Bone marrow, sponge-like tissue found in the center of certain bones, contains stem cells that are the precursors of white blood cells, red blood cells, and platelets. These blood cells are vital for normal body functions. Blood cells have a limited life span and are constantly being replaced; therefore, healthy stem cells are vital.

In association with certain diseases, stem cells may produce too many, too few, or otherwise abnormal blood cells. Also, medical treatments, particularly chemotherapy or radiation treatment, may destroy stem cells or alter blood cell production. The resultant blood cell abnormalities can be life threatening.

Bone marrow transplantation involves extracting bone marrow from a healthy donor and transferring it to a recipient whose body cannot manufacture proper quantities of normal blood cells. The goal of the transplant is to rebuild the recipient's blood cells and immune system and cure the underlying...