title: Serum SmD autoantibody proteomes are clonally restricted and share variable-region peptides.
abstract: Recent advances in mass spectrometry-based proteomic methods have allowed variable (V)-region peptide signatures to be derived from human autoantibodies present in complex serum mixtures. Here, we analysed the clonality and V-region composition of immunoglobulin (Ig) proteomes specific for the immunodominant SmD protein subunit of the lupus-specific Sm autoantigen. Precipitating SmD-specific IgGs were eluted from native SmD-coated ELISA plates preincubated with sera from six patients with systemic lupus erythematosus (SLE) positive for anti-Sm/RNP. Heavy (H)- and light (L)-chain clonality and V-region sequences were analysed by 2-dimensional gel electrophoresis and combined de novo database mass spectrometric sequencing. SmD autoantibody proteomes from all six patients with SLE expressed IgG1 kappa restricted clonotypes specified by IGHV3-7 and IGHV1-69 H-chains and IGKV3-20 and IGKV2-28 L-chains, with shared and individual V-region amino acid replacement mutations. Clonotypic sharing and restricted V-region diversity of systemic autoimmunity can now be extended from the Ro/La cluster to Sm autoantigen and implies a common pathway of anti-Sm autoantibody production in unrelated patients with SLE.
authors.affiliation: Department of Immunology, Flinders Medical Centre and Flinders University, SA Pathology, Bedford Park, 5042 South Australia, Australia.
authors.forename: Mahmood A
authors.initials: MA
authors.lastname: Al Kindi
authors.affiliation: Flinders Proteomic Facility, Flinders University, Australia.
authors.forename: Tim K
authors.initials: TK
authors.lastname: Chataway
authors.affiliation: Department of Immunology, Flinders Medical Centre and Flinders University, SA Pathology, Bedford Park, 5042 South Australia, Australia.
authors.forename: George A
authors.initials: GA
authors.lastname: Gilada
authors.affiliation: Department of Immunology, Flinders Medical Centre and Flinders University, SA Pathology, Bedford Park, 5042 South Australia, Australia.
authors.forename: Michael W
authors.initials: MW
authors.lastname: Jackson
authors.affiliation: Department of Immunology, Flinders Medical Centre and Flinders University, SA Pathology, Bedford Park, 5042 South Australia, Australia.
authors.forename: Fiona M
authors.initials: FM
authors.lastname: Goldblatt
authors.affiliation: Department of Immunology, Flinders Medical Centre and Flinders University, SA Pathology, Bedford Park, 5042 South Australia, Australia.
authors.forename: Jenny G
authors.initials: JG
authors.lastname: Walker
authors.affiliation: Flinders Proteomic Facility, Flinders University, Australia.
authors.forename: Alex D
authors.initials: AD
authors.lastname: Colella
authors.affiliation: Department of Immunology, Flinders Medical Centre and Flinders University, SA Pathology, Bedford Park, 5042 South Australia, Australia. Electronic address: t.gordon@flinders.edu.au.
authors.forename: Tom P
authors.initials: TP
authors.lastname: Gordon
mesh_terms: D000328:Adult; D000368:Aged; D000595:Amino Acid Sequence; D000974:Antibodies, Antinuclear / Q000235:genetics / Q000276:immunology; D001323:Autoantibodies / Q000097:blood / Q000235:genetics / Q000276:immunology*; D015180:Electrophoresis, Gel, Two-Dimensional; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000235:genetics / Q000276:immunology; D007135:Immunoglobulin Variable Region / Q000235:genetics / Q000276:immunology*; D008180:Lupus Erythematosus, Systemic / Q000097:blood / Q000235:genetics / Q000276:immunology; D013058:Mass Spectrometry; D008875:Middle Aged; D008969:Molecular Sequence Data; D009154:Mutation; D010455:Peptides / Q000235:genetics / Q000276:immunology*; D020543:Proteome / Q000235:genetics / Q000276:immunology*; D040901:Proteomics / Q000379:methods; D017386:Sequence Homology, Amino Acid; D055517:snRNP Core Proteins / Q000276:immunology*
chemical_list: D000974:Antibodies, Antinuclear; D001323:Autoantibodies; D007074:Immunoglobulin G; D007135:Immunoglobulin Variable Region; D010455:Peptides; D020543:Proteome; D055517:snRNP Core Proteins
keywords: Mass spectrometry; Public clonotypes; Sm autoantigen; Systemic lupus erythematosus