Biomedical subjects

M F Bassendine

Publications and source records attributed to M F Bassendine.

At least 19 recordsLinked to original sources

PubMed2006

Immunohistochemical assessment of hepatitis C virus antigen in cholestatic hepatitis after liver transplantation.

BACKGROUND: Patients with common variable immunodeficiency may exhibit rapidly progressive hepatitis when infected with hepatitis C virus (HCV), leading to cirrhosis and liver failure. Liver transplantation in these patients may result in a cholestatic form of HCV reinfection with exceptionally high virus loads. AIMS: To report an immunohistochemical investigation of the pretransplant and post-transplant liver of one such patient. METHODS/RESULTS: On immunohistochemical staining of frozen sections with anti-HCV core monoclonal antibody or fluorescein labelled human polyclonal anti-HCV IgG, no HCV antigens were demonstrated in the native cirrhotic liver removed at transplant, despite a viral load of 10(6.4) genomes/g. The transplanted liver, collected six weeks post-transplant, exhibited cholestatic recurrent hepatitis, had an HCV virus load of 10(10) genomes/g of liver, and revealed HCV antigen in the cytoplasm of most hepatocytes, with a pronounced periportal distribution. No virus antigen was demonstrable in other cell types. The core antigen was also detected in paraffin wax embedded, formaldehyde fixed tissue of this liver after high temperature antigen retrieval, but not in the native cirrhotic liver or a selection of HCV positive livers collected pretransplant from immunocompetent patients. Attempts to delineate the distribution of E1, NS3, and NS4 antigens were unsuccessful because monoclonal antibodies to these antigens produced "false positive" staining of foci of hepatocytes in the post-transplant livers of HCV seronegative patients with cholestasis. CONCLUSION: This case provided an opportunity to study the natural development of HCV during acute infection in the absence of an immune response, and may help to elucidate the pathogenesis of HCV recurrence in liver allografts.

Cholestasis, Intrahepatic↗

PubMed2005

Apolipoprotein epsilon3 allele is associated with persistent hepatitis C virus infection.

BACKGROUND: Host genetic factors may significantly influence the ability to clear hepatitis C virus (HCV) following infection. HCV is associated with very low density lipoproteins (VLDL) and low density lipoproteins (LDL) in the host's circulation. Apolipoprotein E (APOE) is found in VLDL and binds to potential receptors involved in HCV entry into cells, the LDL receptor, and the scavenger receptor protein SR-B1. The APOE gene is polymorphic with three alleles coding for three isoforms: Apo-epsilon2, Apo-epsilon3, and Apo-epsilon4. The aim of this study was to assess if these functional polymorphisms determine disease outcome in HCV infected individuals. METHODS: The APOE genotype was determined in 420 Northern European patients with evidence of exposure to HCV. Genotype and allele distribution were compared with those of 288 healthy controls and progression of liver disease and viral clearance were analysed according to APOE allele status. RESULTS: The APOE*E2 and APOE*E4 alleles were both associated with a reduced likelihood of chronic infection (odds ratio (OR) 0.39 (95% confidence interval (CI) 0.211-0.728), p = 0.003; and OR 0.6 (95% CI 0.38-0.96), p = 0.032) and there was a notable absence of the E2E2 genotype in the HCV antibody positive group compared with the control population (p = 0.0067). Overall the genotypes carrying the E2 allele (E2,E3 and E2,E4) were associated with the equivalent of a 3-5-fold reduction in the risk of chronic HCV infection (genotype relative risk 0.36 and 0.20, respectively). CONCLUSION: This study indicates that functional APOE gene polymorphisms may be a determinant of outcome in HCV infection. We hypothesise that the E2 allele may protect against viral persistence via defective binding of HCV lipoviral particles to the cellular receptors involved in entry of these infectious particles.

Alleles↗

PubMed2004

Tamoxifen: a novel treatment for primary biliary cirrhosis?

