A system for accurate immunolocalization of Tamm-Horsfall protein in renal biopsies.

The distribution of Tamm-Horsfall protein (THP) was studied in the human kidney using formalin-fixed, paraffin-embedded sections with a monoclonal antibody specific for human THP applied in conjunction with a modified dinitrophenyl hapten sandwich staining (DHSS) procedure. The method was found to be highly sensitive producing very strong specific staining at antibody dilutions up to 1 in 64 000. Counterstaining with Haematoxylin and Eosin was possible without significant masking of the specific staining. This provided excellent structural definition of the background tissue which proved especially important in the study of THP localization in randomly oriented biopsy material. THP was found in all segments of the thick ascending limbs of loops of Henle, most segments of distal convoluted tubules and occasionally in distended collecting ducts and in the glomerular capsular space. Maculae densae did not contain THP. The combination of the modified DHSS procedure and the human THP specific antibody represents a highly sensitive and reliable method for specific staining of the THP in kidney sections.