An approach to immunomicroscopy of renal disease with immunoperoxidase and periodic acid-Schiff counterstain (IMPAS stain).

A series of 127 renal specimens reflecting a wide spectrum of renal pathology was evaluated with a direct immunoperoxidase technic in which frozen tissue was first reacted with anti-Ig(G,A,M) and anti-C3-peroxidase conjugates and subsequently counterstained with periodic acid-Schiff-hematoxylin (IMPAS). This technic permitted simultaneous evaluation of light-microscopic changes and yielded a permanent immunomicroscopic record. Frequently, a distinction could be made between epimembranous, intramembranous and subendothelial deposits, which was not possible using immunofluorescence. The findings were correlated with histologic, immunofluorescent and electron-microscopic results. General patterns of immune complex and autoantibody deposition were similar in 124 cases. In one case, there was poor correlation between results obtained by immunoperoxidase and immunofluorescence. In two other cases, deposits detected by electron microscopy were not identified by either immunoperoxidase or immunofluorescence. The IMPAS stain, combining immunomicroscopy with conventional light microscopy, may be a useful approach to the laboratory diagnosis of renal disease.