Primary biliary cirrhosis (PBC) is a chronic cholestatic liver disease, which predominantly affects women. It is characterised histologically by necroinflammation of small intrahepatic bile ducts and biochemically by elevated serum alkaline phosphatase, levels of which at diagnosis predict survival. Ursodeoxycholic acid (UDCA) is the only treatment shown to improve liver biochemistry and survival. We report two patients with PBC who show a fall in serum alkaline phosphates levels whilst receiving tamoxifen therapy. Tamoxifen may exert this effect, which warrants further study, either via cholangiocyte estrogen receptors, inhibiting cholangiocyte proliferation and inducing apoptosis or by activating pregnane X receptor, analogous to the mode of action of UDCA.

Aged↗

PubMed2004

Chemokine receptor 5 and primary biliary cirrhosis: a two-centre genetic association study.

BACKGROUND: Chemokines and their receptors are important mediators of leucocyte trafficking and are suggested to be critical for establishment of inflammatory autoimmune processes. CC chemokine receptor 5 (CCR5) is expressed preferentially by CD4+ T cells. We hypothesised that the CCR5delta(Delta)32 genotype, which impairs surface expression of CCR5 in heterozygotes and is linked to a functional polymorphism of CD45RA expressed on suppressor-inducer-like 'naive' CD4+ T cells, may modulate the inflammatory process in primary biliary cirrhosis (PBC). METHODS: CCR5Delta32 polymorphism was determined by PCR in 226 Caucasian PBC patients and 197 racially matched controls from two geographical areas, Newcastle, UK and Padua, Italy. (UK: 144 PBC, 105 controls, Italy: 82 PBC, 92 controls). RESULTS: When the two series were analysed separately, there were no significant differences in the genotype distribution comparing patients and controls (UK: wt/wt 72% vs 76%; wt/Delta32 28% vs 22%; Delta32/Delta32 0% vs 2%, P=0.24; Italy: wt/wt 72% vs 82%; wt/Delta32 27% vs 17%; Delta32/Delta32 0% vs 1%, P=0.14). However, when the data for the two series were pooled and reanalysed, we found an increase in the CCR5Delta32 mutation in PBC patients vs controls (28% vs 21%, OR=1.43, P=0.03), but there was no evidence that this Delta32 polymorphism is associated with less severe disease. CONCLUSIONS: Although this two-centre genetic association study is large compared with others performed in PBC, taken separately, each geographically based cohort of patients and controls is underpowered to detect a small effect of this functional polymorphism. This emphasises the need for far larger case-control collections to address which polymorphic markers or haplotypes might modify the pathogenesis and clinical course of PBC. We propose that multi-centre collaboration on an international scale in 'orphan' complex liver diseases such as (PBC) is supported by the International Association for the Study of the Liver and promoted via their journal with development of a brief format for web-based publication of studies.

Base Sequence↗

PubMed2002

Hepatitis C virus particles of different density in the blood of chronically infected immunocompetent and immunodeficient patients: Implications for virus clearance by antibody.

The purpose of this study was to analyse the influence of the humoral immune response on the generation and clearance of hepatitis C virus (HCV) RNA containing particles in the blood of chronically infected patients. Blood samples were fractionated by sequential flotation ultracentrifugation and HCV RNA was recovered in three fractions: low density of < 1.063 g/ml, intermediate density of 1.063-1.21 g/ml, and high density of > 1.21 g/ml. Serum low-density lipoproteins co-fractionated with the low-density particles, and high-density lipoproteins co-fractionated with the intermediate-density particles. Immunoglobulins were found exclusively in the high-density fractions. In patients with congenital immunodeficiencies, with no or low serum antibodies to the virus, mean HCV RNA titres were equal in each fraction, at approximately 10(5) IU/ml. In antibody-positive, immunocompetent patients, however, virus titres in the low-density fraction and those in the high-density fraction were reduced or absent in most patients, suggesting that virus particles in these fractions are subject to antibody-mediated clearance. Particles of intermediate density were approximately equal in titre in both patient groups, suggesting that these particles are neither generated by, nor cleared, as a result of the humoral immune response. Immunoprecipitation experiments indicated that particles of intermediate density were not complexed with either high-density lipoprotein or immunoglobulins. Elucidation of the mechanisms by which these particles are generated and maintained in the blood may provide valuable insight into the mechanism of virus persistence.

