Anti-pyruvate dehydrogenase autoantibodies in primary biliary cirrhosis

Tracing environmental markers of autoimmunity: introducing the infectome

We recently introduced the concept of the infectome as a means of studying all infectious factors which contribute to the development of autoimmune disease. It forms the infectious part of the exposome, which collates all environmental factors contributing to the development of disease and studies the sum total of burden which leads to the loss of adaptive mechanisms in the body. These studies complement genome-wide association studies, which establish the genetic predisposition to disease. The infectome is a component which spans the whole life and may begin at the earliest stages right up to the time when the first symptoms manifest, and may thus contribute to the understanding of the pathogenesis of autoimmunity at the prodromal/asymptomatic stages. We provide practical examples and research tools as to how we can investigate disease-specific infectomes, using laboratory approaches employed from projects studying the “immunome” and “microbiome”. It is envisioned that an understanding of the infectome and the environmental factors that affect it will allow for earlier patient-specific intervention by clinicians, through the possible treatment of infectious agents as well as other compounding factors, and hence slowing or preventing disease development.

Infectome: a platform to trace infectious triggers of autoimmunity

The "exposome" is a term recently used to describe all environmental factors, both exogenous and endogenous, which we are exposed to in a lifetime. It represents an important tool in the study of autoimmunity, complementing classical immunological research tools and cutting-edge genome wide association studies (GWAS). Recently, environmental wide association studies (EWAS) investigated the effect of environment in the development of diseases. Environmental triggers are largely subdivided into infectious and non-infectious agents. In this review, we introduce the concept of the "infectome", which is the part of the exposome referring to the collection of an individual's exposures to infectious agents. The infectome directly relates to geoepidemiological, serological and molecular evidence of the co-occurrence of several infectious agents associated with autoimmune diseases that may provide hints for the triggering factors responsible for the pathogenesis of autoimmunity. We discuss the implications that the investigation of the infectome may have for the understanding of microbial/host interactions in autoimmune diseases with long, pre-clinical phases. It may also contribute to the concept of the human body as a superorganism where the microbiome is part of the whole organism, as can be seen with mitochondria which existed as microbes prior to becoming organelles in eukaryotic cells of multicellular organisms over time. A similar argument can now be made in regard to normal intestinal flora, living in symbiosis within the host. We also provide practical examples as to how we can characterise and measure the totality of a disease-specific infectome, based on the experimental approaches employed from the "immunome" and "microbiome" projects.

The F1F0 ATP synthase and mitochondrial respiratory chain complexes are present on the plasma membrane of an osteosarcoma cell line: An immunocytochemical study

F(1)F(0) ATP synthase is ectopically expressed on the surface of several cell types, including endothelium and cancer cells. This study uses immunocytochemical detection methods via highly specific monoclonal antibodies to explore the possibility of plasma membrane localization of other mitochondrial proteins using an osteosarcoma cell line in which the location of the mitochondrial reticulum can be clearly traced by green fluorescent protein tagging of the organelle. We found that subunits of three of the four respiratory chain complexes were present on the surface of these cells. Additionally, we show for the first time that F(0) subunits d and OSCP of the ATP synthase are ectopically expressed. In all cases the OXPHOS proteins show a punctate distribution, consistent with data from proteome analysis of isolated lipid rafts that place the various mitochondrial proteins in plasma membrane microdomains. We also examined the cell surface for marker membrane proteins from several other intracellular organelles including ER, golgi and nuclear envelope. They were not found on the surface of the osteosarcoma cells. We conclude that mitochondrial membrane proteins are ectopically expressed, but not proteins from other cellular organelles. A specific mechanism by which the mitochondrion and plasma membrane fuse to deliver organellar proteins is suggested.

Autoantibodies in autoimmune liver disease

Autoantibodies indicate an immune reactive state, but in liver disease they lack pathogenicity and disease specificity. Antinuclear antibodies, smooth muscle antibodies, antibodies to liver/kidney microsome type 1, antimitochondrial antibodies, and perinuclear antineutrophil cytoplasmic antibodies constitute the standard serological repertoire that should be assessed in all liver diseases of undetermined cause. Antibodies to soluble liver antigen/liver pancreas, asialoglycoprotein receptor, actin, liver cytosol type 1, nuclear antigens specific to primary biliary cirrhosis, and pore complex antigens constitute an investigational repertoire that promises to have prognostic and diagnostic value. These autoantibodies may emerge as predictors of treatment response and outcome. Antibodies to histones, doubled-stranded DNA, chromatin, and lactoferrin constitute a supplemental repertoire, and they support the immune nature of the liver disease. Final diagnoses and treatment strategies do not depend solely on serological markers. Autoantibodies are floating variables, and their behavior does not correlate closely with disease activity. There are no minimum levels of significant seropositivity, especially in children. Over-interpretation is the major pitfall in the clinical application of the serological results. New autoantibodies will emerge as the search for target antigens and key pathogenic pathways continues.

