A bone marrow transplant can be helpful in replacing damaged or destroyed bone marrow needed by the body for the production of blood cells. Bone marrow transplants are used to treat multiple disorders, such as lymphoma, leukemia, multiple myeloma, aplastic anemia, severe immune system disorders and sickle cell anemia, according to Medline Plus.
Identification
The centers of large bones are filled with a spongy material called bone marrow. Marrow contains immature cells called stem cells that produce red blood cells, platelets and white blood cells. Red cells transport oxygen throughout the body, platelets assist in blood clotting and white blood cells fight infection. When the marrow is compromised, normal production of these cells is affected. Marrow can also be damaged or destroyed after chemotherapy or radiation treatments to treat cancer. During a bone marrow transplant, damaged or missing bone marrow is replaced with donor marrow in an attempt to restart the normal blood cell production process.
Types
Transplants that use donor bone marrow are called allogenic bone marrow transplants. Donors must have the same tissue type as the patient. During an autologous bone marrow transplant, healthy stem cells are removed from the patient before chemotherapy or radiation treatments begin. After treatments end, the patient receives his own cells in a transplant. Stem cells can also be transplanted from umbilical cord blood. Blood is removed from the umbilical cord shortly after a baby is born and stored for future use.
Donor Matching
Both patient and donor must undergo blood tests to determine if tissue types match if the patient is not using her own stem cells. The test looks for a match in human leukocyte-associated (HLA) antigens. HLA antigens are a type of protein found on cell surfaces. Close relatives, such as brothers and sisters, are more likely to qualify as matches, but only 25 to 35 percent of patients have an HLA-matched sibling, according to the National Cancer Institute (NCI). If family members don't have matching HLA antigens, marrow from unrelated bone marrow donors can be used for the transplant.
Transplant Preparation
Stem cells are retrieved from the patient prior to cancer treatment if an autologous transplant is used. Special procedures may be needed to remove cancer from the cells prior to the transplant. If a donor is providing cells, the cells are harvested during a procedure in which a hollow needle is inserted into the donor's hip bone. The needle pierces the center of the bone and withdraws marrow. After the marrow is harvested, bone fragments and blood are removed during processing.
Transplant Procedure
Patients receive stem cells from an intravenous (IV) line placed in a vein. The transfer takes one to five hours, according to the NCI. Transplanted stem cells travel through the bloodstream to the bone marrow, where they begin making platelets and red and white blood cells. This process is called engraftment and takes place two to four weeks after the transplant. While the new marrow may be producing cells, immune system function may not completely recover until several months to several years following the transplant, depending on the type of the transplant.