Adolescent↗

PubMed2002

Familial primary biliary cirrhosis and autoimmune cholangitis.

AIM: Autoimmune cholangitis has been proposed as a separate disease entity from primary biliary cirrhosis without serum antimitochondrial antibodies. The ultimate answer to the question of whether autoimmune cholangitis and primary biliary cirrhosis are distinct will require detailed comparison of aetiologic factors and pathogenic mechanisms. METHODS AND RESULTS: Two families are described each of which has one member with classical antimitochondrial antibody positive biopsy-proven primary biliary cirrhosis and a first degree relative with antimitochondrial antibody negative but antinuclear antibody positive autoimmune cholangitis (biopsy proven in one case). Study of such families should allow analysis of the contribution of shared genetic risk factors versus varying environmental triggering mechanisms to disease pathogenesis. CONCLUSIONS: We suggest a European registry of families, such as the two described, which are rare within one centre, to facilitate elucidation of pathogenetic factors.

Adult↗

PubMed2002

Hepatitis associated with Chinese herbs.

Traditional Chinese herbal medicines are widely available in Western society and are popular as a form of 'natural' alternative medicine. Their use is increasing, as they are perceived to be free of side effects, but they remain largely unregulated. We describe two patients who suffered severe hepatitis, one of whom died, after taking Chinese herbal remedies for minor complaints. We also review the English-language literature on hepatitis associated with Chinese herbs. Two products appear to be implicated frequently: Jin bu huan was taken by 11 patients, and Dictamnus dasycarpus was taken by six patients, including both fatal cases. It is difficult to provide conclusive evidence of what caused hepatitis, as these products are mixtures that may contain adulterants. These cases highlight not only the potential dangers of these products to consumers but also the need for greater control of their manufacture and use.

Adult↗

PubMed2001

Interferon plus amantadine versus interferon alone in the treatment of naïve patients with chronic hepatitis C: a UK multicentre study.

BACKGROUND/AIMS: The antiviral agent amantadine may have activity against the hepatitis C virus. To determine whether the combination of interferon-alpha plus amantadine was more effective than interferon monotherapy we conducted a multicentre clinical trial in untreated patients with chronic hepatitis C infection. METHODS: We performed a pilot study in two centres (36 patients) to determine the number needed for a statistically significant clinical trial and then conducted a multicentre, randomized controlled clinical trial involving 14 centres and 143 patients. RESULTS: There was no significant difference in sustained response rates in patients receiving interferon and amantadine compared to those receiving interferon alone. The on treatment response rate at 3 months was 65% on combination vs. 49% on interferon alone (P = 0.05) while the sustained response was 18 and 15%, respectively. CONCLUSIONS: Combination therapy with interferon plus amantadine does not lead to a significant increase in sustained response rates when compared to interferon monotherapy.

Adult↗

PubMed2001

Managing chronic hepatitis C acquired through intravenous drug use.

We retrospectively reviewed the provision and uptake of hospital services for 253 current and ex-intravenous drug users with hepatitis C virus (HCV). Overall, 237 attended at least one clinic (mean age 32 years, 70% male, 43% on maintenance methadone); 81% had evidence of active viral replication and 137 agreed to a liver biopsy to assess disease severity. Of these 137, 24% had mild chronic hepatitis with a low risk of progression to cirrhosis, but 9% had cirrhosis (mean age 40 years, mean time since initial intravenous drug use 15.8 years). Only 50 of the 100 patients in whom antiviral therapy was indicated, commenced treatment; 18 (36%) have had a sustained virological response. The natural history or response to treatment of chronic HCV in those who acquire it through intravenous drug use is not different to that previously reported for post-transfusion HCV. However, a substantial proportion default from follow-up or decline further intervention. As intravenous drug use is now the main risk factor for acquisition of HCV, these data have implications for future delivery of care aimed at limiting the morbidity of chronic HCV, and limiting the spread of hepatitis C virus infection amongst intravenous drug users.

