Mixed erythrocyte chimerism: implications for tolerance of the donor immune system to recipient non-ABO system red...

We report a case of a minor degree of ABO incompatibility in a BMT recipient, demonstrating mixed RBC chimerism, who, late in the post-transplant period, developed a warm autoimmune hemolytic anemia and subsequently developed antibodies with donor-anti-recipient specificities for non-ABO system RBC antigens. While this implies a lack of tolerance of the donor immune system for recipient non-ABO system RBC antigens, other factors may be operating and should be evaluated before such a conclusion is reached. Underscored is the importance of obtaining pretransplant RBC antigen phenotypes on both the recipient and donor.