The human biliary epithelial cell plasma membrane antigen in primary biliary cirrhosis: pyruvate dehydrogenase X?

BACKGROUND & AIMS: Patients with primary biliary cirrhosis (PBC) have autoantibodies that react with components of mitochondrial multienzyme complexes. In addition to binding to mitochondria, patients' autoantibodies to the assumed major autoantigen pyruvate dehydrogenase complex (PDC) dihydrolipoamide acetyltransferase (E2) bind to the plasma membrane of biliary epithelial cells (BECs) specifically in PBC. The aim of this study was to characterize BEC plasma membrane antigens recognized by patients' autoantibodies in PBC. METHODS: Antigens prepared from intracellular and plasma membrane-enriched fractions of BECs purified from PBC and control liver were immunoblotted with anti-PDC. RESULTS: In the intracellular fraction, anti-PDC recognized BEC protein bands corresponding to the molecular weight value of E2 and X components of human heart PDC on Western blots. No difference was observed between PDC-E2 in BECs from PBC and controls. However, in PBC but not controls, a 50-kilodalton antigen was detected in the plasma membrane-enriched fraction. This antigen comigrated with component X of purified human heart PDC and was recognized by antibodies specific for PDC-X. CONCLUSIONS: The data suggest that PDC-X or a cross-reactive 50-kilodalton antigen is the BEC plasma membrane antigen recognized by patients' autoantibodies in PBC. Furthermore, this antigen, rather than PDC-E2, may be a major B-cell target antigen in PBC.     

Eosinophilia in primary biliary cirrhosis

OBJECTIVES: Recent studies have shown the occurrence of eosinophilia in patients with primary biliary cirrhosis (PBC). To examine whether eosinophilia is indeed a distinctive feature of PBC, we performed extensive leukocyte differential analysis using a highly sophisticated hematology instrument. We also investigated the relationship between eosinophil dynamics and clinical features of PBC including the effects of ursodeoxycholic acid (UDCA) treatment. METHODS: A flow cytometry-based blood cell analyzer (Technicon H6000) was used to examine peripheral blood eosinophil counts in 38 patients with PBC and 131 patients with various liver deseases. We also performed eosinophil quantitation in 19 PBC patients before and after administration of UDCA for 4 wk. RESULTS: Patients with PBC had significantly higher relative and absolute eosinophil counts when compared with other liver diseases (5.7 +/- 0.5% [p < 0.0001, mean +/- SEM] and 312 +/- 26 cells/microliter [p < 0.01], respectively). Twenty-one of 38 PBC patients (55%) exhibited relative eosinophilia. In patients with PBC, the eosinophil count was: 1) significantly higher in those with early histological stages (stage I-II, 6.5 +/- 0.5% vs stage III-IV, 4.4 +/- 0.7%,p < 0.05), 2) positively correlated with basophil count (p < 0.01), serum IgA levels (p < 0.05), and the degree of eosinophil infiltration in the portal tract (p < 0.01), and 3) markedly reduced by UDCA treatment (before: 5.9 +/- 0.7%, 307 +/- 37 cells/microliter; after: 2.8 +/- 0.03% [p < 0.001], 162 +/- 26 cells/microliter ?p < 0.001]). CONCLUSIONS: Eosinophilia is a common and distinctive feature of patients with PBC. UDCA ameliorates eosinophilia as well as liver function tests in PBC patients. Eosinophilia may be useful as one of the initial clues in the diagnosis of PBC, especially in its early stage.     

Antibodies to mycobacterial 65-kD heat shock protein cross-react with the main mitochondrial antigens in patients with primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is a chronic cholestatic liver disease associated with autoimmune disorders. The aetiology is unknown, although it has been suggested that the disease may be related to infectious agents. Previous studies revealed that sera from patients with PBC react against Mycobacterium gordonae. This specific reactivity, characterized by a recognition of two membrane polypeptides of 70-65 and 55 kD, cross-react with the two major mitochondrial autoantigens of PBC. As the most immunogenic components of mycobacteria are the heat shock proteins (hsp), which have been associated with autoimmunity, this study has been undertaken to characterize whether the reacting polypeptides in PBC are hsp from M. gordonae. Cultures of M. gordonae were incubated at 37 degrees C and 46 degrees C before sonication, protein extraction and separation by SDS-PAGE. Exposure of M. gordonae to heat shock treatment resulted in membrane protein overexpression, similar to the 70-65-kD polypeptide recognized by the sera from patients with PBC. Immunoprecipitation assays with a monoclonal antibody directed against the Hsp65 kD of mycobacteria and with sera from patients with PBC revealed similar reacting profiles characterized by the precipitation of the overexpressed 65-kD polypeptide from M. gordonae. Competitive immunoblotting showed that binding of the monoclonal antibody to the Hsp65 kD protein was prevented by preincubation with sera from patients with PBC, but not with sera from healthy subjects. Furthermore, monoclonal antibody to the Hsp65 kD protein recognized the main mitochondrial autoantigens of PBC (PDH-E2 and BCKDH-E2). These data indicate the existence of cross-reacting epitopes contained on M. gordonae Hsp65 kD and the main mitochondrial antigens in patients with PBC.     

