Immunohistochemical and lectin dissection of the human nephron in health and disease.

Many renal diseases involving the tubular epithelium appear to preferentially affect certain nephron segments. While major portions of the nephron, such as proximal and distal convoluted tubules and collecting ducts, can be identified in the normal kidney, the distinction of diseased nephron segments can be difficult in tissue sections. Thus, to identify which nephron segments are involved in pathologic changes is usually impossible by routine histologic examination alone. Recently antibody and lectin probes that react with specific nephron segment-specific epitopes and carbohydrates, respectively, have become available. Some of these antibodies and lectins can be used on formalin-fixed, paraffin-embedded, archival tissues. Because renal tubules appear to retain their nephron segment-specific epitopes and glycoprotein moieties under most pathologic conditions, these nephron segment-specific tubular epithelial markers provide a method to study renal diseases involving the tubular system also in archival material. Such nephron segment-specific tubular epithelial markers are: the lectins, Tetragonolobus purpuras and Phaseolus vulgaris erythroagglutinin (proximal tubular markers); antibodies to low-molecular-weight cytokeratin (AE1/AE3); epithelial membrane antigen and the lectin Arachis hypogaea (distal nephron [distal convoluted tubule and collecting duct] markers); and antibodies to Tamm-Horsfall protein (labeling the thick ascending limb of Henle). We review the application of these and other renal tubular epithelial markers in the normal kidney and in various renal diseases including cystic disease of the kidney, interstitial nephritis, tubular atrophy, acute tubular necrosis, myeloma cast nephropathy, and renal tumors.