CLINICO-PATHOLOGICAL CHARACTERISTICS OF RENAL TRANSPLANTS AFTER ABO-INCOMPATIBLE KIDNEY TRANSPLANTATION

Abstract

O77 Aims: Both anti-HLA antibody and anti-blood group antibody are responsible for antibody-mediated humoral rejection. Clinicopathological characteristics of acute humoral rejection after ABO-compatible renal transplantation are well investigated, recently. However, those of ABO-incompatible renal transplantation are still unclear; especially in terms of correlation with concomitant ordinary (T-lymphocyte dependent) rejection and graft dysfunction. The precise pathogenesis occurred in acute rejection after ABO-incompatible renal transplantation is important. Methods: We studied the significance of C4d deposition in peritubular capillaries (PTC) as a sensitive indicator of humoral rejection and concomitant cellular rejection in renal allograft biopsies of ABO-incompatible renal transplantation. We analyzed 63 graft biopsy specimens from 27 patients with ABO-incompatible living recipients within 90 days after renal transplantation. Only diffuse and bright stain of C4d was consider as a positive finding of acute humoral rejection and severity of acute cellular rejection was classified by Banff scheme. Results: No graft was lost by acute rejection. Acute humoral rejection was noted in 14 graft biopsies; pure type in 8 and 6 combined with cellular rejection. Positive C4d was noted in all 14 graft biopsies. Ordinary cellular rejection was diagnosed in 14 biopsies. The diffuse C4d deposition in PTC was noted in 4 of 16 biopsies with acute tubulo-interstitial rejection of Grade I and no morphological findings of humoral rejection. Furthermore in the well functioning grafts with no morphologic findings of both humoral and cellular rejection, we found 3 diffuse and 2 focal and bright C4d positive biopsies. Focal and weak positive C4d is often noted in grafts without episode of graft dysfunction. No positive C4d deposition was noted in one-hour biopsy during transplant operation. Conclusions: Strong C4d deposition in PTC is valuable as a relatively specific and sensitive indicator for acute humoral rejection. However, the meaning of positive C4d is still unclear and requires further study after ABO-incompatible renal transplantation.