Adolescent↗

PubMed2000

CTLA-4 gene polymorphism confers susceptibility to primary biliary cirrhosis.

BACKGROUND/AIM: Primary biliary cirrhosis (PBC) is an autoimmune cholestatic liver disease thought to develop through a complex interaction of genetic and environmental factors. It is characterised by T-cell-mediated non-suppurative destructive cholangitis. We have studied the polymorphic cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) gene, which encodes a molecule that is a vital negative regulator of T-cell activation, as a candidate susceptibility locus for PBC. This gene on chromosome 2q33 (designated IDDM12) is associated with susceptibility to both type 1 diabetes and autoimmune thyroid disease. METHODS: The CTLA-4 exon 1 polymorphism (A/G encoding for threonine or alanine, respectively) was genotyped via polymerase chain reaction in 200 Caucasoid PBC patients and 200 non-related geographically matched Caucasoid controls. RESULTS: There was significant overrepresentation of the G/A and G/G genotypes in PBC patients compared to controls (G/A 53% vs 40%; G/G 18.5% vs 10.5%, Odds Ratio (OR)=2.45 [95% CI 1.6-3.7], p=0.00006, chi2=19.4). Likewise, there was a significant difference in allele frequencies (G encoding alanine at codon 17, PBC 0.45 vs controls 0.305: OR=1.9 [1.4-2.5], p<0.0002). This association remained significant (p=0.00027) when patients with autoimmune thyroid disease were excluded from the analysis. CONCLUSIONS: The CTLA-4 exon 1 polymorphism is the first non-major histocompatibility complex gene to be identified as a susceptibility locus for PBC. Our data support the hypothesis that clinically distinct autoimmune disease may be controlled by a common set of susceptibility genes.

Abatacept↗

PubMed2000

Experimental autoimmune cholangitis: a mouse model of immune-mediated cholangiopathy.

BACKGROUND: Primary biliary cirrhosis (PBC) is characterised by intra-hepatic immune-mediated cholangiopathy (non-suppurative destructive cholangitis (NSDC)). Although auto-reactive immune responses against pyruvate dehydrogenase complex (PDC) have been characterised in PBC, the lack of an animal model of the disease has limited study of the mechanisms of disease induction and the development of novel approaches to therapy. AIMS: To develop and validate a mouse model of immune-mediated cholangiopathy relevant for future use in the study of the aetio-pathogenesis and therapy of PBC. METHODS: Female SJL/J, C57BL/6, NOD and BALB/c mice were sensitised with PDC, its purified E2/E3BP component, and a PDC-E2 derived peptide p163 (a dominant T-cell epitope in humans) in complete Freund's adjuvant (CFA). Morphological changes were assessed under light microscopy by a hepatic histopathologist blinded to the experimental details. Antibody responses to PDC were studied by ELISA and PDC inhibition assay. RESULTS: An initial series of experiments was performed to survey the susceptibility of female mice of a range of strains to the induction of NSDC by i.p. sensitisation with PDC, PDC-E2/E3BP or p163 in CFA. Although each animal showed a specific antibody response following sensitisation, it was found that NSDC development (assessed at 30 weeks post-sensitisation) was restricted to SJL/J mice following sensitisation with any of the mitochondrial antigen preparations. A subsequent series of experiments was performed to examine the specificity and aetiology of this disease. Significant bile duct lesions were only seen in SJL/J animals following sensitisation with CFA containing PDC, and were absent from CFA only and un-sensitised controls. Kinetic analysis revealed that this pathology developed slowly, but a high incidence of animals with severe lesions was observed after 30 weeks. CONCLUSIONS: We have described a model of experimental autoimmune cholangitis (EAC) with immunological (anti-PDC antibodies) and histological (immune-mediated cholangiopathy) features suggestive of PBC. This model may be useful in further defining the role of self-tolerance breakdown in the development of this condition.

