Differences in chronic intragraft inflammation between positive crossmatch and ABO-incompatible kidney transplantation

Background: ABO-incompatible kidney transplantations (ABOiKTxs) seem to have better long-term outcomes than positive crossmatch kidney transplantations (+XMKTxs). Methods: This study aimed to assess the differences in chronic injury on histologic findings on 1- and 5-year surveillance biopsies and the clinical outcomes in living-donor kidney transplantations performed between May 1999 and November 2006 including 102 +XMKTxs, 73 ABOiKTxs, and 652 conventional KTxs. Results: Although 5-year patient survival was similar between groups, graft loss between 1 and 5 years was similar in ABOiKTx (2.6% per year) and conventional KTx (1.7% per yr), and both were lower than that of +XMKTx (5.8% per year). At 5 years, renal function was similar in ABOiKTx and conventional KTx, and both were higher than that of + XMKTx, which had higher rates of inflammation and chronic glomerulopathy on both 1- and 5-year biopsies. Despite having evidence of less chronic injury, ABOiKTx showed a higher rate of intragraft complement activation (C4d deposition) at 5 years compared with +XMKTx (77.8% vs. 18.9%, P<0.001). Conclusion: These data suggest that +XMKTxs have high rates of chronic inflammation at 1 and 5 years after transplantation, which may explain the higher rates of graft loss and lower renal function compared with other factors such as anti-donor antibody or intragraft complement deposition.