The development and resolution of glomerular basement membrane changes associated with subepithelial immune deposits

The morphogenesis of glomerular basement membrane changes associated with subepithelial immune deposits was studied in kidney biopsies from patients with gold-induced membranous glomerulonephoritis. Serial biopsies showed focal accumulations of additional basement membrane material around the deposits, suggesting that the deposited material stimulated the epithelium to increased synthesis. Moreover, the deposits were gradually displaced towards the inner (endothelia) side of the basement membrane during the course of the disease, suggesting that this layer undergoes a slow continuous turnover, with removal at its endothelial aspect. The two processes--increased epithelial synthesis and turnover--are suggested to constitute the basis of a natural healing process resulting in elimination of the deposits and structural restoration of the basement membrane. The epithelial slit membranes were dislocated externally by the deposits or the excessive basement membrane material, indicating that their barrier function is preserved even in this pathologic condition.