Usefulness of Follow-Up Biopsies at One Year after ABO-incompatible Kidney Transplantation.

Background. Due to the shortage of deceased donor kidneys, we have expanded the indications for living-donor kidney transplantation (LKT) including ABO-incompatible (ABO-i) donor in Japan. In this study, the utility of protocol biopsies was discussed in ABO-i LKT.Methods. Protocol biopsies have been performed on kidney graft 1 hour, 3 weeks, and 1 year after LKT in our institution. The relationship between biopsies and clinical courses was considered retrospectively in 38 cases of ABO-i LKT. The immunosuppressive regimen consisted of anti-CD20 antibody, mycophenolate mofetil, prednisolone, calcineurin inhibitor (cyclosporine or tacrolimus), and anti-CD25 antibody. Anti-ABO blood type antibody removal by plasmapheresis was performed before LKT up to 32 times. The post-transplantation regimen consisted of mycophenolate mofetil or mizoribine as an antimetabolite.Results. Episode biopsies have been performed in 6 cases within 3 weeks post-transplantation. Each pathological diagnosis was as follows: antibody-mediated rejection (AMR; 5 cases) and calcineurin inhibitor (CM) nephrotoxicity (1 case). Subclinical chronic active AMR was found at 1 year post-transplantation follow-up biopsies in 4 of the 6 cases. Episode biopsies have been done in the other 6 cases from 1 month to 1 year post-transplantation. Each pathological diagnosis was as follows: acute T-cell mediated rejection (TMR; 1 case), vesicoureteral reflux (VUR; 3 cases), CNI nephrotoxicity (2 cases), and VUR + CNI nephrotmdcity (1 case). AMR was also not found at 1 year post-transplantation follow-up biopsies in them. In all cases episode biopsies were performed based on pathological diagnosis and had no graft dysfunction after that.Conclusions. Pathological study revealed that acute AMR was found early (ie, within 3 weeks) following transplantation. Although appropriate treatment made AMR go into remission once, chronic active AMR was often found at 1-year follow-up biopsies.