indeed, EPR reveals a highly flexible structure within the (5)Ile and (12)Ile double-alanine mutant. Autoreactivity is largely focused on specific residues in the PDC-E2 lipoyl domain critical in maintaining the lipoyl loop conformation necessary for AMA recognition. Collectively, the AMA binding studies and EPR analysis demonstrate the necessity of the lipoyl β-sheet structural conformation in anti-PDC-E2 recognition.

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

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

Antimitochondrial antibody heterogeneity and the xenobiotic etiology of primary biliary cirrhosis

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

CONCLUSION

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

Molecular diagnostics of primary biliary cirrhosis

BACKGROUND

Primary biliary cirrhosis (PBC) is an autoimmune liver disease of unknown etiology characterized by the presence of antimitochondrial antibodies (AMA) in 90 - 95% of patients. AMA are directed against members of 2-oxo-acid dehydrogenase complex, including mainly the E2 subunit of pyruvate dehydrogenase, the E2 subunit of branched chain 2-oxo-acid dehydrogenase complex and the E2 subunit of the oxoglutarate dehydrogenase complex. Apart from AMA, PBC is characterized by the presence of PBC-specific antinuclear antibodies (ANA). The molecular targets of these PBC-specific ANA have been characterized as gp210, lamin B receptor, nucleoporin 62, sp100 and promyelocytic leukemia proteins.

OBJECTIVE

To discuss the molecular diagnostics of PBC in the context of AMA and PBC-specific ANA detection by the use of conventional and 'new' novel technologies.

METHODS

Critical analysis of all published data regarding PBC serology between 1985 and 2007 was performed in order to suggest a diagnostic algorithm for the serological diagnosis of PBC.

RESULTS/CONCLUSIONS

AMA are first detected by indirect immunofluorescence (IIF) on frozen sections of rat liver, kidney and stomach substrates. However, because IIF is time-consuming, labor-intensive and observer-dependent, molecular-based assays such as immunoblot and enzyme-linked immunosorbent assays have been developed with high sensitivity and specificity. Similarly, molecular-based assays have also been developed for the detection of PBC-specific ANA. The latter investigation seems to be of outmost importance because these autoantibodies can be used as a positive tool in the diagnosis of AMA-negative PBC while at the same time identifying a subgroup of PBC patients with more advanced disease. New test systems for the detection of PBC-specific antibodies based on the xMultiple Analyte Profiling Luminex methodology seems to be the future in molecular diagnostics of PBC as it was expected first to decrease the cost and second to speed up an accurate serological profile, although they may decrease further the proportion of AMA-negative PBC cases.

Impact of microbes on autoimmune diseases

Autoimmune and autoinflammatory diseases arise as a consequence of complex interactions of environmental factors with genetic traits. Although specific allelic variations cluster in predisposed individuals and promote the generation and/or expansion of autoreactive T and B lymphocytes, autoimmunity appears in various disease phenotypes and localizes to diverging tissues. Furthermore, the discovery that allelic variations within genes encoding components of the innate immune system drive self-reactive immune responses as well, led to the distinction of immune responses against host tissues into autoimmune and autoinflammatory diseases. In both categories of disorders, different pathogenic mechanisms and/or subsequent orders of tissue assaults may underlie the target cell specificity of the respective autoimmune attack. Furthermore, the transition from the initial tissue assault to the development of full-blown disease is likely driven by several factors. Thus, the development of specific forms of autoimmunity and autoinflammation reflects a multi-factorial process. The delineation of the specific factors involved in the pathogenic process is hampered by the fact that certain symptoms are assembled under the umbrella of a specific disease, although they might originate from diverging pathogenic pathways. These multi-factorial triggers and pathogenic pathways may also explain the inter-individual divergent courses and outcomes of diseases among humans. Here, we will discuss the impact of different environmental factors in general and microbial pathogens in particular on the regulation/expression of genes encoded within susceptibility alleles, and its consequences on subsequent autoimmune and/or autoinflammatory tissue damage utilizing primarily the chronic cholestatic liver disease primary biliary cirrhosis as model.