Evaluation of the BioPlex 2200 ANA screen: analysis of 510 healthy subjects: incidence of natural/predictive autoantibodies

The BioPlex 2200 ANA Screen is a fully automated system that determines levels for 13 different autoimmune antibodies of established clinical significance. The objective of this study was to determine the specificity of the BioPlex 2200 ANA Screen assay and to analyze the antibody profile samples collected from healthy subjects against comparative ELISA and IIF screening methods. A total of 510 specimens were randomly selected from a cohort of apparently healthy blood bank donors. Samples were distributed to five age brackets. All samples were tested using Bio-Rad's ANA Screen kit. Specificity was compared to IIF and ELISA results. Most of the samples were found negative in all ANA screening systems (84.5% by IIF, 92.5% by BioPlex 2200 ANA Screen kit, and 94.5% by ELISA). The frequency of positive results was highest (15.5%) using IIF, in comparison to almost similar results (5.5% vs. 7.5%) achieved by ANA ELISA and BioPlex 2200 ANA Screen kits. The positive rate of autoantibodies was significantly reduced when analyzed by different combinations of ANA screen assays (from 2.35% using IIF + BioPlex ANA Screen tests to 0.98% by using all three tests). Using the BioPlex 2200 ANA Screen system, we were able to identify samples with high levels of individual antibodies: anti-dsDNA at 20-63 IU/mL, antichromatin at 4-8 AI, anti-SmRNP at 2-6 AI, and anti-RNPA at 2-4.5 AI. Importantly, from 7 IIF and ELISA positive sera, 5 of these were also BioPlex 2200 positive, suggesting that the BioPlex is seeing the samples that are of the greatest interest, using the established techniques. The specificity of the BioPlex 2200 ANA Screen analysis of 13 different analytes (dsDNA, centromere B, chromatin, Jo1, ribosomal P, RNP 68, RNP A, Scl-70, Sm, SmPNP, SS-A52, SS-A60, SS-B) is comparable (P < 0.252) to the ELISA ANA screening test. Like the ELISA, the BioPlex 2200 has a lower (P < 0.001) positive rate than IIF for the autoantibody screening.

Automated enzymatic mitochondrial antibody assay for the diagnosis of primary biliary cirrhosis

Primary biliary cirrhosis is a progressive autoimmune disease that affects middle aged women, resulting in liver cirrhosis. We describe here an automated enzymatic mitochondrial antibody assay adapted for performance on laboratory analysers for the serological diagnosis of primary biliary cirrhosis. This assay detects the characteristic autoantibody directed against the 74kDa E2 subunit of the pyruvate dehydrogenase complex. Analysis of receiver operator characteristic curve data indicated that the automated enzymatic mitochondrial assay procedure discriminated clinically identified patients with primary biliary cirrhosis from normal subjects with a sensitivity of 83% and a specificity of 100%. This method compared favourably against a commercial ELISA method which had a sensitivity of 73% and a specificity of 100%. The automated enzymatic mitochondrial antibody assay is a high throughput assay of use for the routine diagnosis of patients with primary biliary cirrhosis with autoantibodies to the E2 subunit of the pyruvate dehydrogenase complex. The method is of potential value for economical and rapid screening to detect asymptomatic primary biliary cirrhosis in the at-risk segment of the population, namely middle aged women.

Is there a serological difference between men and women with primary biliary cirrhosis?

OBJECTIVE

Primary biliary cirrhosis (PBC) is an autoimmune disease affecting small intrahepatic bile ducts of the liver, causing destruction of the epithelium that results in eventual fibrosis and scarring. We still lack a complete epidemiological description of this disease, although interesting geographic differences in prevalence have been described. One consistent feature has been the relative scarcity of men with PBC. In fact, published ratios of women to men range from 3:1 to as high as 22:1. Thus far, the only clinical difference reported between men and women with PBC is a putative higher risk of hepatocarcinoma in men. Previous serological studies have shown that about 95% of all patients possess antimitochondrial antibodies to members of the highly conserved 2-oxo-acid dehydrogenase family of proteins, namely 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). However, there has been no information as to whether there is a difference in serological response between men and women. Using the serological hallmark of antimitochondrial antibodies (AMAs) and taking advantage of the availability of recombinant mitochondrial autoantigens, investigations were performed to determine if there were any serological differences between men and women with PBC.

