Autoantigens in primary biliary cirrhosis

Increased type-I interferon level is associated with liver damage and fibrosis in primary sclerosing cholangitis

BACKGROUND

The level of type-I interferons (IFNs) in primary sclerosing cholangitis (PSC) was investigated to evaluate its association with disease activity and progression.

METHODS

Bioactive type-I IFNs were evaluated in a murine model of PSC and human patients' sera using a cell-based reporter assay and ELISA techniques. In total, 57 healthy participants, 71 PSC, and 38 patients with primary biliary cholangitis were enrolled in this study.

RESULTS

Bioactive type-I IFNs were elevated in the liver and serum of multidrug resistance protein 2-deficient animals and showed a correlation with the presence of CD45+ immune cells and serum alanine transaminase levels. Concordantly, bioactive type-I IFNs were elevated in the sera of patients with PSC as compared to healthy controls (sensitivity of 84.51%, specificity of 63.16%, and AUROC value of 0.8267). Bioactive IFNs highly correlated with alkaline phosphatase (r=0.4179, p<0.001), alanine transaminase (r=0.4704, p<0.0001), and gamma-glutamyl transpeptidase activities (r=0.6629, p<0.0001) but not with serum bilirubin. In addition, patients with PSC with advanced fibrosis demonstrated significantly higher type-I IFN values. Among the type-I IFN subtypes IFNα, β and IFNω could be detected in patients with PSC with IFNω showing the highest concentration among the subtypes and being the most abundant among patients with PSC.

CONCLUSIONS

The selectively elevated bioactive type-I IFNs specifically the dominating IFNω could suggest a novel inflammatory pathway that might also have a hitherto unrecognized role in the pathomechanism of PSC.

Immunomodulatory role of mitochondrial DAMPs: a missing link in pathology?

In accordance with the endosymbiotic theory, mitochondrial components bear characteristic prokaryotic signatures, which act as immunomodulatory molecules when released into the extramitochondrial compartment. These endogenous immune triggers, called mitochondrial damage-associated molecular patterns (mtDAMPs), have been implicated in the pathogenesis of various diseases, yet their role remains largely unexplored. In this review, we summarise the available literature on mtDAMPs in diseases, with a special focus on respiratory diseases. We highlight the need to bolster mtDAMP research using a multipronged approach, to study their effect on specific cell types, receptors and machinery in pathologies. We emphasise the lacunae in the current understanding of mtDAMPs, particularly in their cellular release and the chemical modifications they undergo. Finally, we conclude by proposing additional effects of mtDAMPs in diseases, specifically their role in modulating the immune system.

Immune checkpoint inhibitor-related cholangiopathy: Novel clinicopathological description of a multi-centre cohort

BACKGROUND AND AIMS

Cholestatic liver dysfunction is common in immune-related hepatitis (irH) during treatment with immune checkpoint inhibitors (CPI) for malignancy. We investigated the spectrum of bile duct injury and associated natural history in this cohort.

METHOD

Clinical, laboratory, radiological and histopathological data in patients with evidence of bile duct injury during CPI treatment from 2018 to 2020 was collected in three tertiary hospitals.

RESULTS

In this study, ten patients with confirmed bile duct disease were identified. Pembrolizumab was most commonly implicated (8/10). Median CPI cycles prior to bile duct injury was 6. Median alanine aminotransferase and alkaline phosphatase were 225 U/L and 1549 U/L respectively. Clinical jaundice was seen in 6/10 and radiological evidence of bile duct pathology in 8/10. Of five patients, who had liver biopsy, three cases (including two cases with normal MRCP) showed primary sclerosing cholangitis (PSC) like changes with periductal fibrosis. All patients were treated first-line with prednisolone following cessation of CPI, three with mycophenolate mofetil and one with tacrolimus, with clinical response in four patients. Five patients died after a mean follow-up of 27 weeks; cause of death was primarily related to progression of malignancy.

CONCLUSION

Within this heterogeneous cohort, we identified that CPI-related cholangiopathy responded poorly to immunosuppression and potentially progressed to bile duct loss. Thorough radiological and histological assessment is recommended, as identification of the cholangiopathy-associated phenotype may permit more informed advice regarding prognosis. Further data is required to determine detailed immunological characterisation in order to identify individuals at an increased risk of developing cholangiopathy.

Prediction of Immune-Related Adverse Events Induced by Immune Checkpoint Inhibitors With a Panel of Autoantibodies: Protocol of a Multicenter, Prospective, Observational Cohort Study

Introduction: Immune checkpoint inhibitor (ICI) therapy is markedly improving the prognosis of patients with several types of cancer. On the other hand, the growth in the use of these drugs in oncology is associated with an increase in multiple immune-related adverse events (irAEs), whose optimal prevention and management remain unclear. In this context, there is a need for reliable and validated biomarkers to predict the occurrence of irAEs in patients treated with ICIs. Thus, the main objective of this study is to evaluate the diagnostic performance of a sensitive routinely available panel of autoantibodies consisting of antinuclear antibodies, rheumatoid factor, and antineutrophil cytoplasmic antibodies to identify patients at risk of developing irAEs.

