SLA/LP/tRNP(Ser)Sec antigen in autoimmune hepatitis: Identification of the native protein in human hepatic cell extract

• Published in: Journal of autoimmunity 2010-02, Vol.34 (1), p.59-65
• Main Authors: Volkmann, Martin, Luithle, Daniel, Zentgraf, Hanswalter, Schnölzer, Martina, Fiedler, Sabine, Heid, Hans, Schulze-Bergkamen, Andrea, Strassburg, Christian P, Gehrke, Sven G, Manns, Michael P
• Format: Article
• Language: English
• Subjects: Allergy and Immunology; Amino Acid Sequence; Antibodies, Monoclonal - metabolism; Autoantigens - blood; Autoantigens - genetics; Autoantigens - immunology; Autoantigens - metabolism; Biological and medical sciences; Cell Extracts; Cell Line, Tumor; Chromatography, Affinity; Cloning, Molecular; Diagnosis; Fundamental and applied biological sciences. Psychology; Fundamental immunology; Gastroenterology. Liver. Pancreas. Abdomen; Hepatitis, Autoimmune - blood; Hepatitis, Autoimmune - diagnosis; Hepatitis, Autoimmune - immunology; Hepatitis, Autoimmune - metabolism; Hepatocytes - immunology; Hepatocytes - metabolism; Hepatocytes - pathology; Humans; Immunology; Inflammation; Liver; Liver. Biliary tract. Portal circulation. Exocrine pancreas; Mass Spectrometry; Medical sciences; Molecular Sequence Data; Other diseases. Semiology; Peptide Fragments - blood; Peptide Fragments - genetics; Peptide Fragments - immunology; Peptide Fragments - metabolism; Recombinant Proteins - blood; Recombinant Proteins - genetics; Recombinant Proteins - immunology; Recombinant Proteins - metabolism; RNA, Transfer, Amino Acyl - blood; RNA, Transfer, Amino Acyl - genetics; RNA, Transfer, Amino Acyl - immunology; RNA, Transfer, Amino Acyl - metabolism; Serology
• ISSN: 0896-8411; 1095-9157
• DOI: 10.1016/j.jaut.2009.07.005

Abstract A diagnostic subgroup of AIH type 1 is characterized by specific serum antibodies against soluble liver protein. The respective autoantigen was named SLA/LP/tRNP(Ser)Sec , after three homologous recombinant polypeptides were isolated from expression gene libraries. We analyzed human cultured liver cells for the human homologue of recombinant SLA/LP/tRNP(Ser)Sec by antigen purification. In addition, a monoclonal antibody was generated against recombinant SLA-p35, a truncated recombinant SLA-reactive polypeptide. With a positive patient serum, immune affinity chromatography was performed on the 52 kD-SLA main antigenic determinant pre-enriched by ion exchange chromatography. By mass spectrometry, the 52 kD-SLA/LP/tRNP(Ser)Sec autoantigen was unambiguously identified in the purification product. The identity of the recombinant SLA-p35 and its human homologue was further confirmed by a specific signal of the anti SLA-p35 monoclonal antibody with purified human SLA/LP/tRNP(Ser)Sec . The 48 kD-SLA species frequently comigrating in SLA-immunoblotting however was not identified by either approach. We conclude that the native counterpart of recombinant tRNP(Ser)(Sec) indeed is detectable with a molecular weight of 52 kD in soluble liver extract of human cells as the major antigenic component of SLA/LP/tRNP(Ser)Sec.