METHODS

Sera were collected from 88 patients with PBC, of whom 46 were men and 42 were women. Using a combination of immunoblotting and enzyme-linked immunoabsorbent assay (ELISA) against beef heart mitochondria (BHM), recombinant PDC-E2, BCOADC-E2, and OGDC-E2, we determined the relative autoantibody reactivities of our study population.

RESULTS

Both men and women with PBC produced high titer antimitochondrial antibodies. The frequency of reactivity was similar in both groups and included, in descending order, PDC-E2, E3BP (Protein X), BCOADC-E2, and finally OGDC-E2. More importantly, antigenic specificity was nearly identical regardless of gender.

CONCLUSIONS

AMAs are the serological hallmark of PBC in both men and women, and there is no significant difference in reactivity between the two groups of patients.

Argininosuccinate lyase: a new autoantigen in liver disease

Anti-liver cytosol 1 autoantibody (LC1) characterizes a severe form of autoimmune hepatitis (AIH), staining the cytoplasm of periportal hepatocytes and targeting an unidentified 60-kD liver cytosolic antigen. To identify its target, we used high-titre anti-LCI+ sera from two patients with AIH to screen 18 cytoplasm enzymes with periportal location by double immunodiffusion (DDI). Both sera gave a broad precipitin line against human liver cytosol, suggesting that they may recognize two distinct antigens, a possibility confirmed by the appearance of two precipitin lines when DDI conditions were optimized (0.8% agarose and 3% polyethylene glycol (PEG)). Experiments by DDI and Western blot (WB) identified a liver cytosolic autoantigen of 50 kD, different from LC1, giving a line of identity with argininosuccinate lyase (ASL). Reactivity to ASL was then investigated by DDI and WB in 57 patients with AIH, 17 with primary biliary cirrhosis (PBC), 15 with chronic hepatitis B virus (HBV) infection, 13 with alphal-antitrypsin deficiency, 17 with Wilson's disease, 18 with extrahepatic autoimmune disorders, and in 48 healthy controls. Anti-ASL was found in 16% of AIH and 23% of PBC patients by DDI and in 14% of AIH, 23% of PBC and 20% of HBV patients by WB. No argininosuccinate was present in the urine of four anti-ASL+ patients tested, excluding an inhibition of enzymatic activity by anti-ASL. The addition of anti-ASL+ serum to human fibroblast cultures induced a significant increase in ASL activity. ASL is a new autoantigen in liver disease and its clinical relevance warrants further investigation.

Primary biliary cirrhosis. Is (and how much of) the pathology preventible?

Primary biliary cirrhosis (PBC) is a chronic, progressive cholestatic liver disease, which is invariably fatal. Circumstantial and indirect evidence suggests that autoimmune mechanisms have a role in the pathogenesis of PBC. Antimitochondrial antibodies (AMA) are highly sensitive and specific markers that can predict the development of the disease in a healthy individual. Long-term administration of ursodeoxycholic acid (UDCA), a naturally occurring bile acid, safely slows the progression of PBC, delays the need for liver transplantation, and postpones death. An effort should be made to identify the patients with PBC in the asymptomatic stage by the presence of AMA and to conduct a clinical trial in order to assess the benefit of long-term administration of UDCA on the prevention of the overt disease in these individuals.

Antibodies to P450IID6, SLA, PDH-E2 and BCKD-E2 in Japanese patients with chronic hepatitis