Methods and Analysis: A multicenter, prospective, observational, cohort study has been designed to be conducted in patients diagnosed with cancer amenable to ICI therapy. Considering the percentage of ICI-induced irAEs to be 25% and a loss to follow-up of 5%, it has been estimated that a sample size of 294 patients is required to detect an expected sensitivity of the autoantibody panel under study of 0.90 with a confidence interval (95%) of no less than 0.75. For 48 weeks, patients will be monitored through the oncology outpatient clinics of five hospitals in Spain. Immune-related adverse events will be defined and categorized according to CTCAE v. 5.0. All the patients will undergo ordinary blood tests at specific moments predefined per protocol and extraordinary blood tests at the time of any irAE being detected. Ordinary and extraordinary samples will be frozen and stored in the biobank until analysis in the same autoimmunity laboratory when the whole cohort reaches week 48. A predictive model of irAEs will be constructed with potential risk factors of immune-related toxicity including the autoantibody panel under study.

Ethics and Dissemination: This protocol was reviewed and approved by the Ethical Committee of the Basque Country and the Spanish Agency of Medicines and Medical Devices. Informed consent will be obtained from all participants before their enrollment. The authors declare that the results will be submitted to an international peer-reviewed journal for their prompt dissemination.

Antibody-Mediated Rejection and Recurrent Primary Disease: Two Main Obstacles in Abdominal Kidney, Liver, and Pancreas Transplants

The advances in acute phase care have firmly established the practice of organ transplantation in the last several decades. Then, the next issues that loom large in the field of transplantation include antibody-mediated rejection (ABMR) and recurrent primary disease. Acute ABMR is a daunting hurdle in the performance of organ transplantation. The recent progress in desensitization and preoperative monitoring of donor-specific antibodies enables us to increase positive outcomes. However, chronic active ABMR is one of the most significant problems we currently face. On the other hand, recurrent primary disease is problematic for many recipients. Notably, some recipients, unfortunately, lost their vital organs due to this recurrence. Although some progress has been achieved in these two areas, many other factors remain largely obscure. In this review, these two topics will be discussed in light of recent discoveries.

Investigation of immune complexes formed by mitochondrial antigens containing a new lipoylated site in sera of primary biliary cholangitis patients

Primary biliary cholangitis (PBC) is characterized by the presence of serum anti-mitochondrial autoantibodies (AMAs). To date, four antigens among the 2-oxo-acid dehydrogenase complex family, which commonly have lipoyl domains as an epitope, have been identified as AMA-corresponding antigens (AMA-antigens). It has recently been reported that AMAs react more strongly with certain chemically modified mimics than with the native lipoyl domains in AMA-antigens. Moreover, high concentrations of circulating immune complexes (ICs) in PBC patients have been reported. However, the existence of ICs formed by AMAs and their antigens has not been reported to date. We hypothesized that AMAs and their antigens formed ICs in PBC sera, and analyzed sera of PBC and four autoimmune diseases (Sjögren's syndrome, systemic lupus erythematosus, systemic scleroderma, and rheumatoid arthritis) using immune complexome analysis, in which ICs are separated from serum and are identified by nano-liquid chromatography-tandem mass spectrometry. To correctly assign MS/MS spectra to peptide sequences, we used a protein-search algorithm that including lipoylation and certain xenobiotic modifications. We found three AMA-antigens, the E2 subunit of the pyruvate dehydrogenase complex (PDC-E2), the E2 subunit of the 2-oxo-glutarate dehydrogenase complex (OGDC-E2) and dihydrolipoamide dehydrogenase binding protein (E3BP), by detecting peptides containing lipoylation and xenobiotic modifications from PBC sera. Although the lipoylated sites of these peptides were different from the well-known sites, abnormal lipoylation and xenobiotic modification may lead to production of AMAs and the formation ICs. Further investigation of the lipoylated sites, xenobiotic modifications, and IC formation will lead to deepen our understanding of PBC pathogenesis.

Prevalence of antimitochondrial antibodies in subacute cutaneous lupus erythematosus

BACKGROUND

In approximately 13% of systemic lupus erythematosus (SLE) patients, a hallmark of primary biliary cirrhosis (PBC) can be detected: antimitochondrial M2 antibodies (AMA-M2). It has not been determined if the presence of AMA-M2 in SLE patients results in a higher risk of PBC in comparison to those with AMA but no SLE. Until now, there have been no such analyses among individuals with subacute cutaneous lupus erythematosus (SCLE).

METHODS

To assess the seropositivity rates for AMA-M2 and autoantibodies associated with autoimmune hepatitis in patients with newly diagnosed SCLE and to determine the coexistence and risk of development of autoimmune liver disease in these patients within 1 year of follow-up, data from 33 patients with newly diagnosed SCLE were analyzed.

RESULTS

AMA-M2 was found in 20% of SCLE patients. Patients from the AMA-M2-positive group were characterized by significantly higher levels of cholestatic liver enzymes when compared to those without AMA-M2 (P < 0.05). After introducing therapy with hydroxychloroquine and prednisone, the levels of hepatocellular enzymes increased significantly only in AMA-M2 positive patients (P < 0.05).

