Antigen-specificity of antibodies bound to glomeruli of mice with systemic lupus erythematosus-like syndromes

Abstract

Background: MRL/l mice with diffuse proliferative glomerulonephritis, and graft-versus-host (GVH) mice with membranous glomerulonephritis, are both regarded as models for human systemic lupus erythematosus. In these two models, the specificity of the nephritogenic antibodies was analyzed.

Experimental design: The nephritogenic antibodies were eluted from isolated glomeruli with an acid buffer. The antibodies were purified from these eluates on protein-A sepharose under high salt conditions to exclude the presence of antigens potentially bound to the antibodies. The specificities of the antibodies were analyzed towards components of the glomerular basement membrane (GBM), nuclear antigens and brush border of proximal epithelial cells in the indirect immunofluorescence (IF), enzyme linked immunosorbent assay, and Crithidia luciliae assay. Furthermore, we studied the glomerular binding by IF and immunoelectron microscopy after intravenous injection of the eluted antibodies into control mice.

Results: Glomerular eluates of both MRL/l and GVH mice showed nuclear staining and linear to homogeneous binding to GBM and tubular basement membrane in IF on normal mouse kidney. In enzyme linked immunosorbent assay, both eluates reacted not only with DNA, but also with histones and laminin, an important component of the GBM, however not with brush border. Reactivity with dsDNA was also found in the Crithidia luciliae assay for both eluates. In vivo binding was determined by injection of eluates into control MRL/n and F1 hybrid mice. The GVH eluate showed linear to homogeneous binding to the GBM 1.5 hour after injection which changed into a granular, membraneous pattern after 5 days, as determined by IF and immunoelectron microscopy. The MRL/l eluate also demonstrated linear to homogeneous binding to the GBM 1.5 hour after intravenous injection, that had decreased after 5 days, but did not change into a granular pattern.

Conclusions: In these two models of systemic lupus erythematosus nephritis not only antibodies to DNA and histones, but also antibodies to laminin are involved in the induction of murine systemic lupus erythematosus nephritis. The latter antibody specificity has not been identified before in renal or glomerular eluates obtained from diseased MRL/l mice.