Auto-antibodies specific to various antigens in chronic hepatitis (CH) have been detected but their specificities and implications were uncertain. The aims of the present study were to investigate the frequency and the significance of seropositivity of antibodies to P450IID6 or liver/kidney microsome 1 (LKM1), soluble liver antigen (SLA), pyruvate dehydrogenase (PDH) and branched-chain keto acid dehydrogenase (BCKD) in 188 Japanese patients with different forms of CH by western blot or enzyme immunoassay (EIA). Anti-LKM1 was also measured by indirect immunofluorescent test. Anti-P450IID6 was found in 6/188 (3.2%) CH patients including 5/104 (4.8%) with hepatitis C virus (C) infection and 1/12 (8.3%) CH-C patients with antibodies to nuclear and smooth muscle antigens and hypergammaglobulinaemia (> 2.5 g/dL). This patient was the only one diagnosed with autoimmune hepatitis (AIH). All CH patients with hepatitis B (B), hepatitis non-B non-C (NBNC) and AIH were seronegative for anti-LKM1. Antibodies to soluble liver antigen were found in two of 188 (1%) patients, one with AIH and one with CH-B. Anti-BCKD-E2 but not anti-PDH-E2 was found in four patients (2.5%), one with AIH, two with CH-C, and one with NBNC. There was no obvious difference in age, sex ratio and laboratory findings in patients with or without anti-SLA and anti-BCKD-E2. Antibodies to P450IID6, SLA, PDH-E2 and BCKD-E2 are uncommon in adult CH-C, CH-B, CH-NBNC and AIH patients in Japan. Some of these patients positive for auto-antibodies appear to have autoimmune features and might require a careful follow up. The heterogeneity of these antibodies in CH preclude further justification for subtyping of AIH by the presence of the distinct auto-antibodies.

Frequency and significance of antibodies to P450IID6 protein in Japanese patients with chronic hepatitis C

BACKGROUND/AIMS

The aims of the current study were to assess the frequency and the significance of antibodies to cytochrome P450IID6 protein (anti-P450IID6) in various diseases among Japanese patients.

METHODS

Sera from 541 patients were tested by indirect immunofluorescence, and the specificity of anti-P450IID6 was ascertained by either enzyme immunoassay (ELISA) or Western blot using recombinant antigen or rat liver microsomes.

RESULTS

Anti-P450IID6 was found in only 6 of 235 patients (2.6%) with chronic active hepatitis (CAH) positive for hepatitis C virus (HCV) antibody and quantitative HCV-RNA with genotypes II and IV. The predominant epitopes on immunoblots were 66 and 50KD, a 10KD band being the newly underfined microsomal antigen. Even in the patients negative for autoantibodies to nuclear antigens (ANA) by routine indirect immunofluorescence test, various ANA were detected by the newly developed recombinant ELISA. These patients were younger, with lower gamma-globulin and IgG levels than patients with autoimmune hepatitis. Three of five patients with anti-P450IID6 responded well to interferon therapy and one received prednisone when interferon was ineffective. Interestingly, only this patient was diagnosed as definite autoimmune hepatitis according to the criteria proposed by the International Autoimmune Hepatitis Group (IAHG). The other five patients who did not satisfy the IAHG criteria might be considered as CAH-C with autoimmune features. No autoimmune hepatitis patients positive for anti-P450IID6 were identified in the current study, indicating that the variant is very rare in Japan.

CONCLUSIONS

Anti-P450IID6 in CAH-C patients in Japan is not as rare as expected. Anti-P450IID6 among Japanese patients has uncertain significance and precludes further characterization of CAH-C with autoimmune features, which might require interferon therapy.

Autoantibodies in leprosy sera

Our objective was to assess the prevalence of autoantibodies in patients with leprosy. Forty-one cases of lepromatous leprosy were studied. For the detection of autoantibodies we used the Elisa technique using the following purified antigens in an Elisa assay: dsDNA, ssDNA, histone, mitochondria, RNA, RNP, SS-A, SS-B, Sm, Scl-70, Anca C, Anca P and the cardiolipin complex. As a "cut off" point we used values shown on previous studies to differentiate normal from elevated values. Antibodies to SS-B, mitochondria and cardiolipin were the most prevalent in our study. Antimitochondrial antibodies distinct from those seen in primary biliary cirrhosis and antiphospholipid antibodies with variable ligand activity to B2GIP are frequent in the sera of leprosy patients.

Kinetics of anti-M2 antibodies after liver transplantation for primary biliary cirrhosis

BACKGROUND/AIMS

Orthotopic liver transplantation is currently considered as the treatment of choice for primary biliary cirrhosis in the terminal stage and, as for other autoimmune liver disease, the risk of recurrence of the disease within the graft has been raised. There is, however, some discrepancy about the risk of recurrence based on pathological analysis. In addition, pathological recurrence of primary biliary cirrhosis within the graft is not always associated with a rise in the serological markers of the disease. In order to clarify this situation, we have monitored antimitochondrial antibodies before and after transplantation.

