ABO-Incompatible Kidney Transplantation with and without Splenectomy

Abstract

The letter to the editor from Dr. Mitsuhata et al. raises interesting points with regard to the role of splenectomy in ABO-incompatible (ABOI) kidney transplants. The authors contend that the classification of ABOI kidney transplant recipients as “high risk” should not be made on the basis of baseline antibody titer. The association of humoral rejection with baseline antidonor blood group antibody titer in splenectomized ABOI recipients not undergoing posttransplant plasmapheresis has been reported by Shimmura et al., who found a 70% humoral rejection rate in patients with baseline titer ≥128 and 20% in those with titers ≤1:64 (1). These findings are similar to those of our report in which rejection occurred in 12% of patients with titers <1:64, while 83% of those with titers exceeding 1:64 rejected (2). Interestingly, Shimmura et al. have recently reported that posttransplant plasmapheresis to maintain a low titer in conjunction with splenectomy is effective in preventing humoral rejection in ABOI recipients with very high baseline titers (3). In their letter, Mitsuhata et al. refer to their Brief Communication describing their use of mycophenolate mofetil during four weeks preceding ABOI transplantation in 18 patients compared to 18 patients who did not receive pretransplant mycophenolate mofetil (4). In their report, all patients underwent antibody lowering therapy with plasmapheresis or plasma exchange. No comment was made as to whether or not recipients underwent splenectomy, although their current letter to the editor implies that they did. They report improved allograft survival six months after transplant in the pretreated group, although the humoral rejection rate was comparable. The causes for allograft loss in the pretreatment group were not reported, nor were baseline antidonor blood group antibody titers. The authors indicate that on the day of transplantation antidonor blood group antibody titers ranging from 1–128, although not specifically reported. Given our admittedly smaller experience in ABOI kidney transplantation, we would be very reluctant to proceed to transplantation at the time the recipient's titer exceeded 1:16, and our practice is to continue to perform plasmapheresis until achieving a titer ≤1:8 on the day of transplantation. An important point is that the antibody titer depends strongly on the method used to measure it. It is possible that the antibody measurement technique used by Mitsuhata et al. differs from the technique reported in our investigation. The authors present their opinion that the benefits of transplantation without splenectomy are outweighed by the psychological, physical, and economic burden posed by posttransplant plasmapheresis and/or anti-CD20 antibody therapy. Our opinion is that with aggressive posttransplant antibody monitoring and therapy to maintain low titer during the first two weeks after transplantation, humoral rejection is an unusual complication in the large majority of ABOI kidney transplants. We also feel that the life long advantage of avoiding splenectomy exceeds the disadvantage of posttransplant therapy during the first one to two weeks after transplantation. Finally, the authors refer to the important fact that other potentially injurious antibodies with donor reactivity may also complicate ABOI transplantation, similar to ABO compatible transplants, and we agree. James Gloor Department of Internal Medicine and Nephrology Mayo Clinic Rochester, MN Mark Stegall Division of Transplantation Surgery Mayo Clinic Rochester, MN