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

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

Role of autoimmunity in primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is an autoimmune liver disease characterized by the presence of serum autoantibodies and chronic nonsuppurative destructive cholangitis. The pathogenesis of PBC involves environmental factors, genetic predisposition and loss of immune tolerance. In recent years, it has become univocally accepted that an inappropriately activated immune response is one of the most important factors in PBC. In this study, the role of autoimmunity in PBC is summarized and a feasible research orientation is recommended.

Xenobiotics and autoimmunity: does acetaminophen cause primary biliary cirrhosis?

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

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.

Electrophile-modified lipoic derivatives of PDC-E2 elicits anti-mitochondrial antibody reactivity

Our laboratory has hypothesized that xenobiotic modification of the native lipoyl moiety of the major mitochondrial autoantigen, the E2 subunit of the pyruvate dehydrogenase complex (PDC-E2), may lead to loss of self-tolerance in primary biliary cirrhosis (PBC). This thesis is based on the finding of readily detectable levels of immunoreactivity of PBC sera against extensive panels of protein microarrays containing mimics of the inner lipoyl domain of PDC-E2 and subsequent quantitative structure-activity relationships (QSARs). Importantly, we have demonstrated that murine immunization with one such mimic, 2-octynoic acid coupled to bovine serum albumin (BSA), induces anti-mitochondrial antibodies (AMAs) and cholangitis. Based upon these data, we have focused on covalent modifications of the lipoic acid disulfide ring and subsequent analysis of such xenobiotics coupled to a 15mer of PDC-E2 for immunoreactivity against a broad panel of sera from patients with PBC and controls. Our results demonstrate that AMA-positive PBC sera demonstrate marked reactivity against 6,8-bis(acetylthio)octanoic acid, implying that chemical modification of the lipoyl ring, i.e. disruption of the S-S disulfide, renders lipoic acid to its reduced form that will promote xenobiotic modification. This observation is particularly significant in light of the function of the lipoyl moiety in electron transport of which the catalytic disulfide constantly opens and closes and, thus, raises the intriguing thesis that common electrophilic agents, i.e. acetaminophen or non-steroidal anti-inflammatory drugs (NSAIDs), may lead to xenobiotic modification in genetically susceptible individuals that results in the generation of AMAs and ultimately clinical PBC.

Autoantibodies to GW bodies and other autoantigens in primary biliary cirrhosis

Autoantibodies to intracellular targets in mitochondria and nuclei are serological hallmarks of primary biliary cirrhosis (PBC). One of the most recently identified cellular targets of PBC autoantibodies is a novel cytoplasmic structure referred to as GW bodies [GWB, G (glycine) W (tryptophan)-containing bodies (GWB)]. GWB are indentified as discrete cytoplasmic domains that are involved in mRNA processing via the RNA interference (RNAi) pathway. Key components of GWB include the proteins GW182, Ago2, RNA-associated protein 55 (RAP55) and Ge-1/Hedls. The primary objective was to study the frequency and clinical association of antibodies directed to GWB components, in 109 PBC patients. Autoantibodies to mitochondrial antigen-pyruvate dehydrogenase complex (M2), branched-chain 2-oxo-acid dehydrogenase complex and 2-oxo glutarate dehydrogenase complex (3E-BPO), gp210, sp100, promyelocytic leukaemia cell antigen (PML) and liver kidney microsomal-1 antigen (LKM-1) were detected by a line immunoassay and antibodies to GWB (GW182, RAP55, Ge-1, GW2, GW3) and glutamate receptor interacting protein (GRIP)-associated protein-1 (GRASP-1), by an addressable laser bead immunoassay (ALBIA). The most common GWB autoantigen targets were: RAP55-28%, GW182-12%, GW2-2% and antibodies to GRASP-1-17%. By comparison, the frequency of reactivity to established PBC autoantigens was: gp210, 27%; sp100, 27% and PML, 17%. None of the autoantibodies were associated with differences in Mayo risk score or liver decompensation. This study is the first study to show that antibodies to RAP55, GW182 and GRASP-1 are the most common GWB targets in PBC.

