Experimental membranous glomerulonephritis in rats induced with gp 700, a glomerular protein

To investigate the antigenicity of glomerular cell products for the induction of Heymann nephritis (HN), eight Lewis rats were immunized with an isolated glomerular protein (GLP) with only limited tubular cell contamination. Four out of four rats immunized with 240 micrograms GLP showed proteinuria at week 12. Their kidney specimens taken at week 16 showed contiguous granular deposits of IgG along the glomerular basement membrane by direct immunofluorescence and corresponding electron-dense deposits; the findings were identical to those in classical HN induced by the brush border protein. By immunoprecipitation, IgG eluted from isolated glomeruli of rats that received 240 micrograms GLP precipitated only a 700 kd glycoprotein (gp 700) in GLP, whereas 330, 440, and 700 kd glycoproteins were precipitated in the crude preparation (Fx1A), which is derived mainly from renal tubules. Two different monoclonal antibodies (anti-gp 330 and 14C1) against gp 330 precipitated the antigens in the same fashion as the glomerular eluate. These data reveal that gp 700, gp 440, and gp 330 share epitopes and that the gp 700 is demonstrable both in the glomerulus and in tubular brush border but that gp 440 and gp 330 are present only in the brush border. In addition, glomerular gp 700 was shown to induce Heymann-type glomerulonephritis just as gp 330 did.