CONCLUSIONS

A high prevalence of AMA-M2 was found in patients with SCLE. Patients with SCLE and AMA-M2 had significantly higher values of cholestatic enzymes than patients without AMA. Newly diagnosed patients with SCLE should be screened for the presence of AMA and should be clinically followed up. Avoiding drugs with potential liver toxicity should be recommended in patients with SCLE and AMA.

Autoantibodies 2015: From diagnostic biomarkers toward prediction, prognosis and prevention

At the 12th International Workshop on Autoantibodies and Autoimmunity (IWAA), organized in August 2014 in Sao Paulo, Brazil, more than 300 autoimmunologists gathered to discuss the status of many novel autoantibodies in clinical practice, and to envisage additional value of autoantibodies in terms of prediction, prognosis and prevention of autoimmune diseases. Two separate workshops were dedicated to standardization and harmonization of autoantibody testing and nomenclature: International Autoantibody Standardization (IAS) and International Consensus on ANA Patterns (ICAP). It was apparent to all in attendance that the discovery and elucidation of novel autoantibodies did not slow down, but that multiple challenges lay ahead of us in order to apply these discoveries to effective and efficient clinical practice. Importantly, this requires optimal bidirectional communication between clinicians and laboratory specialists, as well as close collaboration with the diagnostic industry. This paper is a report on the 12th IWAA in combination with a review of the recent developments in the field of autoantibodies.

Association of Primary Biliary Cirrhosis-autoimmune Hepatitis Overlap Syndrome with Immune Thrombocytopenia and Graves' Disease

A 54-year-old woman suffering from pruritus for five years was diagnosed to have Graves' disease and immune thrombocytopenia (ITP) associated with primary biliary cirrhosis (PBC)-autoimmune hepatitis (AIH) overlap syndrome, which was confirmed histologically after a prompt recovery in the platelet count number following steroid therapy. The association between PBC-AIH overlap syndrome and ITP has been rarely reported and the additional association with Graves' disease has not yet been reported. An underlying global derangement of autoimmunity or shared genetic susceptibility was suspected.

Towards a liquid self: how time, geography, and life experiences reshape the biological identity

The conceptualization of immunological self is amongst the most important theories of modern biology, representing a sort of theoretical guideline for experimental immunologists, in order to understand how host constituents are ignored by the immune system (IS). A consistent advancement in this field has been represented by the danger/damage theory and its subsequent refinements, which at present represents the most comprehensive conceptualization of immunological self. Here, we present the new hypothesis of "liquid self," which integrates and extends the danger/damage theory. The main novelty of the liquid self hypothesis lies in the full integration of the immune response mechanisms into the host body's ecosystems, i.e., in adding the temporal, as well as the geographical/evolutionary and environmental, dimensions, which we suggested to call "immunological biography." Our hypothesis takes into account the important biological changes occurring with time (age) in the IS (including immunosenescence and inflammaging), as well as changes in the organismal context related to nutrition, lifestyle, and geography (populations). We argue that such temporal and geographical dimensions impinge upon, and continuously reshape, the antigenicity of physical entities (molecules, cells, bacteria, viruses), making them switching between "self" and "non-self" states in a dynamical, "liquid" fashion. Particular attention is devoted to oral tolerance and gut microbiota, as well as to a new potential source of unexpected self epitopes produced by proteasome splicing. Finally, our framework allows the set up of a variety of testable predictions, the most straightforward suggesting that the immune responses to defined molecules representing potentials antigens will be quantitatively and qualitatively quite different according to the immuno-biographical background of the host.

Involvement of commensal bacteria may lead to dysregulated inflammatory and autoimmune responses in a mouse model for chronic nonsuppurative destructive cholangitis

BACKGROUND

We previously reported a mouse model of primary biliary cirrhosis (PBC)-like chronic nonsuppurative destructive cholangitis (CNSDC), in which frequent injections of Streptococcus intermedius induced CNSDC and autoantibody production. The present study was performed to verify the model by examining 1) the reappearance of the PBC-like CNSDC after lymphocyte transfer from model to naïve mice, 2) the involvement of autophagy, and 3) the influence of the strain difference.

METHODS

Mice were inoculated with S. intermedius weekly for 8 weeks, then sacrificed to obtain samples. Spleen cells obtained from S. intermedius-inoculated mice were transferred to RAG2(-/-) mice.

RESULTS

CNSDC and elevated serum level of anti-gp210 titers were observed in S. intermedius-inoculated C57BL/6 mice, similar to the results of our previous report using BALB/c mice. Portal inflammation was induced in the livers of RAG2(-/-) mice by the transfer of spleen cells from S. intermedius-inoculated C57BL/6 mice. Among the inflammatory cells in the RAG2(-/-) mice, CD3-positive cells were predominant. Autophagosome-like structures were detected histologically, in the cytoplasm of infiltrated cells around the bile ducts in the livers of S. intermedius-inoculated both C57BL/6 and BALB/c mice. In S. intermedius-inoculated C3H/HeJ mice, inflammation in the portal area was less extensive than that in the hepatic parenchyma.

