[Current topics of the rejection pathology in human renal allografts]

The topics of renal allograft pathology; validation of the Banff classification and a new criterion for chronic rejection are reviewed. Although the clinico-pathologic utility of the Banff classification is remarkably high in acute rejection, the Banff scheme is still incomplete. The severity of rejection based on the Banff schema well correlated with the deterioration of graft function and also with reversibility of the graft function. Grade III acute rejection in the Banff schema suggested poor graft function, while grade IIb acute rejection could be cured by rejection therapy in the CyA era. The morphological characteristics of chronic rejections in renal allografts become milder and less specific in the CyA era. The differentiation of chronic rejection of immunologic origin from other conditions leading to renal scarring remains one of the major problems in renal allograft biopsy interpretation. Chronic CyA nephrotoxicity and/or glomerulonephritis frequently accompany chronic rejection. Electron microscopic peritubular capillary basement membrane lesion (MSPTC) was a sensitive indicator for chronic rejection of immunologic origin as well as glomerular capillary lesions. The negative MSPTC in the patients with chronic rejection suggest that the deterioration of the graft function is probably non-immunologic in origin.