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Chen RC, Naiyanetr P, Shu SA, Wang J, Yang GX, Thomas PK, Guggenheim KC, Butler JD, Bowlus C, Tao MH, Kurth MJ, Ansari AA, Kaplan M, Coppel RL, Lleo A, Gershwin ME, Leung PS. Antimitochondrial antibody heterogeneity and the xenobiotic etiology of primary biliary cirrhosis. Hepatology 2013; 57. [PMID: 23184636 PMCID: PMC3601563 DOI: 10.1002/hep.26157] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
UNLABELLED Antimitochondrial antibodies (AMAs) directed against the lipoyl domain of the E2 subunit of pyruvate dehydrogenase (PDC-E2) are detected in 95% of patients with primary biliary cirrhosis (PBC) and are present before the onset of clinical disease. The recent demonstration that AMAs recognize xenobiotic modified PDC-E2 with higher titers than native PDC-E2 raises the possibility that the earliest events involved in loss of tolerance are related to xenobiotic modification. We hypothesized that reactivity to such xenobiotics would be predominantly immunoglobulin M (IgM) and using sera from a large cohort of PBC patients and controls (n = 516), we examined in detail sera reactivity against either 6,8-bis(acetylthio) octanoic acid (SAc)-conjugated bovine serum albumin (BSA), recombinant PDC-E2 (rPDC-E2) or BSA alone. Further, we also defined the relative specificity to the SAc moiety using inhibition enzyme-linked immunosorbent assay (ELISA); SAc conjugate and rPDC-E2-specific affinity-purified antibodies were also examined for antigen specificity, isotype, and crossreactivity. Reactivity to SAc conjugates is predominantly IgM; such reactivity reflects a footprint of previous xenobiotic exposure. Indeed, this observation is supported by both direct binding, crossreactivity, and inhibition studies. In both early and late-stage PBC, the predominant Ig isotype to SAc is IgM, with titers higher with advanced stage disease. We also note that there was a higher level of IgM reactivity to SAc than to rPDC-E2 in early-stage versus late-stage PBC. Interestingly, this finding is particularly significant in light of the structural similarity between SAc and the reduced form of lipoic acid, a step which is similar to the normal physiological oxidation of lipoic acid. CONCLUSION Specific modifications of the disulfide bond within the lipoic-acid-conjugated PDC-E2 moiety, i.e., by an electrophilic agent renders PDC-E2 immunogenic in a genetically susceptible host.
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Affiliation(s)
- Richy C.Y. Chen
- Division of Rheumatology/Allergy and Clinical Immunology, University of California, Davis, CA 95616
| | - Phornnop Naiyanetr
- Division of Rheumatology/Allergy and Clinical Immunology, University of California, Davis, CA 95616,Department of Immunology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand
| | - Shang-An Shu
- Division of Rheumatology/Allergy and Clinical Immunology, University of California, Davis, CA 95616
| | - Jinjun Wang
- Division of Rheumatology/Allergy and Clinical Immunology, University of California, Davis, CA 95616
| | - Guo-Xiang Yang
- Division of Rheumatology/Allergy and Clinical Immunology, University of California, Davis, CA 95616
| | - P. Kenny Thomas
- Division of Rheumatology/Allergy and Clinical Immunology, University of California, Davis, CA 95616
| | | | | | | | - Mi-Hua Tao
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
| | - Mark J. Kurth
- Department of Chemistry, University of California, Davis, CA 95616
| | - Aftab A. Ansari
- Department of Pathology, Emory University School of Medicine, Atlanta, Georgia 30322
| | - Marshall Kaplan
- Department of Medicine, Division of Gastroenterology, New England Medical Center, Tufts University School of Medicine, Boston, MA 02111
| | - Ross L. Coppel
- Department of Medical Microbiology, Monash University, Melbourne, Australia
| | - Ana Lleo
- Center for Autoimmune Liver Diseases, Humanitas Clinical and Research Center, Rozzano (Milan), Italy
| | - M. Eric Gershwin
- Division of Rheumatology/Allergy and Clinical Immunology, University of California, Davis, CA 95616
| | - Patrick S.C. Leung
- Division of Rheumatology/Allergy and Clinical Immunology, University of California, Davis, CA 95616
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