Hepatocellular carcinoma in asymptomatic primary biliary cirrhosis

Hepatocellular carcinoma is an uncommon complication of primary biliary cirrhosis. Hepatocellular carcinoma occurs generally in the end stage of the disease. We report a case of asymptomatic primary biliary cirrhosis complicated by a hepatocellular carcinoma in a 66 year-old man.     

The geoepidemiology of primary biliary cirrhosis

Thirty-three species of fleas are recorded from the state of Tennessee. New state records are reported for two species, the pulicid fleas Euhoplopsyllus glacialis affinis and Pulex simulans. Two species of fleas with catholic feeding habits appear to be especially widespread and abundant in Tennessee. These are the pulicid Ctenocephalides felis which parasitizes cats, dogs, humans, opossums, and other medium to large sized mammals, and the hystrichopsyllid Ctenophthalmus pseudagyrtes which is associated with several species of small mammals, particularly shrews, moles, voles, and native mice. For a southeastern state, Tennessee has a relatively rich flea fauna. The figure of 33 flea species recorded here for Tennessee is higher than documented figures for other southeastern states (17 species for Alabama, 19 for Florida, 20 for Georgia, 12 for Mississippi, 18 for North Carolina, 19 for South Carolina). This is largely because several species with boreal origins inhabit the higher elevations characteristic of the Appalachian Mountains in the eastern part of the state. Although plague is not enzootic as far east as Tennessee, and murine typhus is rare of absent, suitable flea vectors inhabit the state and one abundant flea species, C. felis, is a pest because it feeds on companion animals and humans.     

Enhanced apoptosis relates to bile duct loss in primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is characterized by an immune-mediated destruction of intrahepatic small bile ducts. Apoptosis, a unique pattern of cell death, has been suggested to be responsible for the biliary destruction in PBC. To address this issue, we attempted to detect the apoptosis of biliary epithelial cells by in situ nick-end labeling and by the expression of apoptosis-related proteins using immunohistochemistry in patients with various hepatobiliary diseases, including PBC. The data was noteworthy for several reasons. First, apoptosis was occasionally detected on biliary cells in all liver specimens; however, the positive rate was high in PBC and relatively low in other livers. Strong expression of CD95 was frequently observed in the epithelial cells of the injured bile ducts of PBC, which accompanied high intensity CD95 ligand-expressing mononuclear cells. Perforin and granzyme B immunoreactivities were occasionally found on the bile ducts in control liver diseases as well as PBC, but granzyme B-positive biliary cells were prominent in PBC. In contrast, Lewis Y expression, as detected using BM-1 antibody, was consistently present in the injured bile ducts of PBC. These data suggest that apoptosis, via the perforin/granzyme B pathway, may be associated with the degrading fraction of cell cycle regulation in the small-sized biliary tree under physiological and pathological liver conditions. Moreover, enhanced apoptosis, mediated by CD95/CD95 ligand interaction, may contribute to the bile duct injury and loss observed in PBC.     

T cell responses to natural human proteins in primary biliary cirrhosis

The study of T cell responses to autoantigens in human autoimmunity has been hampered by difficulties, firstly in identifying significant autoantigens, and secondly in the purification of authentic human proteins in sufficient quantities to allow characterization of antigen-specific T cell responses. In this study we have purified a human autoantigen, pyruvate dehydrogenase, retaining its enzymatic activity, and characterized autoreactive T cell responses to it in a human autoimmune disease, primary biliary cirrhosis. T cell responses to a mixture of the E2 and protein X subunits of human pyruvate dehydrogenase complex are seen in most affected patients, but in only a small minority of normal and chronic liver disease controls. By contrast, responses to whole pyruvate dehydrogenase complex occur with equal frequency in both groups. This suggests that responses to the E2 component/protein X of pyruvate dehydrogenase complex play a role in the pathogenesis of primary biliary cirrhosis. The availability of significant quantities of the human autoantigen in primary biliary cirrhosis makes this condition an interesting model in which to study true autoreactive human T cell responses.     

