MINI-SYMPOSIUM: PATHOLOGY OF TRANSPLANTATION

Summary The renal transplant biopsy plays a central role in the diagnosis of renal allograft dysfunction; in particular in differentiating immune-mediated rejection from various infective, ischaemic and toxic pathologies. Recent advances have been made in refining the histological criteria for rejection diagnosis. The Banff ’97 classification of renal allograft pathology has gained almost universal acceptance. In this classification, acute rejection is divided into three main types, tubulointerstitial, vascular and severe vascular, that differ in response to anti-rejection therapy and long-term prognosis. There remain, however, a number of challenges; interpretation of biopsies showing borderline changes, the diagnosis of humoral rejection and differentiating rejection from interstitial nephritis associated with viral infections present specific problems. There are potential applications for new molecular and immunohistochemical techniques in these areas. Other challenges arise from the application of the Banff classification. Recent validation studies have indicated that the reproducibility of some Banff criteria is low and that there are a number of histological features, not included in the Banff schema, that may be useful in rejection diagnosis. New roles for the transplant biopsy are developing in the management of patients with stable graft function, as indicated by measurement of serum creatinine. Protocol biopsies performed at regular intervals in the early post-transplant period may be used to predict subsequent development of chronic allograft nephropathy, the major cause of graft loss. The interpretation of these biopsies may be refined using morphometric techniques and immunohistochemistry for cytokines and matrix components. Protocol biopsies may also be used to diagnose sub-clinical rejection, and early evidence indicates that treatment of these histological rejections improves long-term graft outcome. The role of the transplant biopsy will continue to evolve with greater use of organs from marginal donors, improved understanding of the processes of graft injury and fibrosis, and the introduction of new immunosuppressive regimens. ^ 2000 Harcourt Publishers Ltd