Antigenic targets in epimembranous glomerulonephritis. Experimental data and potential application in human pathology

Although membranous glomerulonephritis (MGN) has been long considered as a prototype of glomerulonephritis (GN) due to the deposition of circulating immune complexes (CIC), a growing body of evidence indicates that immune deposits can also be formed in situ and implicate antigens expressed by glomerular epithelial cells (GEC). Some of these antigens have recently been identified. The first one, gp330 - a 330-kd glycoprotein restricted to the coated pits of GEC and renal brush border (BB) - is responsible for Heymann nephritis, a rat model of MGN. However, it is absent in the human glomerulus and is therefore probably not involved in human cases of MGN, at least in those due to in situ formation of CIC. In addition, by raising monoclonal antibodies against rat and rabbit BB, we have isolated two other BB proteins also expressed on GEC. The latter, respectively identified as dipeptidyl peptidase IV (90 kd) and enkephalinase (85 kd), can serve as targets for the formation of short-lived immune deposits. Since they are also detected on human GEC, they might play a role in the pathogenesis of MGN in man.