Biochemical investigation of the pathogenesis of Heymann nephritis

This study describes biochemical comparison of proximal tubule antigens from the brush border membrane (BBM) of dog and rat kidney. The purpose was to determine if a difference in BBM composition could explain the inability to produce either active or passive Heymann Nephritis in the dog. Although the membrane composition as revealed by coomassie blue staining on 4 to 11 per cent polyacrylamide electrophoresis varied considerably between rats and dogs, polyclonal antibodies (rabbit anti-rat, rabbit anti-dog) against purified BBM from both species immunoprecipitated five identical polypeptides. Four bands were visualized between 70 kd and 170 kd; but the major polypeptide had an apparent molecular wt of approximately 460 kd. This high molecular wt constituent and three of the other peptides were bound specifically to lentil lectin column, confirming their glycoprotein nature. Only the 460 kd polypeptide was immunoprecipitated by monoclonal antibody against gp 330. Since both rat and dog BBM contain gp 330, believed to be the sole pathogenic antigen in Heymann Nephritis, we conclude that failure to produce active or passive Heymann Nephritis in the dog using the same protocol that is successful in rats cannot be attributed to differences in antigenic make-up of the brush border membrane.