Biliary epithelial apoptosis, autophagy, and senescence in primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is a chronic cholestatic liver disease characterized serologically by the high prevalence of anti-mitochondrial autoantibodies (AMAs) and histologically by the cholangitis of small bile ducts, eventually followed by extensive loss of the small bile duct. An autoimmune pathogenesis is suggested by clinical and experimental studies, but there remain issues regarding the etiology, the significance of AMAs in the pathogenesis of bile duct lesions, and so on. The unique properties of apoptosis in biliary epithelial cells (BECs), in which there is exposure of autoantigen to the effectors of the immune system, are proposed to be a cause of bile duct lesions in PBC. Recent progress disclosed that cellular senescence and autophagy are involved in bile duct lesions in PBC. Senescent BECs may modulate the periductal microenvironment by expressing senescence-associated secretory phenotypes, including various chemokines, and contribute to the pathogenesis of bile duct lesions in PBC.

Primary biliary cirrhosis: What do autoantibodies tell us?

Primary biliary cirrhosis (PBC) is a chronic, progressive, cholestatic, organ-specific autoimmune disease of unknown etiology. It predominantly affects middle-aged women, and is characterized by autoimmune-mediated destruction of small- and medium-size intrahepatic bile ducts, portal inflammation and progressive scarring, which without proper treatment can ultimately lead to fibrosis and hepatic failure. Serum autoantibodies are crucial tools for differential diagnosis of PBC. While it is currently accepted that antimitochondrial antibodies are the most important serological markers of PBC, during the last five decades more than sixty autoantibodies have been explored in these patients, some of which had previously been thought to be specific for other autoimmune diseases.

Experimental evidence on the immunopathogenesis of primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is a chronic cholestatic liver disease for which an autoimmune pathogenesis is supported by clinical and experimental data, including the presence of autoantibodies and autoreactive T cells. The etiology remains to be determined, yet data suggest that both a susceptible genetic background and unknown environmental factors determine disease onset. Multiple infectious and chemical candidates have been proposed to trigger the disease in a genetically susceptible host, mostly by molecular mimicry. Most recently, several murine models have been reported, including genetically determined models as well as models induced by immunization with xenobiotics and bacteria.

A comprehensive evaluation of serum autoantibodies in primary biliary cirrhosis

In primary biliary cirrhosis (PBC) serum markers other than anti-mitochondrial antibodies (AMA) are promising in terms of disease severity and comorbidities, as well represented by anti-nuclear antibodies (ANA). The aim of the present study was thus to evaluate the prevalence and clinical significance of a large profile of serum autoantibodies in PBC sera. We utilized 69 sera from European patients with PBC (including 20 AMA-negative) and 297 sera from geographically and sex-matched healthy controls. All sera were tested for the presence of ANA and autoantibodies associated with thrombophilia, vasculitis, and gastrointestinal disease. Autoantibodies other than AMA were detected in 53/69 (76%) PBC sera vs. 105/297 (35%) among controls. The prevalence of ANA (targeting dsDNA, Sm, chromatin, ribosomal-P, RNP, SmRNP, SSA, SSB, and centromere) and thrombophilia-associated autoantibodies (i.e. anti-beta2GPI, phosphatydilserine, prothrombin) was common among patients with PBC. When clinical features were compared, the presence of anti-prothrombin IgM was associated with a worse prognosis as represented by a higher Mayo score. We demonstrate an increased prevalence of ANA and thrombophilia-associated autoantibodies in PBC sera and an association between the latter autoantibodies and PBC stage. The role of thrombophilia-associated antibodies will warrant further studies, based in particular on the incidence of portal hypertension at early stages of PBC.