CONCLUSION

Bacterial component(s) and sequentially upregulated innate and acquired immune responses, accompanied by autophagy, might trigger CNSDC, via autoimmune mechanisms. Throughout the generation of bacteria-triggered PBC-like CNSDC, strain difference may influence the response to S. intermedius-inoculation in the liver.

Emerging role of damage-associated molecular patterns derived from mitochondria in inflammation

Cell death and injury often lead to release or exposure of intracellular molecules called damage-associated molecular patterns (DAMPs) or cell death-associated molecules. These molecules are recognized by the innate immune system by pattern recognition receptors - the same receptors that detect pathogen-associated molecular patterns, thus revealing similarities between pathogen-induced and non-infectious inflammatory responses. Many DAMPs are derived from the plasma membrane, nucleus, endoplasmic reticulum and cytosol. Recently, mitochondria have emerged as other organelles that function as a source of DAMPs. Here, we highlight the significance of mitochondrial DAMPs and discuss their contribution to inflammation and development of human pathologies.

Critical flicker frequency fails to disclose brain dysfunction in patients with primary biliary cirrhosis

BACKGROUND

Recent studies suggest that stage-independent symptoms of primary biliary cirrhosis (PBC) such as chronic fatigue are a consequence of structural and functional abnormalities of the brain. Critical flicker frequency (CFF) is a psychophysiological modality analysing function of cerebral cortex.

AIM

To analyse the usefulness of CFF in detection of brain dysfunction in patients with PBC.

METHODS

Fifty-one (37 non-cirrhotic/14 cirrhotic) patients with PBC were included. Control group consisted of 31 matched healthy individuals. Fatigue and health-related quality of life (HRQoL) were assessed using Fatigue Impact Scale (FIS) and questionnaire PBC-40. CFF was analysed with HEPAtonorm Analyzer(®).

RESULTS

When compared to healthy controls all patients with PBC showed significantly impaired HRQoL in majority of PBC-40 domains and increased fatigue level in physical domain of FIS. No differences in HRQoL and PBC-40 domains were seen, when patients with and without cirrhosis where compared. CFF analysis showed no difference between healthy controls and patients with PBC. CFF did not correlate with PBC-40 and FIS domains.

CONCLUSION

CFF fails to determine brain dysfunction in non-encephalopatic patients with PBC, suggesting that functional efficiency of their cerebral cortex remains unaffected and other central mechanisms are responsible for chronic fatigue in these patients.

Resistance to activation-induced cell death and elevated FLIPL expression of CD4+ T cells in a polyI:C-induced primary biliary cirrhosis mouse model

Primary biliary cirrhosis (PBC) is a type of organ-specific autoimmune disease in which immune tolerance is impaired by an unknown mechanism. We established a PBC animal model by injecting C57BL/6 mice with polyI:C to study activation-induced cell death (AICD) in CD4+ T lymphocytes and changes of apoptosis-associated molecules as a first step to understand the immune tolerance of PBC mice. Obvious inflammatory cell infiltration was observed in the portal area of the liver tissues in model mice and antimitochondrial antibodies (AMA) positive rate was 80%. The AICD level in both splenic and hepatic CD4+ T cells in the model group were all lower than those in controls, and in the model group the level for hepatic CD4+ T cells were significantly lower than that for splenic CD4+ T cells. Quantitative PCR revealed that FasL mRNA and TRAIL expression in CD4+ T cells in the model group decreased significantly compared with that in the control group. Western blots revealed that the expression of the anti-apoptotic protein FLIP(L) in the model group increased significantly with the FLIP(L) expression in hepatic CD4+ T cells significantly higher than that in splenic CD4+ T cells. There was a positive linear correlation between the number of infiltrated portal areas and relative expression of FLIP(L) in splenic CD4+ T cells in model group. There were no obvious changes for caspase-8 in either group. These results show that the anti-apoptotic ability of CD4+ T lymphocytes play an important role in immune tolerance in the PBC mouse model, and elevated FLIP(L) expression may enhance this ability. The inhibition of FasL and TRAIL expression may also help enhance this anti-apoptotic ability in CD4+ T lymphocytes and contribute to the aggravation of portal area inflammation.

Fatigue in primary biliary cirrhosis

The autoimmune liver disease, primary biliary cirrhosis (PBC), is associated with debilitating fatigue in a significant proportion of patients. The pathogenesis of fatigue in PBC is unclear, but preliminary studies suggest it has central mechanisms and may have peripheral manifestations. Studies are beginning to elucidate the biological associates of fatigue in PBC, particularly sleep disturbance and autonomic dysfunction. Comprehensive studies investigating the pathogenesis of fatigue in PBC are urgently needed as are large-scale prospective outcome studies.

Drug-induced hepatitis superimposed on the presence of anti-SLA antibody: a case report

Introduction

Autoimmune hepatitis is a necroinflammatory disorder of unknown etiology characterized by the presence of circulating antibodies, hypergammaglobulinemia, and response to immunosuppression. It has the histological features of chronic hepatitis. The onset is usually insidious, but in some patients the presentation may be acute and occasionally severe. Certain drugs can induce chronic hepatitis mimicking autoimmune hepatitis. Different autoantibodies have been associated with this process but they are not detectable after drug withdrawal and clinical resolution.

