Isolation and characterization of rat nephritogenic and non nephritogenic brush border antigens

Two kinds of brush border antigens were isolated from pronase-treated rat tubular material by gel filtration, DEAE-chromatography and disc-electrophoresis, successively. One, a 0.05 M antigen which was eluted from DEAE-column with 0.05 mol of NaCl solution, has no nephritogenic ability when inoculated into homologous rats. The other, a 0.30 M antigen eluted with 0.30 mol of NaCl solution, induces membranous nephritis when injected into rats. Immunoprecipitation studies show no common factor between these two antigens. SDS-polyacrylamide electrophoresis shows the molecular size of 0.05 M and 0.30 M antigens to be respectively over 200 kD and about 90 kD. Rabbit antiserum against the 0.05 M antigen fixed to the GBM in a diffuse granular fashion as well as to the brush border by immunofluorescence when incubated in vitro with normal rat kidney section. Rabbit antiserum to the 0.30 M antigen, however, fixed exclusively in vitro to the brush border. Passive transfer of nephritis was studied with these rabbit antisera. When antiserum to 0.05 M antigen was injected into normal rat, diffuse granular deposition of rabbit IgG was observed in the GBM within 2 h of the injection, but the deposits became negative 1 week later. Rats injected with antiserum to the 0.30 M antigen showed no glomerular deposition within 2 days but diffuse granular deposits of rabbit IgG were observed within 1 week and increased until 2 weeks after the injection. These facts should be considered in the studies on passive Heymann nephritis and its pathogenesis.