The causes of primary biliary cirrhosis: Convenient and inconvenient truths

Primary biliary cirrhosis following Lactobacillus vaccination for recurrent vaginitis

BACKGROUND/AIMS

Antimitochondrial antibodies directed against the E2 subunit of the pyruvate dehydrogenase complex, PDC-E2, and other mitochondrial 2-oxoacid dehydrogenases (AMA-M2) are the hallmark for diagnosis of primary biliary cirrhosis (PBC). AMA-M2 formation as an early step in the pathogenesis of PBC has recently been assumed to be triggered by bacterial mimics of the E2 subunit and certain reactant xenobiotics. We report a case of symptomatic PBC diagnosed after sequential immunization with a lactobacillus vaccine for recurrent vaginitis over years.

METHODS

Serum AMA-M2 specificity of the patient was evaluated by indirect immunofluorescence, immunoblotting and ELISA. Serum antibody responses against pyruvate dehydrogenase complex-E2 subunit (PDC-E2(212-226)), the major PBC-specific mitochondrial autoepitope, and microbial mimics revealed cross-reactivity with beta-galactosidase of Lactobacillus delbrueckii (LACDE BGAL(266-280)) which shows a high local homology with that of Lactobacillus species administered via the vaccine. The relative affinity of antibody reactivity to LACDE BGAL(266-280) was significantly higher than that against human PDC-E2(212-226).

CONCLUSIONS

We conclude that lactobacillus vaccination therapy may be another culprit for the development of PBC in genetically susceptible women.

Loss of tolerance in C57BL/6 mice to the autoantigen E2 subunit of pyruvate dehydrogenase by a xenobiotic with ensuing biliary ductular disease

There have been important advances in defining effector mechanisms for several human autoimmune diseases. However, for most human autoimmune diseases, the induction stage is less well defined and there are very few clues on etiology. Our laboratory has focused on defining the molecular basis of autoantibody recognition and epitope modification in primary biliary cirrhosis (PBC). Our work has demonstrated that antibodies to mitochondria, the hallmark of disease, are directed against a very conserved site of pyruvate dehydrogenase, the E2 subunit of pyruvate dehydrogenase (PDC-E2). We have also demonstrated that several chemical xenobiotics, chosen based on quantitative structural activity relationship analysis and rigorous epitope analysis, when coupled to the lysine residue that normally binds the lipoic acid cofactor of PDC-E2, reacts as well or better to PBC sera than native autoantigen. In the present studies, we immunized C57BL/6 mice with one such xenobiotic, 2-octynoic acid, coupled to bovine serum albumin and we followed the mice for 24 weeks. Animals were studied for appearance of histologic lesions as well as appearance of antibodies to PDC-E2, serum levels of tumor necrosis factor-alpha and interferon-gamma, and splenic and liver lymphoid phenotyping by flow cytometry. Mice immunized with 2-octynoic acid manifest autoimmune cholangitis, typical mitochondrial autoantibodies, increased liver lymphoid cell numbers, an increase in CD8(+) liver infiltrating cells, particularly CD8(+) T cells that coexpress CD44, and finally an elevation of serum tumor necrosis factor-alpha and interferon-gamma.

CONCLUSION

these data provide a persuasive argument in favor of an environmental origin for human PBC.

New insights into autoimmune liver diseases

Autoinflammatory liver disease represents an important aspect of global hepatological practice. The three principal disease divisions recognized are autoimmune hepatitis, primary sclerosing cholangitis and primary biliary cirrhosis. Largely, but not exclusively, these diseases are considered to be autoimmune in origin. Increased recognition of outlier and overlap syndromes, changes in presentation and natural history, as well as the increased awareness of IgG4-associated sclerosing cholangitis, all highlight the limitations of the classic terminology. New insights continue to improve the care given to patients, and have arisen from carefully conducted clinical studies, therapeutic trials, as well as genetic and laboratory investigations. The challenges remain to treat patients before liver injury becomes permanent and to prevent the development of organ failure.

Autoantibodies in primary sclerosing cholangitis

The aetiology of primary sclerosing cholangitis (PSC) is not known and controversy exists as to whether PSC should be denominated an autoimmune disease. A large number of autoantibodies have been detected in PSC patients, but the specificity of these antibodies is generally low, and the frequencies vary largely between different studies. The presence of autoantibodies in PSC may be the result of a nonspecific dysregulation of the immune system, but the literature in PSC points to the possible presence of specific antibody targets in the biliary epithelium and in neutrophil granulocytes. The present review aims to give an overview of the studies of autoantibodies in PSC, with a particular emphasis on the prevalence, clinical relevance and possible pathogenetic importance of each individual marker.

Etiopathogenesis of primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is an autoimmune disease of the liver characterized by progressive bile duct destruction eventually leading to cirrhosis and liver failure. The serological hallmark of the disease is the presence of circulating antimitochondrial antibodies (AMA). These reflect the presence of autoreactive T and B cells to the culprit antigens, the E2 subunits of mitochondrial 2-oxo-acid dehydrogenase enzymes, chiefly pyruvate dehydrogenase (PDC-E2). The disease results from a combination of genetic and environmental risk factors. Genetic predisposition is indicated by the higher familial incidence of the disease particularly among siblings and the high concordance rate among monozygotic twins. Environmental triggering events appear crucial to disrupt a pre-existing unstable immune tolerance of genetic origin allowing, after a long latency, the emergence of clinical disease. Initiating mimotopes of the vulnerable epitope of the PDC-E2 autoantigen can be derived from microbes that utilize the PDC enzyme or, alternatively, environmental xenobiotics/chemical compounds that modify the structure of native proteins to make them immunogenic. A further alternative as a source of antigen is PDC-E2 derived from apoptotic cells. In the effector phase the biliary ductular cell, by reason of its proclivity to express the antigen PDC-E2 in the course of apoptosis, undergoes a multilineage immune attack comprised of CD4⁺ and CD8⁺ T cells and antibody. In this article, we critically review the available evidence on etiopathogenesis of PBC and present interpretations of complex data, new developments and theories, and nominate directions for future research.

A tribute to an outstanding immunologist - Ian Reay Mackay

The 11th Australasian Autoimmunity Workshop was held in Melbourne, Australia from July 6-8, 2007 organized by the Monash University Autoimmunity Network. The workshops, founded by the late Kevin Lafferty, are a chance for Australasians interested in research into autoimmune disease to present and discuss their work. This workshop also was a chance to acknowledge Ian Mackay, a pioneer clinician-scientist who has made major contributions to our understanding of autoimmune diseases. Friends, colleagues and former students attended the Workshop and acknowledged Ian's expertise and mentorship. This edition of the Journal of Autoimmunity pays tribute to Ian Mackay. It features articles from attendees at the workshop, and contributions from some of Ian's past students and past and current collaborators.

Antimitochondrial antibody-negative primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is considered a classic autoimmune disease insofar as 95% of patients are seropositive for specific antimitochondrial antibodies (AMA). Yet it is still the case that the remaining 5% of patients have equivalent disease but test persistently AMA negative. Although variations exist in the immunologic profile of these patients, clinically there are no discernable differences, and although the diagnostic threshold is higher, the treatment and prognosis mirror that of classic disease. Previous terminology, therefore, has been abandoned in favor of the description, AMA-negative PBC.