Case presentation

We describe a case of drug-induced acute hepatitis associated with antinuclear, antisoluble liver-pancreas and anti-smooth muscle autoantibodies in a 66-year-old woman. Abnormal clinical and biochemical parameters resolved after drug withdrawal, but six months later anti-soluble liver-pancreas antibodies remained positive and liver biopsy showed chronic hepatitis and septal fibrosis. Furthermore, our patient has a HLA genotype associated with autoimmune hepatitis.

Conclusion

Patient follow-up will disclose whether our patient suffers from an autoimmune disease and if the presence of anti-soluble liver antigens could precede the development of an autoimmune hepatitis, as the presence of antimitochondrial antibodies can precede primary biliary cirrhosis.

Measurement of gp210 autoantibodies in sera of patients with primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is an autoimmune liver disease with unknown etiology. Patients with PBC have antimitochondrial autoantibodies (AMA) and additionally 50% of them have antinuclear antibodies (ANA). A 15-amino acid fragment (DRKASPPSGLWSPAY) from the C-terminal part of the nuclear envelope glycoprotein gp210 has been proposed as one of the antigenic targets for ANA. The aim of this work was to develop an immunoenzymatic assay for determination of gp210 autoantibodies using for its binding a synthetic pentadecapeptide derived from the gp210 amino acid sequence and to determine level of these autoantibodies in sera of patients with PBC and other autoimmune liver diseases from Poland. Polystyrene microtitration plates coated with the synthetic peptide were consecutively incubated with diluted sera, anti-human immunoglobulin G (IgG) antibodies conjugated with horseradish peroxidase, and with tetramethylobenzidine. Optical density (OD) was read at 450 nm. The mean values of the intra- and interassay of variation coefficients of the test were 4.1 and 10.2%, respectively. Anti-gp210 was detected in 44% of PBC patients and in 6% of patients with PSC. The results were negative for healthy blood donors and other controls. The specificity of the test was 99%, so the anti-gp-210 autoantibodies estimated on DRKASPPSGLWSPAY can be a reliable marker of PBC.

Diagnostic relevance and clinical significance of the new enhanced performance M2 (MIT3) ELISA for the detection of IgA and IgG antimitochondrial antibodies in primary biliary cirrhosis

BACKGROUND/AIMS

Antimitochondrial antibodies (AMAs) are the serological hallmark of primary biliary cirrhosis (PBC). We evaluated the sensitivity and specificity of a new M2 enhanced performance enzyme-linked immunosorbent assay (ELISA) (MIT3) for the detection of IgG- and IgA-specific isotypes of AMA in PBC patients including a number of PBC patients negative for AMA by indirect immunofluorescence (IIF) as well as in patients with diverse, non-PBC disorders. We also investigated the clinical significance of IgG and IgA AMA in PBC.

METHODS

One hundred and three Greek PBC patients including 27 with AMA IIF-negative at the time of the investigation, 29 with autoimmune hepatitis-1 (AIH-1), 12 with primary sclerosing cholangitis (PSC), 26 with hepatitis C virus (HCV), 15 with hepatitis B virus (HBV), and 29 healthy were investigated for AMA (IgG and IgA) using the MIT3-based ELISAs (INOVA Diagnostics, San Diego, CA). The samples were also tested by conventional anti-M2 ELISA (INOVA Diagnostics, Inc.).

RESULTS

The IgG MIT3-based ELISA significantly increased AMA detection in the cohort of PBC patients, over 26% of whom were AMA IIF-negative, from 63.1% by the conventional anti-M2, and 73.7% by IIF to 79.6% by MIT3-based ELISA (p<0.001). IgA AMAs were detected in 47.6% patients. Overall, IgG/IgA AMAs were detected in 84/103 (81.6%). IgG MIT3-based ELISA detected 12/27 IIF AMA-negative samples (44.4%), while IgG/IgA MIT3-based ELISAs detected 13/27 IIF AMA-negative patients (48.1%). The specificities of MIT3-based ELISAs (IgG and IgA) were 82.8% and 89.7%, respectively, in AIH-1, 100% and 93.3%, respectively, in HBV, 100% in PSC, and 96% and 93.3%, respectively, in HCV. Patients positive for IgG AMA had significantly more severe disease as shown by worse histology and elevated biochemical markers; IgG and IgA AMA titers were associated positively with the Mayo risk score but none of the isotypes were able to predict disease outcome.

CONCLUSIONS

The new IgG and IgA MIT3-based ELISAs seem to have higher specificity and sensitivity for AMA detection than IIF and the conventional anti-M2. Interestingly, these assays were able to unmask AMA presence in almost half of the AMA-negative samples by IIF. These findings may suggest the use of MIT3-based ELISAs as first-line investigation for AMA detection, particularly, when the laboratories are unfamiliar with the use and interpretation of the IIF patterns of AMA. The presence of IgG AMA seems to characterize PBC patients with more severe disease, but both IgG and IgA isotypes of AMAs were not predictive markers of disease outcome.

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.

