Bidirectional graft-host hematological traffic in liver transplantation

Immune hemolysis following transplantation of a blood group O liver into a non-O recipient has been seen since the early days of transplantation when it was reported by Ramsey et al. (1). It is thought to be due to the production of antibodies by the donor-derived B lymphocytes in an immune response against the recipient’s red blood cell (RBC) antigens (1). This graft-versus-host (GVH) phenomenon has been called the passenger lymphocyte syndrome (PLS) because the donor B lymphocytes have taken passage with the organ into the recipient. The organ donor-recipient match, described above, used to be called a compatible mismatch but is now classified as minor incompatibility, borrowing terminology from stem-cell transplantation. If the combination of donor and recipient was reversed, accelerated or hyperacute rejection could occur and the match is classified a major incompatibly (2,3). Bidirectional incompatibility may occur if a group A liver is transplanted into a B recipient, or the reverse. In North America, allocation of blood group A2 grafts to blood group B recipients is being considered as a way to provide more equitable access to transplantation in which case the match might be considered to have bidirectional minor incompatibility