Experimental glomerulonephritis induced by antigen that binds to glomerular fibronectin.

In previous studies we demonstrated that antigens with the capacity to bind to the glycoprotein fibronectin (FN), localized in the glomerular mesangium after intravenous (IV) injection. In the present study we sought to determine if the localization of FN-binding antigens in the mesangium is capable of inducing glomerulonephritis. A group of rats were injected IV with the FN-binding antigen phenylated gelatin (DNP-GL) followed 2 hours later by rabbit anti-DNP antibodies. This experimental protocol resulted in the development of a glomerulonephritis characterized by an initial heterologous phase and a late autologous phase. Both phases of the disease were characterized by significant histologic changes, including focal segmental mesangial matrix expansion, inflammatory cell infiltration, and an increase in endothelial and mesangial cells. By immunoperoxidase we demonstrated mesangial deposition of rabbit IgG and rat C3 during the initial heterologous phase and mesangial deposition of rat IgG and C3 during the autologous phase. Significant proteinuria developed during the heterologous phase, but not during the autologous phase of the disease. By contrast, rats injected with DNP-GL alone or anti-DNP antibodies alone did not develop significant histologic glomerular changes or proteinuria. In conclusion, antigens that bind to mesangial FN are capable of inducing glomerulonephritis. This mechanism of localization of antigens in the glomeruli may be relevant to human immune complex (IC)-mediated diseases involving antigens that have the capacity to bind to FN.