Applicability of the IAIHG scoring system to the diagnosis of antimitochondrial/anti-M2 seropositive variant form of autoimmune hepatitis

BACKGROUND AND AIMS

According to the International Autoimmune Hepatitis Group (IAIHG) criteria, circulating antimitochondrial antibodies (AMA) do not support the diagnosis of autoimmune hepatitis (AIH). The aims of this study were to characterize a subset of patients with AIH who have AMA and antiM2 seropositivity, and to assess the applicability of the revised scoring system of the IAIHG in the diagnosis of this variant form of AIH.

METHODS

Eighteen patients with AMA-AIH were enrolled and compared with 206 classical AIH and 85 primary biliary cirrhosis (PBC) controls. Human leukocyte antigen (HLA) class II alleles were determined by polymerase chain reaction (PCR) amplification with sequence-specific primers, and biopsies were blindly reevaluated.

RESULTS

The patients with AMA-AIH were, on average, older than patients with classical AIH and had an hepatocellular pattern of elevated liver enzymes, hypergammaglobulinemia and lower levels of cholesterol, when compared with PBC controls. There were no histological signs of PBC or overlapping forms in any AMA-AIH biopsies. The majority of patients with AMA-AIH carried HLA antigens associated with classical AIH (DRB1*03, n = 5; DRB1*04, n = 7, and DRB1*13, n = 6). Pretreatment scores classified all AMA-AIH patients with probable (n = 17) or improbable (n = 1) AIH. After treatment, only 28% of AMA-AIH patients reached scores for definite diagnosis, compared with 90.1% of AIH-1 and 96.4 AIH-2. In the AMA-AIH group, only patients who relapsed after immunosuppressive drug withdrawal could be classified with definite AIH.

CONCLUSIONS

AMA-AIH shares common features with classical AIH. The diagnosis of AMA-AIH may be swayed by the IAIHG criteria, rendering questionable the applicability of the revised scoring system to this variant form of AIH.

The presence of anti-mitochondrial antibodies in Chinese patients with liver involvement in systemic lupus erythematosus

Sixty-six hospitalized patients with systemic lupus erythematosus (SLE) were enrolled into this study. The test for anti-mitochondrial antibodies (AMAs) was performed and biochemical parameters were determined. AMAs were detected in 15 of the 66 patients with SLE. Meanwhile, we compared enzymatic levels in AMA-positive and -negative patients and found that serum aminotransferase levels were significantly higher in AMA-positive patients than in AMA-negative individuals. Furthermore, we found a positive correlation between serum AMA titration and serum aminotransferase levels. This study suggests that AMAs might contribute to the elevation of aminotransferases. Although much remains to be learned about the pathogenesis of autoimmune liver disease associated with AMAs, this report might provide greater insight into the metabolic mechanisms of AMAs in AMA-positive patients.

Increased serum aminotransferases associated with anti-mitochondrial antibodies in systemic lupus erythematosus patients with autoimmune liver disease

BACKGROUND

Serum aminotransferase activities are increased in many liver diseases, but the causes for the elevation might be difficult to determine. Whether the elevation of aminotransferases correlates with anti-mitochondrial antibodies (AMA) in systemic lupus erythematosus (SLE) patients with autoimmune liver disease deserves further consideration.

METHODS

A meticulous review was done in a large SLE cohort searching for laboratory features of the presence of AMA. Forty-eight hospitalized SLE patients with AMA and 60 randomly selected SLE patients without AMA as a matched case control were enrolled into the retrospective study. Laboratory data were collected, analyzed and compared in SLE patients with and without AMA.

RESULTS

Serum activities of aminotransferases were significantly increased in the 48 SLE patients with AMA compared with the 60 subjects without AMA. Meanwhile, we found a positive correlation between serum AMA titers and serum aminotransferase activities.

CONCLUSION

Although much remains to be learned about the pathogenesis of autoimmune liver disease associated with AMA, it is possible to suggest that AMA might contribute to the elevation of aminotransferases in SLE patients with the progressive disease.

Efficient isolation of cDNA clones encoding rheumatoid arthritis autoantigens by lambda phage surface display

Bacteriophage lambda surface display was used to isolate cDNA clones encoding autoantigens recognized by synovial fluid (SF) or sera from patients with rheumatoid arthritis (RA). We constructed cDNA libraries from human synovial sarcoma cells and synovial tissue, using the surface display vector lambdafoo. The cDNA libraries were screened by affinity selection using 40 SF and 44 sera as probes separately immobilized in microtiter wells. Phage clones isolated encode 13 different autoantigens; an unknown protein, two proteins previously unanalyzed as autoimmune antigens, three proteins previously unknown to be recognized by RA sera, and seven known RA antigens. When analyzed their sensitivity and specificity for RA by phage enzyme-linked immunosorbent assay, frequencies of sera that recognize the newly-isolated autoantigens ranged from 20.5 to 6.8% of a panel of RA sera, and 13.6-0% of other autoimmune disease sera. These results indicate that the lambda phage surface display may be powerful for the isolation of cDNA clones encoding autoantigens recognized by SF or sera from patients with not only RA but also other autoimmune diseases.

