Bone marrow contains the hematopoietic stem cells from which all the types of blood cells are made.
Most failures of autologous marrow transplants occur because of failure to get all the leukemic cells out of the harvested marrow rather than failure to eliminate them from the patient. This is marrow removed from someone else, usually a close relative. Allogeneic marrow avoids the problem of lurking residual cancer cells but Must be closely matched to the major histocompatibility loci of the patient.