METHODS

Antimitochondrial antibodies were detected by indirect immunofluorescence (variation in antibody titers) and the antimitochondrial antibodies-2 by western blotting (variation in the number of peptides recognized in 16 primary biliary cirrhosis patients followed for at least 4 years after transplantation.

RESULTS

Antimitochondrial antibody titers had normalized 1 year after transplantation in seven patients, declined in seven others and remained unchanged in two. Over the 4 years of follow up, four patients demonstrated a subsequent increase in antimitochondrial antibody titers. Western blot analysis demonstrated the loss of one or more bands in seven patients during the first operative year after transplantation and in three other patients thereafter; in six patients the western blotting profile remained identical to that obtained before transplantation. The important changes generally occurred during the first year post-transplantation, without significant changes thereafter, except for three patients who demonstrated a secondary reappearance of the initially lost band. Disappearance of all bands was never observed. There was no concordance between the normalization of antimitochondrial antibody titers (indirect immunofluorescence) and the reduction in the number of peptides recognized (western blotting). Serum bilirubin and alkaline phosphatase levels had normalized by 1 year after transplantation, and remained normal thereafter. Routine liver biopsies performed on a yearly basis did not disclose any pattern suggestive of primary biliary cirrhosis recurrence.

CONCLUSIONS

Antimitochondrial antibody titers decreased in primary biliary cirrhosis patients after liver transplantation, although antimitochondrial antibodies-2 never disappeared as assessed by western blotting. In the present study these features were not associated with biochemical or histological (correction of histoclogical) evidence of primary biliary cirrhosis recurrence.

Multireactive pattern of serum autoantibodies in asymptomatic individuals with immunoglobulin A deficiency

Selective immunoglobulin A (IgA) deficiency (sIgAD) is associated with certain autoimmune states. Increased production of autoantibodies and eventual development of overt autoimmune disease are related in part to genetic and environmental factors as well as to the immune deficiency. We surveyed serum specimens from 60 healthy subjects with sIgAD for the presence of 21 different autoantibodies by enzyme-linked immunosorbent assays. The frequencies of 16 autoantibodies were higher in sIgAD patients than in normal healthy controls. Autoantibodies to Jo-1 (28%), cardiolipin (21%), phosphatidylserine (20%), Sm (15%), asialo-GM1 (21%), sulfatide (32%), sulfoglucuronyl paragloboside (11%), and collagen type I (10%) were detected at high frequencies in comparison to those of normal healthy controls. Many of the serum samples were multireactive (i.e., exhibited binding to more than two autoantigens). Forty percent (24 of 60) of sIgAD serum samples reacted against six or more autoantigens; 10% (6 of 60) of sIgAD serum samples were not reactive with any of the 21 autoantigens. Three percent (7 of 209) of consecutive serum samples submitted for autoimmune antibody analysis that were positive for autoantibodies were from patients with IgA deficiency. Our finding of an increased frequency of autoantibodies in sIgAD patients supports the notion of polyclonal stimulation by repeated environmental stimuli as an etiologic mechanism. Alternatively, the increased frequency may be caused by a dysregulation of the immune response in such individuals. The mere detection of autoantibodies cannot predict whether a subject with sIgAD will develop an autoimmune disease or determine which specific disease will emerge.

Antiphospholipid syndrome and the idiotypic network

To study whether monoclonal anticardiolipin antibodies (aCL), derived from patients with antiphospholipid syndrome (APS), have similar pathogenic potential, we have employed an experimental model of antiphospholipid syndrome. Monoclonal aCL were produced by the combined method of EBV transformation and somatic cell hybridization of lymphocytes, derived from patients with APS. The monoclonal aCL were used to immunize mice at the footpads and the mice were followed for serological and clinical manifestations of APS. The monoclonal antibody EY2C9, was found to bind weakly to cardiolipin and other phospholipids (i.e. phosphatidyl-serine, phosphatidyl-ethanolamine and phosphatidyl-inositol). The antibody TM1B9, although derived from a patient with SLE and with secondary APS, did not react with phospholipids. Immunization of naive BALB/c mice with EY2C9 was followed by production of sustained high titers of antiphospholipid antibodies associated with prolonged activated partial thromboplastin time (APTT) (46.8 +/- 5.0 s vs. 22.4 +/- 1.7 s, in the non-immunized mice). Mice immunized with TM1B9 had a more moderate titer of antiphospholipid antibodies and did not show prolonged APTT. The pregnant mice, that were immunized with EY2C9, had increased fetal resorption rate (the equivalent of fetal loss in the human) of 36.8 +/- 10% (vs. 2 +/- 4% in mice immunized with TM1B9). Our results confirm that monoclonal aCL, derived from a patient with APS, can have a pathogenic potential, dysregulating the idiotypic network and leading to the development of characteristic signs of APS.(ABSTRACT TRUNCATED AT 250 WORDS)

