Bone marrow is a soft, fatty tissue inside the bones. This is where blood cells (red blood cells, platelets, and white blood cells) are produced, and develop.
In some diseases of the blood cells -- especially cancers such as leukemia -- high doses of chemotherapy may be needed to destroy the cancer. However, this also destroys normal bone marrow and prevents it from making enough blood cells.
In other cases in which hereditary or acquired disorders cause abnormal blood cell production, a transplant of healthy bone marrow may correct these problems. Transplanted bone marrow will restore production of white blood cells, red blood cells, and platelets.
Bone marrow transplant patients are usually treated in specialized centers. The patient stays in a bone marrow transplant unit, or BMT, to limit exposure to infections.
The healthy bone marrow may be taken from the patient before chemotherapy or radiation treatment (autograft). Or, it may be taken from a donor (allograft). The donor can be a relative (usually a brother or a sister), or an unrelated person (found through the national marrow donor program).
Donated bone marrow must match the patient's tissue type. Donors are matched through special blood tests called HLA tissue typing (see HLA antigens).
Bone marrow is taken from the donor in the operating room while the donor is unconscious and pain-free (under general anesthesia). Some of the donor's bone marrow is removed from the top of the hip bone. The bone marrow is filtered and treated. It can be transplanted immediately or frozen and stored for later use.
Transplant marrow is given to the patient through a vein (IV). It is naturally carried into the bone cavities, where it grows to replace the old bone marrow.
The patient is prepared for transplant by getting high doses of chemotherapy or radiation (conditioning). This serves two purposes:
It destroys the patient's abnormal blood cells or cancer.It slows the patient's immune response against the donor bone marrow (graft rejection).
Following conditioning, the patient is ready for bone marrow infusion. After infusion, it takes 10 - 20 days for the bone marrow to establish itself. During this time, the patient will need support with blood cell transfusions.