Relationship between biliary and serum bile acids and response to ursodeoxycholic acid in patients with primary biliary cirrhosis

OBJECTIVE: Ursodeoxycholic acid (UDCA) improves liver biochemistries and enriches the bile with UDCA in patients with primary biliary cirrhosis. The aim of this study was to determine whether the degree of enrichment of bile correlated with that of serum and whether either of these measures correlated with improvement in measures of liver disease. METHODS: In a randomized study, biliary and serum bile acid analyses were performed at entry and after 2 yr of UDCA or placebo. RESULTS: The percentage of ursodeoxycholic acid in bile increased by 42% in the UDCA group (n = 61) compared with 8% in the placebo group (n = 57) (p < 0.0001). Measurement of serum bile acids in 32 patients (18 ursodeoxycholic acid, 14 placebo) indicated that at 2 yr, ursodeoxycholic acid comprised 65% of serum bile acids in the treated group and 7% in the placebo group. Agreement between bile and serum was fair (r = 0.75, p < or = 0.00002) because in some patients, plasma but not biliary bile acids were enriched with UDCA. Changes in biliary ursodeoxycholic acid correlated significantly but weakly with the changes in serum alkaline phosphatase, AST, bilirubin, and in Mayo risk score. Correlations between changes in serum bile acid composition and biochemical measures of disease activity were even weaker. CONCLUSION: The measurement of biliary bile acids is superior to that of serum bile acids for assessing the compliance and changes in the circulating bile acids in patients receiving ursodeoxycholic acid for the treatment of primary biliary cirrhosis. Furthermore, measures to further increase the proportion of ursodeoxycholic acid in circulating bile acids should be explored.     

Natural history of early primary biliary cirrhosis

BACKGROUND: In 1986, we reported a group of 29 patients who were positive in serum for antimitochondrial antibody (AMA), the disease-specific marker for primary biliary cirrhosis (PBC), but who had normal liver function test results and no symptoms of liver disease. However, liver histology was diagnostic or compatible with PBC in 24 patients and normal in only two. The aims of this 10-year follow-up study were to establish whether patients with AMA have very early PBC, to assess the outlook for such patients, and to follow the progression of the disease. METHODS: All patients were assessed every year at our PBC clinic: records were reviewed, cause of death verified when applicable, and current clinical and biochemical data collected, including repeat liver histology as indicated. Serum samples from the original study were located. Original and follow-up serum samples were tested by ELISA for E2 components of pyruvate dehydrogenase complex and 2-oxoglutarate dehydrogenase complex. FINDINGS: Five patients died during follow-up; no deaths were attributable to liver disease. Median follow-up of patients who survived was 17.8 years (range 11.0-23.9) from first-detected AMA to the last follow-up review. Overall, 22 (76%) developed symptoms of PBC and 24 (83%) had liver function tests persistently showing cholestasis. Repeat liver biopsy samples were obtained from ten patients; among these patients PBC progressed from Scheuer grade 1 to grade 2 in two and from grade 1 to grade 3 in two. No patient developed clinically apparent cirrhosis. ELISA of baseline serum samples from 27 patients was positive in 21, all of whom had original liver histology compatible with or diagnostic of PBC. Of the six patients who tested negative, only one had an original liver biopsy sample that was compatible with PBC. INTERPRETATION: This study confirms that before the advent of any clinical or biomedical indications, individuals positive for AMA do have PBC. This finding extends the natural history of PBC back in some cases for many years. What determines the eventual progression to biochemically and clinically apparent disease is not yet understood. During our study no patient developed clinically apparent portal hypertension or cirrhosis. Thus, although the finding of a solitary persistently raised AMA is confirmation of a diagnosis of PBC, patients with AMA but no other signs or symptoms of PBC seem to have slow progression of the disease.     

