Acute renal allograft rejection with intimal arteritis: Histologic predictors of response to therapy and graft survival

Background. Acute renal allograft rejection with intimal arteritis is designated by the widely used Banff 97 classification as type 2A or 2B depending on the extent of arteritis, without regard to interstitial inflammation or tubulitis. We examined whether the distinction between type 2A and 2B is relevant to short- and long-term clinical outcomes, and if outcomes in this subset of acute rejection also are affected by tubulitis, interstitial inflammation, and several additional histologic and clinical parameters. Methods. Pathology records were searched to identify cases of acute renal allograft rejection with intimal arteritis diagnosed between January 1985 and September 2000. For each case, the patient's chart was reviewed to determine the response of the rejection episode to therapy, type(s) of therapy given, and length of graft survival. All biopsies were reviewed and Banff acute and chronic indices recorded by a pathologist blinded to these data. Biopsies not showing type 2A or 2B rejection were excluded, as were repeat biopsies from the same patient and cases with recurrent glomerular disease, viral infection, donor-specific antibodies, or more than mild chronic change. Results. The initial response to anti-rejection therapy was significantly worse in patients with type 2B acute rejection (N = 29) than in those with type 2A (N = 102) by univariate and multivariate analyses, despite more aggressive treatment of type 2B rejection. In a Cox proportional hazards model the hazard ratio for graft failure for 2B versus 2A was 1.9 (P = 0.05), but this was not significant when adjusted for the initial response to therapy. Cases with minimal or mild tubulitis responded better to therapy than those with moderate or severe tubulitis, although graft survival was not significantly affected by the tubulitis score. Conclusions. The distinction between types 2A and 2B acute rejection in the Banff 97 classification has significant prognostic value with regard to both short- and long-term clinical outcomes, although the difference in long-term graft survival is mainly related to the initial response to therapy. Reports of biopsies showing type 2A or 2B rejection also should specify the degree of tubulitis present, as the latter may significantly influence the initial response to therapy.