title: The role of clonal selection and somatic mutation in autoimmunity.
abstract: Polyclonal activation has been proposed as the reason that autoantibodies are produced during autoimmune disease. This model denies a role for specific antigen selection of B cells and predicts instead a multiclonal population of unmutated or randomly mutated autoantibodies. We have found that the genetic features and clonal composition of spontaneously derived immunoglobulin G (IgG) antiself-IgG (rheumatoid factor (RF] autoantibodies derived from the autoimmune MRL/lpr mouse strain are inconsistent with both the predictions of this model and the actual outcome of experimental polyclonal activation. Instead we have found that MRL/lpr RFs are oligoclonal or even monoclonal in origin. They harbour numerous somatic mutations which are distributed in a way that suggests immunoglobulin-receptor-dependent selection of these mutations. In this sense, the MRL/lpr RFs resemble antibodies elicited by exogenous antigens after secondary immunization. The parallels suggest that, like secondary immune responses, antigen stimulation is important in the generation of MRL/lpr RFs.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001323:Autoantibodies / Q000235:genetics*; D001324:Autoantigens / Q000276:immunology; D001327:Autoimmune Diseases / Q000235:genetics*; D001402:B-Lymphocytes / Q000276:immunology; D001483:Base Sequence; D002999:Clone Cells / Q000276:immunology; D006825:Hybridomas / Q000276:immunology; D007074:Immunoglobulin G / Q000235:genetics; D008213:Lymphocyte Activation; D051379:Mice; D008807:Mice, Inbred BALB C; D008809:Mice, Inbred C3H; D009154:Mutation; D012217:Rheumatoid Factor / Q000235:genetics
chemical_list: D001323:Autoantibodies; D001324:Autoantigens; D007074:Immunoglobulin G; D012217:Rheumatoid Factor