• antidonor HLA antibody;
  • C4d;
  • chronic humoral rejection;
  • chronic rejection;
  • multilayering of PTC basement membrane (MLPTC);
  • peritubular capillary (PTC)

Abstract:  The association of humoral immunity with late renal allograft dysfunction has recently been recognized, and many reports have revealed C4d deposits in peritubular capillaries (C4d in PTC), and the presence of serum antidonor HLA antibody in patients suffering from graft dysfunction, long time after transplantation. In this study, morphological changes in renal allograft biopsies more than 1 year after transplantation in 14 patients with C4d in PTC and serum antidonor antibody were investigated for the presence of chronic rejection (CR). In addition to the light microscope study, an electron microscope study was done to evaluate the multilayering of the peritubular capillary basement membrane (MLPTC). Histologically, only seven of 14 patients met the criteria of CR, and 71.4% (5/7) of CR patients had episodes of acute humoral rejection (AHR), coexisting with acute tubulointerstitial rejection. Peritubular capillaritis was observed in all patients, although it differed in severity. Transplant glomerulitis and interstitial inflammation were also observed in many patients: 71.4% (10/14) and 92.9% (13/14) respectively. MLPTC was observed in 12 patients (85.7%), but the severity of the MLPTC did not reflect the severity of peritubular capillaritis or any other histological features. The long-term outcomes of the patients CR, especially those with episodes of AHR, were poor, and two of them lost their graft functions. On the other hand, patients without CR had relatively favourable outcomes. In conclusion, we confirmed the diverse morphological changes of late renal allografts, which cannot be categorized as chronic humoral rejection (CHR), and such patients who do not have typical morphological changes such as CHR, should be followed-up on a long-term basis in order to clarify the significance of C4d on PTC in late renal allografts.