New rules of ABO-compatibility in kidney transplantation

ABO compatibility rules in kidney transplantation have been deeply modified with the possibility of ABO-incompatible transplantation. The recipient has to be prepared in the days preceding surgery with an objective of ABO antibody titers of 1/8 or less. This is obtained through a procedure including antibody removal, rituximab and IV immunoglobulins alone or in association according to the initial titer. All ABO combinations are possible. Due to the preparation of the recipient, living related transplantation has been first carried out but ABO-incompatible transplantation from a deceased donor is becoming common practice in some countries (A2 or A2B donor to a B recipient). Lower uncensored graft survival has been reported by some studies but not when ABO-incompatible kidney transplantations were compared with matched ABO-compatible ones. The infectious risk in the perioperative period, consequence of higher immunosuppression, raises concern. The interlaboratory variability in hemagglutination anti-A/B assays remains an important question among cohort studies which leads to development of new tests. ABO-incompatible transplantation is associated with a rare process, accommodation, that is well known in xenotransplantation and according to which, the transplant is protected against the consequences of ABO antibody binding. In human kidney ABO-incompatible transplantation, few studies are available but suggest that this protection against the post-transplant antibody rebound might be mediated by the expression of anti-complement molecules by endothelial cells.