Therapeutic apheresis therapy for ABO-incompatible renal transplantations.

The most important transplantation antigen system for organ transplantation is the ABO blood group system. Crossing the blood barrier is usually not done except in emergency cases such as liver transplantations for fulminant hepatitis. Early experiences of allograft transplantations across the blood barriers were discouraging. In the 1970s, clinical trials were started transplanting kidneys of subgroup A2 into blood group O recipients because the tissues of the A2 subgroup express a lower amount of A antigens compared with subgroup A1. The recipients required no special treatment and received the standard immunosuppressive regimen as used in blood group identical cases. Many early graft loses immediately after transplantations were experienced, but these trials resulted in an excellent graft survival rate. A few centers have adapted the concept of A2 kidneys to non-A recipient transplantations with successful results by reducing anti-A blood type titers prior to transplantations. In the early 1980s, the possibility of bridging the ABO barrier was tested by several groups. A1 and B kidneys from living donors were also successfully transplanted across the blood barrier using quadruple immunosuppressive drugs and splenectomy. Since 1989, the largest number of ABO-incompatible renal transplantations have been performed in Japan because of the limited numbers of cadaveric donors. Approximately 400 cases have been successfully transplanted across the blood barrier at many centers in Japan. Owing to novel immunosuppressive drugs, the ABO-incompatible allografts exhibited a level of function comparable with that of ABO-matched allografts even though anti-A or anti-B antibodies had returned to the circulation of the recipients. In this article, we describe the historical background, the current therapeutic strategies including apheresis therapy for the ABO-incompatible transplantations, and the experiences at our institution.