Animals↗

PubMed2000

The effect of NAT2 genotype and gender on the metabolism of caffeine in nonsmoking subjects.

AIMS: To establish whether gender or N-acetyltransferase 2 (NAT2) genotype influence the urinary 17 U+17X/137X ratio after dosing with caffeine. METHODS: Ninety-two nonsmoking individuals underwent caffeine phenotyping. NAT2 genotype was determined by the polymerase chain reaction followed by a restriction digest (PCR-RFLP). RESULTS: The median ratio for urinary 17 U+17X/137X was 6.7 (range 1.45-18. 65). 55% of subjects were slow acetylators. Gender did not affect the metabolic ratio or NAT2 genotype. Mean 17 U+17X/137X ratio differed between fast (6.75) and slow (8.69) acetylators (95% CI for the difference, 0.32-3.56). CONCLUSIONS: The findings are further evidence that the 17 U+17X/137X urinary ratio is not a robust measure of CYP1A2 activity. A possible mechanism by which the ratio might be influenced by NAT2 genotype is suggested.

Adolescent↗

PubMed2000

Secretory autoantibodies in primary biliary cirrhosis (PBC).

It is unclear how breakdown in immune tolerance to the ubiquitous self-antigen pyruvate dehydrogenase complex (PDC), seen in the autoimmune liver disease PBC, gives rise to tissue damage with such a limited distribution (restricted to the liver and salivary and lachrymal glands). One property shared by these tissues is the ability to export secretory IgA by the process of transcytosis. The aim of this study was to address whether active transcytosis of anti-PDC IgA occurs across epithelial surfaces in PBC, a finding that might implicate mucosal specific immune mechanisms in the pathogenesis of this disease. Parotid saliva was collected from PBC patients (n = 44), normal controls (n = 28) and PBC patients post-liver transplantation (n = 11). IgA and secretory component-positive antibodies specific for human PDC were quantified by ELISA and immunoblotting. PBC patients (but not control subjects) had anti-PDC IgA in their saliva. The strong correlation seen between titres detected using anti-IgA and anti-secretory component antibodies suggests that this is predominantly secretory IgA reaching the saliva by the active process of epithelial transcytosis. Titres of anti-PDC IgA remain high in PBC patients saliva post-liver transplant. Findings from studies of IgA in viral infection models raise the possibility that anti-PDC IgA could, whilst undergoing transcytosis, bind to newly translated PDC components in the cytoplasm of the epithelial cells transporting them out of the cell and inducing metabolic damage. This model would, if correct, help to explain the mechanism and tropism of tissue damage in PBC and the aberrant pattern of expression of PDC on the apical surface of biliary and salivary epithelial cells reported in this disease.

Adult↗

PubMed2000

Presentation and mortality of primary biliary cirrhosis in older patients.

OBJECTIVES: many patients with primary biliary cirrhosis present for the first time aged over 65, but it is unclear whether the disease is different in older patients. We have examined presentation and mortality in relation to age at which primary biliary cirrhosis was first suspected clinically. DESIGN: we identified 1023 patients from our regional primary biliary cirrhosis database with definite or probable primary biliary cirrhosis (689 definite); 397 (39%) presented aged > or =65. Definite primary biliary cirrhosis was defined as a positive antimitochondrial antibody titre > or =1/40, abnormal liver enzymes and compatible/diagnostic histology; probable as the presence of two of these indications. RESULTS: there was no difference in presenting clinical features between the older and younger groups. Older patients were significantly less likely than younger to have had liver biopsy (50% vs 78%; P < 0.001). The 1023 patients had been followed for 8561 patient years. Follow-up was shorter (5.9+/-4 vs 9.8+/-5.5 years; P < 0.001) in the older group because of higher cumulative mortality (59% vs 33%; P < 0.001). Liver-related deaths were significantly commoner in the older group (18% vs 13%; P < 0.05). The mortality ratio for liver deaths (liver deaths per year of follow-up) was 2.4 times higher in the older group (0.031 vs 0.013). CONCLUSIONS: patients with primary biliary cirrhosis who are over and under 65 have similar features on presentation. The annual risk of liver death is 2.4 times higher in those presenting over 65, reaffirming the importance of age as an independent prognostic factor in an unselected primary biliary cirrhosis population.

