Stem cells are produced in the spongy area of bones known as marrow. These cells develop into all types of blood cells in the body. A stem cell/bone marrow transplant replaces damaged or destroyed bone marrow stem cells with healthy ones.
The types of hematopoietic (blood) stem cell transplants are:
Allogeneic: in which hematopoietic stem cells from one person are transplanted into another. The donor and recipient can be related or unrelated. These persons include HLA-matched siblings, mismatched family members or unrelated donors.
Autologous: in which a person receives stem cells that he or she donated earlier.
Syngeneic: in which the patient and donor are identical twins.