V region sequences of an idiotypically connected family of pathogenic anti-DNA autoantibodies

The H and L chain V region sequences of nine anti-DNA mAb that are representative of a pathogenic population of autoantibodies produced by the nephritis prone (SWR x NZB)F₁ (SNF₁) mice, were determined. These nine anti-DNA autoantibodies were idiotypically connected members of a cross-reactive Id family called the Id564 cluster. Moreover, these autoantibodies were all cationic in charge, IgG2b in isotype, and their H chain C regions had the normal SWR parent's allotype. Although derived from two different SNF₁ animals, these pathogenic autoantibodies possessed highly homologous Leader-V(H) sequences that could account for their idiotypic cross-reactivity. Furthermore, the V(H) region sequences of these anti-DNA antibodies contained numerous basic residues that could impart their cationic charge. The Leader-V(H) sequences of these autoantibodies were also highly homologous to that of an anti-NP antibody-related germ-line gene of C57BL/6 mice, called VH-23. Among these nine pathogenic autoantibodies, three sets of clonally related anti-DNA antibodies could be identified. Thus the Id564 cluster of cationic anti-DNA autoantibodies of SNF₁ mice are encoded by highly related V(H) genes, and this idiotypically connected population of pathogenic autoantibodies are selected to undergo an oligoclonal expansion in the lupus-prone SNF₁ mice.