The graft-versus-leukemia effects of allogeneic cell therapy.

Until recently, the only cure for relapse after allogeneic bone marrow transplantation (BMT) has been a second BMT. Recently, infusions of leukocytes collected from the original transplant donor have been used to induce a direct graft-versus-leukemia (GVL) reaction in patients with relapsed disease. Adoptive immunotherapy with donor leukocyte infusions (DLI) results in complete remission for 60-80% of patients with relapsed chronic-phase CML; therapy is also effective for relapse of diseases other than CML, although response rates are lower. Adoptive immunotherapy induces remissions for the majority of patients with post-transplantation Epstein-Barr virus-related lymphomas and other viral-associated illnesses. The extraordinary success of DLI demonstrates that it is now possible to harness the GVL potential of the human immune system for clinical benefit. The necessary effector cells and target antigens required for GVL reactivity are poorly defined but are the subject of intensive investigation. Future trials will investigate strategies that retain and enhance the GVL effects while limiting toxicity from this therapy, and they may define methods of successful allogeneic adoptive immunotherapy outside the setting of allogeneic BMT.