SEGMENTAL LOCALIZATION AND QUANTITATIVE CHARACTERISTICS OF TUBULITIS IN KIDNEY BIOPSIES FROM PATIENTS UNDERGOING ACUTE REJECTION

The term tubulitis denotes infiltration of the renal tubular epitheliu m by mononuclear cells. Tubulitis is one of the most reliable signs of acute renal allograft rejection. However, its segmental localization and quantitative characteristics are not precisely known. To investiga te this question, formalin-fixed kidney biopsy specimens from 15 patie nts with transplanted allografts undergoing acute rejection were studi ed stereologically by identifying cortical tubules with segment-specif ic markers. The periodic acid-Schiff reaction, peanut lectin, and anti bodies against Tamm-Horsfall protein and epidermal cytokeratins, all a pplied to the same section, were used to identify the profiles of prox imal tubules (PTs), distal convoluted tubules (DCTs), distal straight tubules (DSTs), and the cortical collecting system (CCS, connecting tu bules and cortical collecting ducts), respectively. Two parameters, th e relative intrasegmental length and the average intensity of tubular damage, were determined to describe the degree of tubulitis quantitati vely. Tubulitis was most prominent in the DCTs, followed by the CCS. T he average intensity of tubulitis was lowest in the DSTs. The results indicate that the PTs are not the main site of tubulitis, despite the fact that they are regarded primary targets of the rejection response.