Isolation of a 330-kDa glycoprotein from human kidney similar to the Heymann nephritis autoantigen (gp330)

Because of the similarities between Heymann nephritis of rat and human membranous glomerulonephritis, we searched for a protein in human kidney similar to that of the putative autoantigen of Heymann nephritis, gp330. Human gp330 was isolated by a purification scheme identical to that used for the isolation of rat gp330. The isolated human gp330 was compared with rat gp330 by peptide mapping and was found to be very similar in structure. Studies of immunologic reactivity of the rat antigen-induced Heymann nephritis nephritogenic autoantibody to human gp330 indicated that some of the rat antigen epitopes were shared with its human counterpart. The human gp330 was capable of eliciting on active Heymann nephritis response in rats when used as an immunogen. The nephritogenic autoantibody eluted from these rat kidney glomeruli showed equal binding to both rat and human antigens. Finally, a polyclonal antibody to human gp330 was able to induce passive Heymann nephritis in rats. These results demonstrate that there is a gp330 protein in human kidney that is very similar to the putative autoantigen of Heymann nephritis.