NIV Congres

Background Blood type O patients are at a disadvantage for matching with a compatible blood type kidney donor in donor exchange programs compared to blood type A or B patients. In recent years protocols have been developed that allow for transplantation of ABO blood type incompatible (ABOi) kidneys without the need for splenectomy. These less invasive protocols aim to desensitize the patient pre-transplantation and have greatly improved graft survival. This study describes the Rotterdam experience with ABOi kidney transplantation.

Methods Four weeks pretransplantation patients received a single dose rituximab and started triple immune suppression (tacrolimus, mycophenolate mofetil, prednisolon) two weeks later. Immunoadsorption (IA) using columns with either synthetic A or B epitopes was performed in the week before transplantation. The frequency of IA depended on the height of the anti donor blood type antibody titers at the start of the protocol and the objective was to lower the titer to <1:8 the day before transplantation.  Fifty  patients received a ABOi kidney transplant in a period from 2006 to 2012. We matched 100 ABO compatible controls for age of donor and recipient during the same period.

Results In the ABOi group a very high percentage (86%) of the patients had bloodtype O, compared to only 39% in the control group. The donors had bloodtype O in 60% of the controls. Within the first week, 11 antibody mediated humoral rejections were noted of which 3 were mixed humoral and cellular mediated rejection. Inaddition 9 cellulair mediated rejection occurred, mostly within the first week after transplantation. AMR was treated with prednisolon and IVIG, and when not effective followed by ATG. During the first year two grafts were lost due to rejection. One year graft survival and renal allograft function of the ABOi grafts were similar to 100 matched ABO compatible renal grafts, 96 % vs 99%. At 5 year follow up graft survival was 90% in the ABOi  vs 97% in the control group. Adverse infectious events specifically related to the ABOi protocol were not observed.

Conclusion The currently used ABOi protocol shows good short and long-term results despite a relatively high frequency of humoral rejection.The program facilitates an optimal use of the available living kidney donors and the bloodtype O patient benefits especially from this program.