Acute renal allograft rejections with major interstitial oedema and plasma cell-rich infiltrates: high gamma-interferon expression and poor clinical outcome.

Background: Acute rejections are scored according to three main criteria: vasculitis, tubulitis and interstitial infiltration as defined in the Banff classification. Typically, B cells account for <8% of the infiltrates and oedema is limited. The clinical significance of severe interstitial oedema and plasma cell-rich infiltrates (OPcR) are still a matter of debate.

Methods: Kidney graft biopsies performed between 1991 and 1998 were retrospectively evaluated for these two criteria.

Results: Among the 826 biopsies performed during the study period, 14 samples in 12 patients met these criteria; 11 were of Banff type I acute rejection and three were borderline. Based on clinical data, all were treated as acute rejections. OPcR occurred at a median of 187 days post-transplantation. All episodes were steroid resistant. Graft survival was 40% at 1 year following the rejection. Circulating antibodies reactive either to donor HLA or to endothelial cells were present in eight of 12 patients and widespread C4d deposit in peritubular capillary were present in three out of five patients studied. Level of gamma-interferon mRNA within the graft was significantly higher than in standard acute cellular rejection (ACR).

Conclusion: This study showed that OPcR rejections portend a poor outcome irrespective of the Banff score. Our data strongly support the hypothesis that a humoral component participated in the graft injuries. Altogether, the data suggest that OPcR rejection might represent a late and attenuated variant of acute humoral rejection that should be classified separately from ACR.