A clinical role for peripheral blood lymphocyte infusions and perspectives on collection

Molecular remissions were observed in some relapsed post allogeneic transplant chronic myeloid leukemia (CML) patients who received donor peripheral blood lymphocyte infusions (DLI). This was indirect evidence of immune-mediated tumor cell killing, and the process was termed graft-versus-leukemia (GVL). Mechanisms were hypothesized to be direct T cell mediated cell lysis or augmented programmed cell death. These observations formed the basis for exploring the role of DLI first in relapsed allogeneic transplant patients with other hematologic malignancies, then as prophylaxis for patients at high risk for relapse and then as adjunctive therapy for transplant strategies utilizing non-myeloablative conditioning regimens. Multiple clinical trials are underway to define dose, schedule, clinical and molecular response and laboratory assays to distinguish lymphocyte subsets mediating GVL and those responsible for graft-versus-host disease (GVHD) toxicity. This review outlines some of the donor/patient and therapy variables involved and some principles of mononuclear cell collection for cellular immunotherapy.