Adult↗

PubMed2000

Interleukin 10 promoter region polymorphisms and susceptibility to advanced alcoholic liver disease.

BACKGROUND: The factors determining why less than 10% of heavy drinkers develop advanced alcoholic liver disease (ALD) remain elusive, although genetic factors may be important. Interleukin 10 (IL-10) is an important cytokine with anti-inflammatory, anti-immune, and antifibrotic functions. Several polymorphisms have been identified in the IL-10 promoter and recent evidence suggests that some of these may have functional effects on IL-10 secretion. AIMS: To test the hypothesis that IL-10 promoter region polymorphisms are associated with susceptibility to ALD. METHODS: The allele frequencies for the two single base pair substitutions at positions -627 (C-->A) and -1117 (A-->G) in the IL-10 promoter were determined in 287 heavy drinkers with biopsy proved advanced ALD, 107 heavy drinkers with no evidence of liver disease or steatosis only on biopsy, and 227 local healthy volunteers. RESULTS: At position -627, 50% of patients with advanced ALD had a least one A allele compared with 33% of controls (p<0.0001) and 34% of drinkers with no or mild disease (p=0.017). At position -1117, the slight excess of the A allele in drinkers with advanced disease was because of linkage disequilibrium between the A alleles at the two sites. CONCLUSIONS: Among heavy drinkers, possession of the A allele at position -627 in the IL-10 promoter is associated with an increased risk of advanced liver disease. This is consistent with recent functional data that the -627*A allele is associated with low IL-10 expression which will favour inflammatory, immune mediated, and profibrotic mechanisms of alcohol related liver injury.

Alleles↗

PubMed1999

Enhanced ultrasensitive detection of structurally diverse antigens using a single immuno-PCR assay protocol.

Our studies of DNA damage and repair in autoimmune disease, lymphomagenesis, and carcinogenesis, require identification of an immunoassay approach that is capable of ultrasensitive detection in a routine human tissue biopsy of several physicochemically diverse antigens, some of which will be present at very low level. Immuno-polymerase chain reaction (immuno-PCR) is a recently described method for ultrasensitive antigen detection that combines the amplification power of PCR with a method similar to a standard antibody capture, enzyme-linked immunosorbent assay (ELISA). As a test of the universality of immuno-PCR, and as an assessment of the suitability of this method for our studies, we used a single immuno-PCR protocol to assay purified forms of the following physicochemically diverse antigens: oligomeric pyruvate dehydrogenase complex (PDC; Mr 8.5 x 10(6)), the promutagenic DNA base adduct O(6)-methylguanosine (Mr 298) and its monomeric repair enzyme, O(6)-methylguanine-DNA methyltransferase (MGMT; Mr 22,000), and a peptide from the N-terminus of MGMT (Mr 2310). We found that all antigens could be ultrasensitively assayed using the single immuno-PCR protocol. Assay limits observed using antigen-specific (primary) antibodies at 1 microg/ml, were in the approximate range of 10(2)-10(9) molecules, with O(6)-methylguanosine being detected most sensitively. Sensitivity of the antigen assay appeared to positively correlate with primary antibody titres determined by ELISA. Furthermore, we observed a substantial increase in detection sensitivity for all antigens by the use of primary antibodies at the higher level of 10 microg/ml. The latter approach permitted antigen assay within the approximate range of 10(0)-10(7) molecules. The combination of higher titre primary antibodies and their use at higher input level, produced an increase of immuno-PCR assay sensitivity of up to four orders of magnitude greater than those previously reported through the use of this assay to measure other antigens. This represents up to a nine order of magnitude increase in immunoassay sensitivity compared to ELISA. Our findings provide compelling evidence that immuno-PCR is indeed a universal ultrasensitive antigen detection method. Using the indicated assay enhancements. immuno-PCR performed as detailed here can offer greatly increased sensitivity for antigen measurement compared to other methods. Thus, our findings suggest that parallel quantitation of several different antigens in very small samples of human tissue will be readily attainable using immuno-PCR.