Peptidylarginine deiminase, the arginine to citrulline converting enzyme, is frequently recognized by sera of patients with rheumatoid arthritis, systemic lupus erythematosus and primary Sjögren syndrome

OBJECTIVE

Antibodies to citrulline-containing epitopes of filaggrin are highly specific for rheumatoid arthritis (RA). We studied whether the enzyme peptidylarginine deiminase (PAD), responsible for the post-translational modification of peptide-bound arginine residues to citrulline, constitutes an antigen for patients with RA.

METHODS

IgG antibodies to PAD were measured by enzyme-linked immunosorbent assay (ELISA) in sera from patients with RA, systemic lupus erythematosus (SLE), primary Sjögren syndrome (pSS), multiple sclerosis (MS) and healthy controls.

RESULTS

Compared to healthy controls, raised levels of IgG antibodies to PAD were found in 50 of 57 recent-onset RA patients (88%) and in 40 (70%) of the same 57 patients 3 years later (p<0.0001 for both comparisons). Eleven of 51 (22%) patients with RA of long duration, 19/43 (44%) patients with SLE and 16/19 (84%) patients with pSS, but none of 20 patients with MS, had elevated anti-PAD levels.

CONCLUSION

The arginine-citrulline converting enzyme PAD was recognized as a new antigen against which patients with inflammatory rheumatic diseases frequently show IgG class antibodies.

Characterization of M2 antibodies in asymptomatic Chinese population

AIM: To investigate the presence of M2 antibodies specific for primary biliary cirrhosis (PBC) in asymptomatic Chinese and identify patients with early PBC.

METHODS: Enzyme-linked immunosorbent assay (ELISA) tests for M2 antibodies to recombinant protein were performed in 5011 subjects (age range, 26-85 years; mean age: 45.81 ± 15.02 years) who took an annual physical examination. M2-positive subjects were further analyzed for immunoglobulin (Ig) classes and subclasses of M2 antibodies. Clinical, biochemical and immunological data were obtained for M2-positive subjects. In addition, ultrasonography (US) or endoscopic retrograde cholangio-pancreatography (ERCP) was performed to exclude any disorders other than PBC.

RESULTS: M2 antibodies were detected in 8 (0.16%) of the 5011 subjects studied. Of the 8 subjects, 7 were female and 1 was male (age range: 40-74 years). An unexplained increase of serum alkaline phosphatase (ALP) and gamma glutamyl transpeptidase (γ-GT) values, often to striking levels, was detected in 4 M2-positive subjects, 3 of them accorded with the diagnostic criteria recommended by the American Association for the Study of Liver Diseases, even though they had no symptoms of PBC (such as fatigue, pruritus or jaundice). Liver biopsy was performed in two M2-positive subjects and the histology was compatible with PBC in both cases.

CONCLUSION: Our data, while not assessing the true prevalence of asymptomatic PBC in the general population, suggest that asymptomatic PBC is much more common in China than has been supposed.

Construction and expression of a humanized M2 autoantigen trimer and its application in the diagnosis of primary biliary cirrhosis

AIM: To construct and express a humanized M₂ autoantigen trimer designated as BPO and to apply it in the diagnosis of primary biliary cirrhosis (PBC).

METHODS: cDNA fragments encoding M₂-reactive epitopes of pyruvate dehydrogenase complex E₂ (PDC-E₂), branched chain 2-oxo-acid dehydrogenase complex E₂ (BCOADC-E₂) and 2-oxo-glutarate dehydrogenase complex E₂ (OGDC-E₂) were amplified with PCR using total RNA extracted from human peripheral mononuclear blood cells. The fragments were cloned into the plasmid vector pQE-30 and then transferred into E. coli M15 (pREP4) for expression, which was induced by isopropylthio-β-D-galactoside. The expressed recombinant BPO protein was demonstrated by SDS-PAGE, Western-blotting and Immunoabsorption test, its antigenic reactivity and specificity were identified with seven M_---positive sera confirmed at Euroimmun Research Center (Germany). Using the purified BPO, M2 antibodies in sera from patients with PBC and other liver related diseases were detected with ELISA.

RESULTS: The expressed BPO was observed with both antigenic reactivity and specificity of M₂ autoantigens. The determination of M₂ antibodies by BPO with ELISA was more sensitive than using the Euroimmun's kit with the coefficients of variation less than 10% in both interassay and intraassay. With the newly established method, M2 antibodies were found in 100% (20/20) of patients with PBC. Six cases of liver disease with unknown etiology and 1 patient with drug induced liver injury had detectable levels of serum M₂ antibodies. There were also 2 patients with autoimmune cholangitis and 1 with autoimmune hepatitis showing M₂-antibody positive.

CONCLUSION: Compared with the routine immunofluorescence assay and commercially available assay kit using porcine heart mitochondrial protein as the antigen, the detection system established in the present study shows higher sensitivity and specificity and may be used as a powerful tool for the diagnosis of PBC.

