Histologic findings of antibody-mediated rejection in ABO blood-group-incompatible living-donor kidney transplantation

The purpose of this study was to characterize the histology of antibody- mediated rejection (AMR) in ABO blood- group- incompatible (ABOI) kidney transplants as well as on protocol biopsies performed at the time of stable allograft function. Between 5/ 99 and 1/ 02, we performed 32 ABOI kidney transplants (13 A2, 19 non- A2 blood- group living donors). Nineteen biopsies were performed for allograft dysfunction, and 127 protocol biopsies were performed 0, 3, 7, 14, 28 days and 3 and 12 months post transplant. Twenty- five of 32 patients have functioning allografts (mean 585 days post transplant). Nine of 32 (28%) developed clinical AMR. Biopsy revealed glomerular thrombi (78%), mesangiolysis (78%), peritubular capillary C4d staining (56%) and neutrophil infiltration (67%), interstitial hemorrhage and necrosis (56%) and arteriolar thrombi (33%). Subclinical AMR was diagnosed by protocol biopsies in four patients. Findings consisted of glomerular thrombi (100%), mesangiolysis (25%), and C4d staining (100%). In late protocol biopsies performed 214420 days post transplant, mild mesangiolysis was seen in 2/ 17 (11.7%), and C4d immunostaining was detected in 3/ 12 (25%). AMR is characterized by glomerular thrombi, mesangiolysis, peritubular capillary neutrophil infiltration interstitial hemorrhage, necrosis, and C4d deposition. Glomerular thrombi appear early in AMR and may appear prior to graft dysfunction.