The influence of HLA mismatches and immunosuppression on kidney graft survival: an analysis of more than 1300 patients

New immunosuppressive drugs used in kidney transplantation decreased the incidence of acute rejection. It was hypothesized that, with their power, the importance of HLA matching was decreased. To evaluate the influence of HLA matching, immunosuppression, and other possible risk factors, we analyzed data of 1314 consecutive deceased donor kidney transplantation. We divided the patient population into 4 cohorts, according to the era of transplantation: era 1, before 1990, azathioprine (Aza) and cyclosporine (Csa) no microemulsion; era 2, between 1990 and 1995, Csa microemulsion; era 3, between 1996 and 2000, wide use of mycophenolate mofetil (MMF) and anti-thymocyte globulin (ATG); and era 4, after 2000, marked by sirolimus and tacrolimus (TAC) use. Multivariate analysis compared death-censored graft survival. Using as reference the results obtained with 0 HLA mismatches, we verified, during era 1 and era 2, an increased risk of graft loss for all of the subgroups with HLA mismatch >0. However, during era 3 and era 4, the number of HLA mismatches did not influence graft survival. Although acute rejection and delayed graft function, which decreased in the later periods, remained as prognostic factors for graft loss. Considering the immunosuppressive protocol with Csa+Aza+Pred as reference, protocols used after 1995 with Pred+Csa+ATG, with Pred+Csa+MMF, and with Pred+Tac+MMF presented better survival results. Results showed that the significance of HLA matching decreased while the results improved with the new immunosuppressant drugs. These observations support the hypothesis that the weakened importance of HLA matching may be a consequence of the increasing efficacy of the immunosuppression.