bone marrow transplantation
Meaning of bone marrow transplantation: Less a transplant than an infusion, and with a donor graft the immune attack the new cells mount is part of the point.
Definition of bone marrow transplantation
Bone marrow transplantation is the delivery of blood-forming stem cells into the bloodstream to rebuild a marrow that has been destroyed, has failed, or is diseased. The cells travel to the marrow spaces on their own and begin producing blood there. Grafts may come from the person being treated, from a matched donor, or from an identical twin, and the cells are now often collected from blood rather than marrow.
Why is the name out of date?
Because most grafts no longer come from marrow. A course of a growth factor drug pushes stem cells out of the bone marrow into the circulating blood, where a machine can filter them out and return everything else, sparing the donor an operation. Banked umbilical cord blood supplies a third source. Nothing is implanted surgically at any point: the collected cells are dripped in through a vein like a transfusion and find the marrow cavities by themselves. The umbrella term now used is hematopoietic stem cell transplantation, which covers all three sources.
How do the types differ?
| Type | Where the cells come from | Defining feature |
|---|---|---|
| Autologous | The person's own cells, collected earlier | Permits very intensive treatment; no immune clash |
| Allogeneic | A matched donor, related or not | Donor immune cells act against residual disease |
| Syngeneic | An identical twin | A perfect match, but no immune effect on disease |
| Cord blood | Banked umbilical cord blood | Tolerates a looser match; fewer cells per unit |
What does a donor graft add?
Describing the procedure only as replacing marrow that treatment has destroyed fits the first row of that table and misses what a donor graft is for. Transferred immune cells recognize surviving leukemia cells as foreign and destroy them, and that reaction supplies much of the cure rather than being a side issue. Its mirror image is the central complication: the same donor cells may turn on the recipient's skin, gut and liver. Matching is done on tissue types inherited as a set, not on blood groups, which is why a sibling is the first place a match is sought. The procedure is also used for conditions that are not cancers at all, among them marrow failure, inherited immune deficiency, thalassemia and sickle cell disease, where a healthy donor marrow replaces a defective one.
Also known as
Used in a sentence
Bone marrow transplantation was considered once remission had been achieved.
Good to know
Most grafts are now collected from circulating blood or cord blood rather than from marrow, and in donor transplants the reaction of the graft against surviving disease is part of the intended effect, with graft-versus-host disease its mirror image.
Word origin
Where “bone marrow transplantation” comes from
Transplantation joins the Latin trans, meaning across, with plantare, to plant, so the word describes moving something and setting it down elsewhere.