Patients who have received a blood and marrow transplant (BMT) from a related or unrelated donor could still experience a relapse of their underlying disease/cancer. A donor leukocyte infusion (DLI) is a possible strategy for managing a patient in relapse. In this procedure, the patient receives a boost of immune cells from the original donor's blood. In certain circumstances, it may be extremely effective in controlling recurrent cancer in a patient.
It has been found that T-cells, a type of leukocyte from the donor not only can cause graft-versus-host disease (GVHD), but can also initiate an attack on the malignant cells that remain after high-dose chemo/radiotherapy. This ability of the donor cells to control or eliminate the residual malignant cells has been called the graft-versus-tumour effect.
Most patients who respond to DLI also develop graft-versus-host disease (GVHD) and/or experience a marked drop in their blood counts, as the bone marrow switches back to donor cells once again. The severity of the GVHD has generally been mild to moderate, and controllable with medications. It has however proved fatal in 5-10% of patients of cases where patients developed complications or infections stemming from the GVHD following DLI.
DLI treatment has mostly been used for relapsed Chronic Myeloid Leukemia (CML), where it has been extremely effective. It has also been used for other leukemias and lymphoproliferative disorders.