In newborn children, essentially all bones have active marrow. In adults, active marrow is found mainly in the center of the pelvic bones, ribs, spine and collarbones. When an appropriate donor is identified, active marrow usually is removed from these bones with needles and a syringe. In some circumstances, it is possible to remove stem cells from blood.
Needle Aspiration Most bone marrow transplants involve extracting bone marrow from the bones of the pelvis by repeated needle punctures. The donor is usually under anesthetic during this process, which is a good thing, for it takes 150 or 200 needle punctures to remove enough marrow for a transplant—about 500 to 1,000 cc (one or two pints).
How the bone marrow is handled after it is removed depends upon the type of transplant to be done.
• If the transplant is allogeneic and the donor and the recipient have the same ABO red blood cell type, the
marrow is immediately given intravenously.
• If the red blood cells of the donor and recipient are incompatible, the red cells can be separated and discarded.
• If an autotransplant is planned, the cells have to be stored. This requires mixing them with a substance to
prevent ice from forming and then freezing the cells in liquid nitrogen. The cells are sometimes also treated with
chemicals or antibodies—in a process called marrow purging—to try to remove potentially contaminating
cancer cells. It is not yet known how effective this is.
