Antibodies directed against tubular brush border antigens (RTE) are used to induce heterologous immune-complex nephritis. Among these antigens a glycoprotein with a molecular weight of 330 kilodaltons (gp330) has been shown to be of pathogenetic significance. We investigated whether antibodies other than those directed against gp330 are present in anti-RTE and whether they play a pathogenetic role. By using enzyme-linked immunosorbent assay techniques and Western blotting, we investigated polyclonal antibodies directed not only against crude RTE but also against RTEgp, a purified glycoprotein fraction of RTE, with respect to activity against glomerular basement membrane (GBM) components laminin, fibronectin, and type IV collagen. Both antibody preparations showed reactivity predominantly to the 220 kilodaltons subunit of laminin. Lower but nevertheless distinct reactivity to fibronectin and type IV collagen was also found. The antibody fraction directed against components of the GBM, which was isolated from anti-RTE IgG by affinity chromatography, showed linear binding to the GBM in indirect immunofluorescence studies. Injection of these antibodies into the renal artery also led to linear binding to the GBM with linear deposition of complement factors 3 and 9 and induced a weak and transient proteinuria. Immunoelectron microscopy revealed binding of the antibodies to glomerular epithelial and endothelial cell surfaces adjacent to the GBM. Injection of anti-RTE antibody absorbed to GBM components resulted in binding of antibodies and complement factors 3 and 9 in a fine granular pattern along the GBM, whereas injection of unabsorbed anti-RTE led to a course granular pattern. We conclude that the presence of antibodies (cross-)reacting with laminin, fibronectin, and type IV collagen in anti-RTE antibody has pathogenetic effects and could explain differences in pathogenicity between monospecific anti-gp330 antibody and polyclonal anti-RTE antibody.