Antibodies binding to double-stranded (ds) DNA are strongly associated with renal involvement in patients with systemic lupus erythematosus (SLE). We have generated two new IgG DNA-binding monoclonal antibodies (mAb), RH-14 and DIL-6, from the peripheral blood lymphocytes of two SLE patients with glomerulonephritis using the heteromyeloma cell line CB-F7. RH-14 is an IgG1 Q antibody which also bound to single-stranded DNA, histones and nucleosomes. DIL-6 is an IgG3 Q antibody with restricted antigen binding specificity. cDNA encoding the variable regions of the heavy (V H) and light (V L) chains of RH-14 was sequenced and the antigen binding site of this mAb was computer modelled. Sequence analysis of V H and V L regions of RH-14 showed that V H is derived from germ-line gene V3-7, a member of the V H 3 family, and V L is derived from DPL 11, a member of the V Q 2 family. Somatic mutations and basic amino acid residues are identified in the complementarity-determining regions of both V H and V L regions. The nephritogenic properties of these mAb were analyzed by implanting and growing the hybridoma cells secreting the mAb in the peritoneum of SCID mice. The animals that received the RH-14 hybridoma produced higher levels of proteinuria (3 to n 4) (p X 0.001) compared to the groups that received DIL-6 (trace to n 1) or CB-F7 (trace). Electron microscopy of kidney sections from all the RH-14-implanted animals showed granular immunoglobulin deposition in the renal glomerular capillaries and mesan-gium. In this study we have shown for the first time using electron microscopy that a human IgG anti-dsDNA mAb, RH-14, is nephritogenic and that deposition of such an antibody alone is sufficient to induce renal damage.
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