Independently derived murine glomerular immune deposit-forming anti-DNA antibodies are encoded by near-identical V_H gene sequences

To examine the influence of variable region sequences on the capacity of individual lupus autoantibodies (autoAb) to form glomerular immune deposits, the complete V_H and V_L region sequences of three anti-DNA mAb that produced morphologically similar immune deposits after administration to normal mice were determined. The Ig were independently derived from 1-mo-old (H238, IgM), 3-mo-old (H8, IgG2a), and 6-mo-old (H161, IgG3) MRL-lpr/lpr mice, and they all produced subendothelial and mesangial immune deposits after passive transfer to normal mice. In addition, H238 and H161 produced granular deposits in small extraglomerular vessels. The mAb had nearly identical V_H gene sequences; H8 differed from H238 and H161 by a single nucleotide in FR1 that resulted in a histidine for glutamine substitution. This V_H gene sequence was also > 99% homologous to another anti-DNA Ab (termed H241), that we previously reported to produce glomerular immune deposits in a similar morphologic pattern. H161 and H238 were encoded by DFL16 and J_H2 genes, whereas H8 was encoded by a J_H4 gene. Different V_k family genes were used to encode the three mAb, however H161 and H238 both used a J_k5 gene. The results indicate that an identical or highly related V_H gene is used to encode a subgroup of murine lupus autoAb that share immune deposit forming properties. Furthermore, they raise the possibility that amino acid residues independent from those encoded by V_H genes may be influential in immune deposit formation at extraglomerular sites.