Laboratory approaches in desensitization for ABO-incompatible transplantation.

ABO-incompatible transplantation, once considered contraindicated due to the risk of hyperacute rejection, has become a viable option owing to advances in immunosuppression and desensitization methods. Accurate measurement and effective reduction of anti-ABO isoagglutinin titers are essential for the success of ABO-incompatible transplantation. This review summarizes the principles of hemagglutination and the measurement of isoagglutinin titers, highlighting variables that influence agglutination sensitivity. The clinical significance of isoagglutinin rebound and its association with rejection risk are also discussed, along with ongoing efforts toward laboratory standardization. Antibody-mediated rejection (AMR) is strongly linked to high pretransplant isoagglutinin titers (≥1:32). Posttransplant isoagglutinin rebound-an important risk factor for AMR-requires careful monitoring in liver and kidney transplant recipients with high initial titers. Desensitization strategies include rituximab, plasmapheresis, intravenous immunoglobulin, bortezomib, and emerging agents such as tocilizumab and imlifidase. This review aims to enhance understanding of the immunological and laboratory aspects of ABO-incompatible transplantation.