Immunoexpression of perforin and granzyme B on infiltrating lymphocytes in human renal acute allograft rejection.

Graft destruction can be effected by direct cell-to-cell contact between activated effector T cell and a target graft resulting in delivery of cytotoxic molecules. Perforin and granzyme B can be used as activation markers for cytotoxic cells in allograft tissue. The aim of the study was to determine the immunoexpression of perforin and granzyme B by immune cells infiltrating renal tissue during acute allograft rejection and to evaluate any correlation between the phenotype of infiltrating lymphocytes and cells expressing cytotoxic granules as well as the severity of graft damage as defined by Banff 97 criteria. Immunoperoxidase staining was carried out using monoclonal antibodies anti-perforin, -granzyme B, -CD3 and -CD8 on renal allograft biopsy specimens from twenty one patients with acute renal transplant rejection: Banff 97 IA (n = 11) and Banff 97 IB (n = 10). As a control 11 biopsy specimens of renal transplant patient without any signs of rejection were used. All allograft biopsy specimens with acute renal transplant rejection contained a high number of CD3+ T cells (Banff IA: 437.4 +/- 154.4 and Banff IB: 825 +/- 339.9 vs 123.4 +/- 52.5 in controls) and CD8+ T lymphocytes (Banff 97 IA: 177.6 +/- 89.2 and Banff IB: 293.2 +/- 112.4 vs 64.2 +/- 37.1 in controls). Immunostaining for granzyme B and perforin was negative in controls. The immunopositivity for perforin was similar in Banff IA and Banff IB acute allograft rejection (1.5 +/- 0.6 vs 1.8 +/- 0.8, respectively). Granzyme B+ cell count was significantly higher in severe rejection group Banff IB (128.3 +/- 74.3) than in Banff IA group (48.2 +/- 18.3). Moreover, in acute allograft rejection Banff IB the number of granzyme B+ cells and perforin+ cells was correlated with the number of CD8+ T cells. In conclusion, our results suggest that in acute tubulointerstitial allograft rejection activated cytotoxic T lymphocytes play a major role. The strong immunopositivity for granzyme B on infiltrating cells in renal transplant tissue is suggested as a marker of severity of graft damage.