Amino Acid Sequence↗

PubMed1999

Comparison of cytotoxic T-lymphocyte responses to hepatitis C virus core protein in uninfected and infected individuals.

Cytotoxic T lymphocytes have been implicated in the control of hepatitis C virus (HCV) infection. Recognition by cytotoxic T lymphocytes of epitopes within HCV core protein has been defined previously by in vitro stimulation with synthetic peptides. The aim of this study has been to examine cytotoxic T-lymphocyte responses generated against peptides produced naturally following intracellular processing of viral protein. Antigen-specific cytotoxic T-lymphocyte lines were generated from both HCV uninfected and infected individuals by culturing CD8+ T cells with autologous dendritic cells loaded intracytoplasmically with recombinant HCV core protein. Analysis of the epitopes recognized by core protein-specific cytotoxic T lymphocytes used synthetic peptides that were selected based on their predicted binding to HLA-A*0201 molecules. Core protein-specific cytotoxic T lymphocytes derived from HCV uninfected and infected individuals were able to lyse autologous target cells pulsed with each of 5 predicted epitopes. Generation of HCV-specific cytotoxic T lymphocytes using dendritic cells as antigen presenting cells provides a method of comparing the potential repertoire of cytotoxic T-lymphocyte responses to the responses that occur in chronically infected individuals. No evidence of a qualitatively different response by patient cytotoxic T lymphocytes was apparent which might explain persistence of the virus.

Cytotoxicity Tests, Immunologic↗

PubMed1999

Breakdown of tolerance to pyruvate dehydrogenase complex in experimental autoimmune cholangitis: a mouse model of primary biliary cirrhosis.

The autoimmune liver disease primary biliary cirrhosis (PBC) is characterized by autoreactive responses to a highly conserved self-antigen, pyruvate dehydrogenase complex (PDC). We recently reported the development of PBC-like lesions in SJL mice sensitized with PDC and have named this model disease experimental autoimmune cholangitis (EAC). In the present study, the breakdown of tolerance to PDC has been investigated in animals sensitized for EAC. Splenic mononuclear cells from SJL mice sensitized with bovine heart PDC (bPDC) in adjuvant showed T-cell proliferative and mixed Th1/Th2 cytokine secretory responses following in vitro stimulation with bPDC. Despite the likelihood of extensive sequence homology with mouse PDC (there is a greater than 95% sequence identity between rat and human PDC-E2 subunits), bPDC was highly immunogenic inducing significant T- and B-cell responses in the absence of any form of adjuvant. The multi-subunit quaternary structure of intact PDC was critical for this immunostimulatory activity because no response was produced by sensitization with monomeric recombinant PDC-E2 inner lipoyl domain. Mice sensitized with bPDC and CFA developed, within 2 weeks of sensitization, high-titer antibody responses reactive with bPDC that were fully cross-reactive with the murine homologue. Breakdown of T-cell tolerance to self-PDC took significantly longer, not being seen until 20 weeks postsensitization; a similar length of time to that previously shown to be required for EAC lesion development. Conclusions drawn from these data may have important implications for our understanding, and therapeutic manipulation, of PBC in humans.

Animals↗