Identification and characterization of antimitochondrial autoantibodies in sera of patients with monoclonal gammopathies

Monoclonal gammopathies (MG) are defined by the accumulation of monoclonal immunoglobulins, a result of monoclonal B lymphocytes or plasma cell proliferative disorder. Only rarely do these antibodies cause an overt disease by binding to a specific autoantigen (e.g., factor VIII). In the present study, sera from 100 patients with MG were screened for the presence of antibodies against the mitochondrial pyruvate dehydrogenase complex (PDH) -- autoantibodies that are the hallmark primary biliary cirrhosis (PBC). Anti-PDH antibodies were found in 6 patients, all asymptomatic. Using ELISA and immunoblotting methods, it was found that the titre of the anti-PDH antibodies was relatively low (average OD +/- SD: 0.744 +/- 0.529; PBC patients: 1.225 +/- 0.291; P = 0.02). In each patient the autoantibodies were of both kappa and lambda chains, suggesting that they are of polyclonal origin and implying that in MG there is a significant production of polyclonal autoantibodies, in addition to monoclonal proliferation. Furthermore, in 5 of the 6 patients (83%) the anti-PDH antibodies did not recognize the E2 component of PDH (which is the major autoantigen in PBC) an did not inhibit the activity of PDH (which was inhibited by PBC autoantibodies). This is in concert with the fact that none of the patients developed liver disease and emphasizes the specificity of the anti-PDH autoantibodies associated with PBC.

Enzyme inhibitory autoantibodies to pyruvate dehydrogenase complex in primary biliary cirrhosis: applications of a semiautomated assay

Sera from patients with primary biliary cirrhosis inhibit the activity of the mitochondrial pyruvate dehydrogenase complex. We utilized this effect to develop a simple, miniaturized, semiautomated spectrophotometric assay as a diagnostic aid. The sera studied were from 71 patients with primary biliary cirrhosis and 62 other subjects. The assays included enzyme inhibition, immunofluorescence on HEp-2 cells, enzyme-linked immunosorbent assay using recombinant pyruvate dehydrogenase complex-E2 and immunoblotting on bovine heart mitochondria. With the 71 primary biliary cirrhosis sera, on which M2 antibody was detected by immunofluorescence in 64 (90%), antibodies against pyruvate dehydrogenase complex were detected in 53 (83%) by means of enzyme inhibition, in 57 (89%) by means of enzyme-linked immunosorbent assay and in 60 (94%) by means of immunoblotting. Of the 64 sera positive by immunofluorescence, 60 reacted with pyruvate dehydrogenase complex-E2 on immunoblotting, and the miniaturized enzyme inhibition assay was positive in 53 of these. The enzyme inhibition assay and enzyme-linked immunosorbent assay were calibrated to give a specificity of 100%. At this level, the sensitivities for detection of pyruvate dehydrogenase complex antibody were 83% and 87%, respectively. We found no significant changes in levels of reactivity with the enzyme inhibition assay or enzyme-linked immunosorbent assay according to disease stage. Treatment with cyclosporine was accompanied by a significant decrease in levels of antibody to pyruvate dehydrogenase complex-E2 that matched improved indexes of biochemical liver function.(ABSTRACT TRUNCATED AT 250 WORDS)

Isotypic distribution of anti-pyruvate dehydrogenase antibodies in patients with primary biliary cirrhosis and their family members

IgG subclasses of anti-pyruvate dehydrogenase (PDH) antibodies were determined in 72 patients with primary biliary cirrhosis. All isotypes were detected, but IgG3, IgG1, and IgG2 predominated independently or in association. An average of 33.3 +/- 19.1% of the anti-PDH IgG was IgG1 (mean optical density, 0.863 +/- 0.783, vs 0.053 +/- 0.038 in the normal controls), 25.0 +/- 17.8 IgG2 (0.652 +/- 0.656 vs 0.062 +/- 0.030), 39.5 +/- 23.4% IgG3 (1.140 +/- 0.917 vs 0.010 +/- 0.023), and 2.4 +/- 7.4% IgG4 (0.060 +/- 0.182 vs 0.012 +/- 0.007). Anti-PDH IgG were restricted to IgG1 in the family members of patients (0.180 +/- 0.403).