Correlation between histopathological findings of the liver and IgA class antibodies to 2-oxo-acid dehydrogenase complex in primary biliary cirrhosis

Although anti-mitochondrial antibody (AMA) is the characteristic serological feature of primary biliary cirrhosis (PBC), its pathogenetic role remains unclear. We tested sera from 72 Japanese patients with histologically confirmed PBC for AMA by indirect immunofluorescence, anti-pyruvate dehydrogenase complex (PDC) by enzyme inhibition assay, immunoglobulin (Ig) G class anti-PDC by ELISA, and IgG, IgM, and IgA class anti-2-oxo-acid dehydrogenase complex (2-OADC) by immunoblotting. Of the 72 sera, 60 (83%), 50 (69%), 42 (58%), and 71 (99%) were positive for AMA by immunofluorescence, enzyme inhibition assay, ELISA, and immunoblotting, respectively. There was no significant correlation between histological stages and AMA by immunofluorescence, PDC inhibitory antibodies by enzyme inhibition assay, IgG class anti-PDC antibodies by ELISA, or IgG and IgM class anti-2-OADC by immunoblotting. IgA class anti-2-OADC by immunoblotting was more frequent in stages 2-4 than in stage 1 (P = 0.0083). Of the IgA class anti-2-OADC, anti-PDC-E2 (74 kDa) and anti-E3BP (52 kDa) were more frequent in stages 2-4 than in stage 1 (P = 0.0253 and 0.0042, respectively). Further examination of histopathological findings in 53 of 72 liver biopsy specimens showed that IgA class anti-PDC-E2 and IgA class anti-E3BP were associated with bile duct loss, and IgA class anti-PDC-E2 was also associated with interface hepatitis and atypical ductular proliferation. IgA is known to be secreted into the bile through biliary epithelial cells, implying that IgA class anti-PDC-E2 and E3BP may have a specific pathogenetic role during their transport into the bile by binding to their target antigen(s) in biliary epithelial cells, and this may be followed by dysfunction and finally destruction of biliary epithelial cells. Our present results suggest that these autoantibodies against 2-OADC detected by immunoblotting may be associated with the pathogenesis and pathologic progression of PBC.

The immunology of primary biliary cirrhosis: the end of the beginning?

The chronic liver disease primary biliary cirrhosis (PBC) is characterised by autoreactive B-cell and T-cell responses directed against mitochondrial antigens. In recent years these responses have been extensively characterised and the principal PBC associated autoantigen identified as pyruvate dehydrogenase complex (PDC). The identification of anti-PDC responses (present in over 95% of PDC patients) has given rise to important questions pertinent to our understanding of the pathogenesis of PBC. What specific role to anti-PDC responses play in target cell damage? How and why does immune tolerance break down to as highly conserved and ubiquitously expressed self-antigen as PDC? Why does breakdown in tolerance to an antigen present in all nucleated cells result in damage restricted to the intra-hepatic bile ducts? In attempting to answer these key questions we have, in this review, proposed a unifying hypothesis for the pathogenesis of PBC.

Automated enzymatic mitochondrial antibody assay for the diagnosis of primary biliary cirrhosis: applications of a routine diagnostic tool for the detection of antimitochondrial antibodies

BACKGROUND AND AIMS

An automated enzymatic mitochondrial antibody assay (EMA) kit for the diagnosis of primary biliary cirrhosis (PBC) has become commercially available recently. The aim of this study was to assess the clinical utility of the enzyme inhibition assay using this EMA kit for the diagnosis of PBC.

METHODS

We tested the immunoreactivity of sera from 54 histologically confirmed Japanese PBC patients to the 2-oxo-acid dehydrogenase complex (2-OADC) enzymes by enzyme inhibition assay using commercially available TRACE (EMA) assay kit, and compared the results with those of indirect immunofluorescence, commercial enzyme-linked immunosorbent assay (ELISA) using MESACUP Mitochondria M2 kit, and immunoblotting on bovine heart mitochondria.

RESULTS

Of the 54 sera, 43 (80%) were positive for antimitochondrial antibodies (AMA) by immunofluorescence, 39 (72%) for enzymatic inhibitory antibody to pyruvate dehydrogenase complex (PDC) by EMA, 33 (61%) for immunoglobulin G (IgG) class anti-PDC antibody by ELISA, and 53 (98%) for IgG, IgM, or IgA class antibodies against at least one of the 2-OADC enzymes by immunoblotting. Of these, 43 (80%) were positive for IgG, IgM, or IgA class antibodies against the E2 subunit of PDC (PDC-E2) by immunoblotting. Thirty-six of the 54 sera (67%) showed identical results in all of the four assays, and 40 (74%) were all negative or positive by EMA, ELISA, and immunoblotting in PDC-relevant reactivity. There was a significant correlation between the number of detected immunoglobulin classes of anti-PDC-E2 by immunoblotting and anti-PDC by EMA (P < 0.0001), and a significant inverse correlation between IgG class anti-PDC by ELISA and units of PDC activity by EMA (r = -0.87, P < 0.0001).

CONCLUSIONS

Although EMA had lower sensitivity compared with immunofluorescence and immunoblotting, this assay should be included among the routine diagnostic tools for the detection of AMA specific to PBC in clinical laboratories because of its high specificity, objective read-out, and rapid turnaround time.