Relationships among the histologic pattern, intensity, and phenotypes of t cells infiltrating renal allografts

The evaluation of renal allograft rejection by routine histologic evaluation of transplant biopsy is often a diagnostic problem. Advances in monoclonal antibody and immunohistochemical technology have led to their application in characterizing the phenotype of peripheral blood lymphocytes in transplant recipients, as well as the infiltrating lymphocytes in renal biopsy specimens (both tissue and aspiration cytology samples). Recent reports suggest that the relative number of infiltrating T cells and the T cell phenotypic subset ratio may have some association with graft survival. However, most allograft biopsy studies have not examined the relationship of the intensity and phenotype of T cells to the histologic pattern of infiltration, while fine-needle aspiration cytology (FNAC) and peripheral blood analysis do not allow for this assessment. To examine the association of histologic pattern with the intensity and phenotype of T cell infiltrates, immunoperoxidase labeling of cells using monoclonal antibodies was evaluated in 66 renal allograft biopsies performed because of clinical suspicion of rejection. Our findings indicate that the ratio of T helper-inducer (Leu 3) cells to T suppressor-cytotoxic (Leu 2) cells is significantly lower in the pattern of diffuse renal cortex infiltration (cortical diffuse [CD] pattern) when compared with other histologic patterns (cortical aggregate or perivascular), regardless of the overall intensity of the T cell infiltrate. A significant difference in T cell phenotypes was also found among different histologic patterns as expressed by Leu 3/Leu 2 ratios and by the number of Leu 2 cells. An increase in the overall intensity of T cell infiltrate was not associated with significant changes in T cell phenotype seen in any pattern, but an increase in the intensity of the cortical diffuse T cell infiltrate was associated with a significant decrease in the Leu 3/Leu 2 ratio (P <0.04), which was due to an increase in the population of Leu 2 cells (P <0.002). Interestingly, increases in the intensity of either cortical aggregate or perivascular T cell infiltrates were associated with significant increases in both Leu 3 and Leu 2 cells, as well as a tendency towards higher Leu 3/Leu 2 ratios. These findings indicate that evaluation of T cell infiltrates by phenotype in renal allografts is dependent upon the pattern as well as the intensity of infiltrate.