The role of environmental factors in primary biliary cirrhosis

The etiology of primary biliary cirrhosis (PBC) is enigmatic, although it is clearly related to a combination of genetic predisposition and environmental stimulation. PBC is a chronic autoimmune cholestatic liver disease that occurs throughout the world with a reported latitudinal gradient in prevalence and incidence. PBC is also characterized by a 60% concordance in monozygotic twins and is considered a model autoimmune disease because of several features common to other conditions and the relatively homogeneous serological and biochemical features. Several risk factors have been suggested to be associated with PBC, including exposure to infectious agents and chemical xenobiotics. This review will attempt to place such factors in perspective.

Ursodeoxycholic acid reduces CpG-induced IgM production in patients with primary biliary cirrhosis

AIM

Ursodeoxycholic acid (UDCA) treatment reduces IgM serum levels in patients with primary biliary cirrhosis (PBC) without affecting serum antimitochondrial antibody (AMA) titers. We previously reported that PBC-associated hyper-IgM is secondary to a disease-specific hyperproduction following bacterial stimulation by B cells.

METHODS

We isolated peripheral blood mononuclear cells (PBMC) from patients with PBC and controls and evaluated whether bacterial CpG challenge in the presence of UDCA at concentrations consistent with those achieved in treated patients led to changes in total IgM, IgG-AMA, and IgM-AMA production. Further, p65 phosphorylation and CD38 cell expression were analyzed as measures of activation of the NF-kB signaling pathway and B cell subsets, respectively.

RESULTS

UDCA significantly reduced CpG-induced total IgM and IgM-AMA production, but had no impact on IgG-AMA production. UDCA also significantly reduced the activation ofnaïve and IgM memory, but not IgG memory, B cells, as represented by CD38 expression levels. Further, p65 phosphorylation was significantly reduced in the presence of UDCA.

CONCLUSION

UDCA reduces total and IgM-AMA production in PBMC from patients with PBC by downregulating B cell activation and NF-kB signaling. These data ultimately suggest novel mechanisms of action for UDCA in chronic autoimmune cholestasis.

Anti-mitochondrial antibody-negative primary biliary cirrhosis

The recent development in the authors' laboratory of a sensitive bead assay able to detect AMA in 20% of otherwise AMA-negative sera seems to support the hypothesis that many AMA-negative cases of primary biliary cirrhosis (PCB) are secondary to limits in the methods used and do not represent an independent clinical entity. Clinical data demonstrate that patients without detectable serum AMA do not differ in their natural history from their seropositive counterparts. Anti-nuclear antibodies have been associated repeatedly with more severe disease and are helpful tools in the management of patients who have PBC, particularly those lacking AMA.

Concept on the pathogenesis and treatment of primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is an organ-specific autoimmune disease that predominantly affects women and is characterized by chronic, progressive destruction of small intrahepatic bile ducts with portal inflammation and ultimately fibrosis, leading to liver failure in the absence of treatment. Little is known about the etiology of PBC. PBC is characterized by anti-mitochondrial antibodies and destruction of intra-hepatic bile ducts. The serologic hallmark of PBC is the presence of auto-antibodies to mitochondria, especially to the E2 component of the pyruvate dehydrogenase complex (PDC). Current theories on the pathogenesis of PBC favor the hypothesis that the disease develops as a result of an inappropriate immune response following stimulation by an environmental or infectious agent. Some reports suggest that xenobiotics and viral infections may induce PBC. The pathogenetic mechanism is believed to be caused by a defect in immunologic tolerance, resulting in the activation and expansion of self-antigen specific T and B lymphocyte clones and the production of circulating autoantibodies in addition to a myriad of cytokines and other inflammatory mediators. This leads to ductulopenia and persistent cholestasis, by developing end-stage hepatic-cell failure. In this review are given our own and literary data about mechanisms of development of intrahepatic cholestasis and possible ways of its correction.

Antinuclear antibodies giving the 'multiple nuclear dots' or the 'rim-like/membranous' patterns: diagnostic accuracy for primary biliary cirrhosis

BACKGROUND

Serum antinuclear antibodies giving the 'multiple nuclear dots' or the 'rim-like/membranous' patterns are frequently detected by indirect immunofluorescence on HEp-2 cells in patients with primary biliary cirrhosis.

