Peripheral Blood Stem Cells: A Novel Source for Allogeneic Transplantation

Cytokine-mobilized peripheral blood stem cells (PBSCs) are increasingly viewed as a promising alternative to bone marrow (BM)-derived stem cells for allografting in patients with hematologic malignancies. Preliminary results seem to indicate several potential advantages of this approach, such as: A) a more "donor-friendly" and possibly safer stem cell collection procedure; B) the procurement of a significantly larger number of progenitor cells (allowing for graft engineering opportunities); C) a faster hematopoietic engraftment including immunologic reconstitution, and D) comparable rates of acute graft-versus-host disease. Although the superiority of this approach over the traditional BM allografting has not been clearly demonstrated thus far in a randomized trial and many open issues remain, experience is accumulating rapidly, and major transplant centers worldwide seem to have endorsed this procedure. The acceptance of the peripheral blood as the primary source of stem cells for hematopoietic reconstitution in the allogeneic setting is likely to have a profound impact in areas such as graft-versus-leukemia/tumor effect, unrelated donor registries, and transplants. In the following, currently available information on blood stem cell harvesting and allografting is reviewed with the particular focus on donor safety.