RESUMO
Twenty-eight frozen renal biopsy specimens with a marked mononuclear cell interstitial infiltrate (MCI) were analyzed with monoclonal antibodies and a biotin-avidin peroxidase technique to define the surface phenotype distribution of the infiltrating cells. Twelve cases were diagnosed as tubulointerstitial nephritis of acute and chronic presentation, of unknown cause in 5 cases or secondary to multiple myeloma or drug reactions. Sixteen cases occurred in primary and secondary glomerulonephritis, 3 cases being associated with lymphoproliferative disorders. The results showed a remarkable heterogeneity of the MCI composition, even in cases with similar clinical and pathological findings. Namely, the T cells accounted for the majority of the infiltrating cells in most cases but a variable predominance of the T cell subsets Leu3 and Leu2 was observed. B cells and monocytes were also prominent in some cases. Such differences in the MCI composition may indicate the activation of different mechanisms of tissue damage, or a different phase of the renal disease. In the three cases of glomerulonephritis associated with lymphoproliferative disorders, the malignant origin of the MCI was demonstrated in one case, while in the remaining cases it was excluded.