Which of the following is true regarding bone marrow transplantation?

Bone marrow cells are highly immunogenic. Successful engraftment requires the use of powerful immunosuppressants that permit the transplanted cells not only to survive the host's immune response, but also to mount a graft-versus-host response against recipient tissues. The graft-versus-host response is the major impediment to more widespread clinical use of this technique. Despite these barriers, human bone marrow transplantation has had important clinical application in the treatment of aplastic anemias and congenital immunodeficiency diseases and several hematologic malignancies. Stem cell transplantation involves harvesting of a patient's own pluripotent bone marrow cells and subsequent reestablishment of the marrow following high-dose, toxic chemotherapy for advanced cancer. This modality has been used in the treatment of recurrent breast cancer, but recent metanalyses of the results have failed to show any significant survival benefit. In experimental models, work with bone marrow transplantation for the induction of tolerance to organ allografts has proved highly promising. This may provide a key for the development of treatment protocols in organ transplant recipients that would avoid or reduce the need for toxic systemic immunosuppressants.