Characterization and in vivo transfer of nephritogenic autoantibodies directed against dipeptidyl peptidase IV and laminin in experimental lupus nephritis.

The present studies dealt with the pathogenesis of renal involvement in murine chronic graft-versus-host disease, which is a model for human systemic lupus erythematosus. The disease was induced in (C57BL10xDBA/2)F1 hybrids by injection of DBA/2 lymphocytes. The animals developed systemic disease accompanied by deposition of autoantibodies in the glomeruli and a lupus type of nephritis. Antibodies were eluted from glomeruli isolated during various stages of the disease by magnetic extraction from iron-perfused kidneys. For assessment of the specificity of the antibodies, we used indirect immunofluorescence, an enzyme-linked immunosorbent assay, and immunoblotting. In glomeruli from week 4, autoantibodies were found to be directed against several antigens, among which were the glomerular basement membrane component laminin and the glomerular enzyme dipeptidyl peptidase IV, whereas week 8 glomeruli also showed antibodies directed against nuclear antigens. Both laminin and dipeptidyl peptidase IV are known nephritogenic antigens occurring in renal tubular epithelial brush border preparations. Antibodies eluted from isolated glomeruli of diseased animals bound in a granular pattern along the glomerular capillary wall after in vivo transfer. Anti-renal tubular epithelial antibodies in the sera of diseased animals were affinity purified and injected into naive mice, which induced immune complex glomerulonephritis and proteinuria, thus confirming the nephritogenic role of these autoantibodies in this model.