Mitochondrial antigen/antibody systems in primary biliary cirrhosis: revisited

Methods for the evaluation of the four antimitochondrial antibody subtypes in primary biliary cirrhosis - anti-M2, -M4, -M8, -M9 - are described. The importance of the application of different preparations for the demonstration of complement fixing antibodies and the detection of antibodies by ELISA or Western blotting is emphasized. Complement fixing antigens can be prepared by discontinuous isopynic sucrose density gradient centrifugation using mitochondrial subfractions derived with from beef heart (M2), rat liver (M4), or pig kidney (M8). Anti-M9 antibodies do not fix complement. For ELISA, the pyruvate dehydrogenase or the ATPase-associated antigen fraction (M2), the sulfite oxidase fraction (M4), and the chromatographically purified M8-fraction should be used. The same antigen fractions are suitable for Western blotting, but anti-M4 and anti-M8 by ELISA and Western blotting a purified fraction prepared from rat liver has to be applied. Correlating antimitochondrial antibody-subtypes with clinical condition and the natural course, there is convincing evidence that especially the presence of complement fixing antibodies against the subtypes M2, M4, and M8 is a reliable indicator for a more active course. Patients expressing only anti-M9 (without anti-M2) have biochemically all the typical features also found in classical anti-M2 positive primary biliary cirrhosis patients, but seem not to advance to late stages. Since these antimitochondrial antibody-subtypes are present even in very early stages stages without changing their pattern during the course, antimitochondrial antibody-profiles can also be taken as early prognostic parameters. The evaluation of the immunological activity by antimitochondrial antibody-subtype testing may further facilitate the decision whether therapy with ursodeoxycholic acid should be combined with steroids and/or immunosuppressive agents. The role of mitochondrial autoantigens in the induction of this chronic destructive bile duct process is also discussed. The concept is put forward that not bile ducts but naive(?) B-cells expose the different mitochondrial antigens, thereby stimulating autoreactive T-cells to provide a second signal for antibody production. The degree of breakage of tolerance to the different mitochondrial epitopes may be one crucial factor which determines the diversity of antimitochondrial antibody-subtypes in patients with primary biliary cirrhosis.     

Abnormal accumulation of endotoxin in biliary epithelial cells in primary biliary cirrhosis and primary sclerosing cholangitis

We measured levels of glucose and glycated hemoglobin in the blood of three of the world's smallest nectarivorous birds, the Anna's (Calypte anna), Costa's (Calypte costae), and ruby-throated hummingbirds (Archilochus colubris). Plasma glucose levels of hummingbirds that were fasted overnight (17 mM) were higher than those in any mammal and are among the highest ever measured in a fasting vertebrate. Glucose levels in hummingbirds just after feeding were extreme, rising as high as 42 mM. The surprisingly high blood glucose concentrations in hummingbirds were accompanied by glycated hemoglobin levels that are the highest ever measured in birds but are lower than those of non-diabetic humans. How hummingbirds tolerate blood glucose levels that cause serious neurological and microvascular pathologies in diabetic humans and animals remains unknown.     

Detection of retroviral antibodies in primary biliary cirrhosis and other idiopathic biliary disorders

BACKGROUND: Retroviruses have been implicated in the aetiology of various autoimmune diseases. We used immunoblots as a surrogate test to find out whether retroviruses play a part in the development of primary biliary cirrhosis. METHODS: We did western blot tests for HIV-1 and the human intracisternal A-type particle (HIAP), on serum samples from 77 patients with primary biliary cirrhosis, 126 patients with chronic liver disease, 48 patients with systemic lupus erythematosus, and 25 healthy volunteers. FINDINGS: HIV-1 p24 gag seroreactivity was found in 27 (35%) of 77 patients with primary biliary cirrhosis, 14 (29%) of 48 patients with systemic lupus erythematosus, 14 (50%) of 28 patients with chronic viral hepatitis, and nine (39%) of 23 patients with either primary sclerosing cholangitis or biliary atresia, compared with only one (4%) of 24 patients with alcohol-related liver disease or alpha1-antitrypsin-deficiency liver disease, and only one (4%) of 25 healthy volunteers (p=0.003). Western blot reactivity to more than two HIAP proteins was found in 37 (51%) of patients with primary biliary cirrhosis, in 28 (58%) of patients with systemic lupus erythematosus, in 15 (20%) of patients with chronic viral hepatitis, and in four (17%) of those with other biliary diseases. None of the 23 patients with either alcohol-related liver disease or alpha1-antitrypsin deficiency, and only one of the healthy controls showed the same reactivity to HIAP proteins (p<0.0001). Our results showed a strong association between HIAP seroreactivity and the detection of autoantibodies to double-stranded DNA. HIAP seroreactivity was also strongly associated with the detection of mitochondrial, nuclear, and extractable nuclear antigens. INTERPRETATION: The HIV-1 and HIAP antibody reactivity found in patients with primary biliary cirrhosis and other biliary disorders may be attributable either to an autoimmune response to antigenically related cellular proteins or to an immune response to uncharacterised viral proteins that share antigenic determinants with these retroviruses.