title: V region gene analysis of human IgM hybridoma monoclonal anti-Sm antibodies.
abstract: Anti-Sm antibodies although highly specific for systemic lupus erythematosus can only be found in 10-25% of lupus patients and lupus-prone MRL/lpr mice. Molecular studies of these autoantibodies from mice have suggested that the anti-Sm response is Ag driven, its expression is controlled by stochastic events and may originate from the same B cell precursors as anti-DNA antibodies. However, relatively little information regarding the molecular characteristics of anti-Sm antibodies in man has been reported. We studied the V region genes of three IgM hybridoma monoclonal antibodies (BUD 45.12.8, BUD 114.4.11 and BUD 94.91.8) which were selected for Sm reactivity and derived from B cells of a healthy child. Two of these antibodies BUD 45.12.8 and BUD 114.4.11 also-reacted with ssDNA, while the third (BUD 94.91.8) did not. Each of these anti-Sm/ RNP antibodies was encoded by different and predominantly unmutated Ig heavy chain germline genes (BUD 45.12.8 by VH3-23, DXP4 and JH4b; BUD 94.91.8 by VH3-33, D21-9 and JH6b; BUD 114.4.11 by VH1-2, DK1 or DM1 or unknown D and JH4b) and light chain genes (BUD 45.12.8 by Humkv325 and JK2; BUD 94.91.8 by hsiggll150 (lambda IIIb) and J lambda 2/3; BUD 114.4.11 by Humk18 and JK3). Many of these genes are also used by antibodies with other specificities including DNA. The two anti-Sm antibodies which also bound ssDNA shared an overall V region net positive charge, while the third antibody without ssDNA reactivity carried a negative V region net charge. These findings demonstrate that (1) normal individuals have the genetic potential to generate autoantibodies to Sm/RNP; (2) acquisition of Sm/RNP binding is not dependent on somatic mutations and (3) some human B cell clones exhibit specificity for Sm and ssDNA.
authors.affiliation: Department of Medicine, University of Western Ontario, London Health Sciences Centre, Canada.
authors.forename: M
authors.initials: M
authors.lastname: Mahmoudi
authors.forename: J Y
authors.initials: JY
authors.lastname: Edwards
authors.forename: D A
authors.initials: DA
authors.lastname: Bell
authors.forename: E
authors.initials: E
authors.lastname: Cairns
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000974:Antibodies, Antinuclear / Q000235:genetics / Q000276:immunology; D000911:Antibodies, Monoclonal / Q000235:genetics* / Q000276:immunology; D000918:Antibody Specificity; D001324:Autoantigens / Q000276:immunology*; D001483:Base Sequence; D017931:DNA Primers; D004277:DNA, Single-Stranded / Q000276:immunology; D006801:Humans; D006825:Hybridomas / Q000166:cytology; D007143:Immunoglobulin Heavy Chains / Q000235:genetics; D007147:Immunoglobulin Light Chains / Q000235:genetics; D007075:Immunoglobulin M / Q000235:genetics* / Q000276:immunology; D007135:Immunoglobulin Variable Region / Q000235:genetics* / Q000276:immunology; D051379:Mice; D019463:Mice, Inbred MRL lpr; D008969:Molecular Sequence Data; D017411:Ribonucleoproteins, Small Nuclear / Q000276:immunology; D055517:snRNP Core Proteins
chemical_list: D000974:Antibodies, Antinuclear; D000911:Antibodies, Monoclonal; D001324:Autoantigens; D017931:DNA Primers; D004277:DNA, Single-Stranded; D007143:Immunoglobulin Heavy Chains; D007147:Immunoglobulin Light Chains; D007075:Immunoglobulin M; D007135:Immunoglobulin Variable Region; D017411:Ribonucleoproteins, Small Nuclear; D055517:snRNP Core Proteins