Answer: Bone Marrow Transplant

Most of our defining characteristics are stable over time: our eye color doesn’t change, our finger prints are fixed, and for most people, characteristics like blood type stay the same over the course of their entire lives. That is, unless, they have a bone marrow transplant.

How can someone get a new blood type after a bone marrow transplant? It’s a unique situation that results from both how donors and recipients are matched as well as how red blood cells are produced. When a hospital is searching for a donor, they match the recipient and the donor based on their human leukocyte antigen (HLA) tissue because the antigens on the surface of these specialized white bloods cells need to match between the marrow donor and recipient. Blood type is irrelevant to the procedure.

Yet bone marrow produces our red blood cells, so if the donor and the recipient have compatible antigens but different blood types, the donor’s marrow (which replaces the recipient’s marrow) will begin producing the new blood cells, replacing all the old cells over the course of several weeks to months.