Hematopoietic cell transplantation as a form of immunotherapy.

The association of graft-versus-host disease with diminished relapse rates following allogeneic hematopoietic cell transplantation, together with the dramatic responses sometimes seen following donor lymphocyte infusions, demonstrates the considerable power of the human immune system to eradicate hematological malignancies. The development of methods that reliably achieve complete engraftment of donor lymphohematopoiesis without subjecting patients to very-high-dose toxic chemoradiotherapy represents an important step in capitalizing on the allogeneic graft-versus-tumor effect. Nonmyeloablative hematopoietic cell transplantation can achieve complete chimerism in essentially all patients with HLA-matched siblings and the large majority of patients with matched unrelated donors. It can be carried out with relative safety, even in patients aged up to 70 years. Enduring complete responses have been seen in patients with virtually all varieties of hematological malignancies. Current studies are defining the role of this procedure in patient management. The greater challenge is to further capitalize on this approach by segregating the graft-versus-tumor effect from graft-versus-host disease.