The objectives of this research are: 1) To purify and characterize the sialoglycoprotein nephritogenic antigens by chromatography, electrophoresis, histochemistry, electron-microscopy, amino acid and carbohydrate analysis. 2) To prepare monospecific antibodies against these antigens by the Carrageenan double diffusion method and utilize such antibodies for antigen localization studies. 3) To compare by in vitro and in vivo methods the affinity of different nephritis producing compounds for the glomerulus and for the purified nephritogenic antigens. 4) To investigate the pathogenetic mechanism of enhancement of glomerular damage, produced by haptenic glomerular preparations in conjunction with the nephrotoxic serum.