Donor leukocyte infusions after unrelated donor hematopoietic stem cell transplantation.

Purpose of Review: Donor leukocyte infusions provide direct and potent graft-versus-tumor activity to treat relapse after allogeneic stem cell transplantation. Extensive data are available on the use of donor leukocyte infusion after matched-sibling stem cell transplantation, but reports are remarkably few on the use of donor leukocyte infusion after unrelated-donor stem cell transplantation. But the role for unrelated-donor leukocyte infusion is not well established.
Recent Findings: The dramatic success of donor leukocyte infusion to treat relapse after matched-sibling stem cell transplantation has led to the use of unrelated-donor leukocyte infusion in many patients. Several case studies suggest that unrelated-donor leukocyte infusion effectively induces direct graft-versus-tumor reactions with toxicity comparable to that of matched-sibling donor leukocyte infusion. Important issues include the relationship between dose and response/toxicity appropriate timing, dose, and schedule; and identification of the best tumor targets. In particular nonmyeloablative transplant strategies using unrelated donors are expanding rapidly, but relapse rates are high. There is a paucity of data on unrelated-donor leukocyte infusion in this setting.
Summary: This review summarizes recent data on the use of unrelated-donor leukocyte infusion. We discuss anticipated outcomes and identify areas under active investigation in both ablative and nonmyeloablative unrelated-donor stem cell transplantation.