AIM

To assess the accuracy of multiple nuclear dot and rim-like/membranous antinuclear antibodies for the diagnosis of primary biliary cirrhosis.

METHODS

Sera from 4371 consecutive patients referred to our laboratory were analysed under code for antinuclear antibodies testing by indirect immunofluorescence on HEp-2 cells.

RESULTS

Review of the clinical records of the 4371 patients allowed identification of 101 patients with antimitochondrial antibody-positive primary biliary cirrhosis and 22 with antimitochondrial antibody-negative variant. Multiple nuclear dot and/or rim-like/membranous patterns were found in 59 (1.3%) of the 4371 patients: 31 antimitochondrial antibody-positive primary biliary cirrhosis, 17 antimitochondrial antibody-negative primary biliary cirrhosis and 11 non-primary biliary cirrhosis. The specificity for primary biliary cirrhosis of both the antinuclear antibodies pattern was 99%. Positive predictive value and likelihood ratio for a positive test were 86% (95% CI: 72.7-94) and 221 (95% CI: 91.7-544) for multiple nuclear dot, 79% (95% CI: 62.2-90.1) and 132 (95% CI: 56.8-312.7) for rim-like/membranous, respectively.

CONCLUSIONS

Multiple nuclear dot and rim-like/membranous antinuclear antibodies are rare findings. Their positivity strongly suggests the diagnosis of primary biliary cirrhosis, irrespective of antimitochondrial antibody status. The high specificity for primary biliary cirrhosis makes them a useful diagnostic tool especially in antimitochondrial antibody-negative patients.

IL-2 receptor alpha(-/-) mice and the development of primary biliary cirrhosis

Recently, we identified a child born with a genetic deficiency of IL-2 receptor alpha (IL-2Ralpha, CD25) expression who had several clinical manifestations of primary biliary cirrhosis (PBC). In addition, there has been suggestive evidence in both patients with PBC and their first-degree relatives that a deficiency of regulatory T cells (Tregs) is an integral component for susceptibility to PBC. Based on these observations, we generated IL-2Ralpha/CD25 deficient (IL-2Ralpha(-/-)) mice and wild-type littermate controls and followed them longitudinally for the natural history of liver immunopathology and appearance of antimitochondrial antibodies (AMAs). The analyses included immunohistochemical staining of liver and portal tract infiltrates as well as FACS profiles of lymphoid subpopulations in liver and spleen. In addition, serum cytokine profiles were quantitated. Importantly, IL-2Ralpha(-/-), but not littermate controls, develop portal inflammation and biliary ductular damage similar to human patients with PBC. CD4(+) and CD8(+) T cells predominate among portal cell infiltrates and sera reflect a Th1 cytokine bias with increased levels of IFN-gamma, TNF-alpha, IL-2 and IL-12p40. Of importance is the finding that the IL-2Ralpha(-/-) mice not only develop significantly increased serum levels of IgG and IgA, but they also develop AMAs with specificity for PDC-E2, which maps to the inner lipoyl domain of the autoantigen, all characteristics which are hallmarks of human PBC. In conclusion, the IL-2Ralpha(-/-) mice should facilitate studies of the early events in PBC and especially the tantalizing connection between Treg deficiency and autoimmunity specifically directed to mitochondrially located PDC-E2 and subsequent biliary ductular cell damage.

Long-lived plasma cells and their contribution to autoimmunity

The current view holds that chronic autoimmune diseases are driven by the continuous activation of autoreactive B and T lymphocytes. However, despite the use of potent immunosuppressants, the production of autoantibodies may persist and contribute to the autoimmune pathology. We recently demonstrated in autoimmune mice that both short-lived plasmablasts and long-lived plasma cells are involved in autoantibody production. While anti-proliferative immunosuppressive therapy and monoclonal anti-CD20 antibody deplete short-lived plasmablasts, long-lived plasma cells survive and continue to produce (auto)antibodies. Thus, strategies for targeting long-lived plasma cells may provide potent new treatment modalities.