Antimitochondrial (pyruvate dehydrogenase) antibodies in leprosy

Sera from 69 patients with leprosy but without liver involvement were assayed for the presence of mitochondrial pyruvate dehydrogenase (PDH)-specific autoantibodies by enzyme-linked immunoabsorbent assay (ELISA), immunoblotting using PDH as an antigen and by enzymatic inhibition test. Twenty-seven of the leprosy serum samples (39.1%) were found to react with PDH by ELISA. However, unlike sera from primary biliary cirrhosis (PBC) patients, none of these were able to inhibit the PDH enzymatic activity. By immunoblotting, it was found that only 2 of the 27 positive sera recognized the 74-kD protein of the PDH complex, which is recognized by sera of most PBC patients. The antimitochondrial antibodies in lepra most probably recognize different epitopes than those in PBC. These findings may indicate that anti-PDH autoantibodies in patients with leprosy may arise by polyclonal B cell stimulation and may represent natural anti-PDH autoantibodies.

Antibodies to soluble liver antigen, P450IID6, and mitochondrial complexes in chronic hepatitis

BACKGROUND

Antibodies to soluble liver antigen, P450IID6, and the E2 subunits of mitochondrial dehydrogenase complexes occur in autoimmune liver diseases, but their specificities and implications are uncertain. The aims of the present study were to assess the importance of these autoantibodies in different types of chronic hepatitis.

METHODS

Sera from 62 patients with autoimmune hepatitis, 37 patients with cryptogenic hepatitis, and 19 patients with chronic hepatitis C were assessed under code by enzyme immunoassay.

RESULTS

Antibodies to soluble liver antigen were found in 7 patients with autoimmune hepatitis (11%) and 5 patients with cryptogenic disease (14%). Patients with antibodies to soluble liver antigen were indistinguishable from seronegative counterparts with autoimmune hepatitis. Seropositive patients with cryptogenic hepatitis had autoimmune features, and they responded to corticosteroid therapy. Five patients (8%) with autoimmune hepatitis were seropositive for antibodies to mitochondrial complexes. Three lacked antimitochondrial antibodies. None of the patients had antibodies to P450IID6, and patients with chronic hepatitis C were seronegative for all markers.

CONCLUSIONS

Antibodies to soluble liver antigen do not define a distinct subgroup of patients with autoimmune hepatitis. They may be found in some patients with corticosteroid-responsive cryptogenic hepatitis. Antibodies to E2 subunits and P450IID6 are uncommon in adults with chronic hepatitis.

Antimitochondrial (pyruvate dehydrogenase) autoantibodies in autoimmune rheumatic diseases

Anti-pyruvate dehydrogenase (PDH) antibodies were determined in 1451 sera of patients with primary biliary cirrhosis (PBC) and several autoimmune rheumatic conditions by ELISA and immunoblotting. They were detected in sera of 93% of the patients with PBC (179 of 192 patients) in 60 of 277 (22%) patients with Sjogren's syndrome (SjS), 34 of 437 (8%) patients with scleroderma, 33 of 191 patients with SLE (17%), and 5 of 55 (10%) patients with rheumatoid arthritis (RA) but in none of the patients with polymyositis or the antiphospholipid syndrome. The ELISA studies were confirmed by immunoblots showing binding of autoimmune rheumatic sera to the same epitope (74 kd) of mitochondria that the PBC sera reacted with. The identical binding characteristics were also confirmed by protein competition assays with purified PDH. In 4 of 53 patients with SjS who were positive for anti-PDH, high titers as in PBC were detected. The anti-PDH antibodies in Sjogren's patients were associated with deranged liver function tests and extraglandular features but did not correlate with any other non-organ-specific antibody. Follow-up studies confirmed the association of the emergence of anti-PDH antibodies with defects in liver function tests. The antibodies were more prevalent in SLE and RA when they were associated with Sjogren's syndrome (30 and 18.8%, respectively). Among patients with different forms of scleroderma, anti-PDH antibodies were noted in subjects with systemic sclerosis, morphea, and Raynaud's phenomenon.(ABSTRACT TRUNCATED AT 250 WORDS)