The primary goal of the research program of the Hematologic Diseases Section is to develop new treatment strategies for hematologic malignancies, the most frequent cancer type in pediatrics. Although cure rates are excellent for many subtypes of childhood leukemia and lymphoma, new approaches are needed to overcome resistance to standard therapies and to decrease treatment-associated sequelae in survivors of pediatric cancer. The section conducts collaborative pre-clinical, translational, and clinical studies in pediatric hematologic malignancies. Major foci of investigation include the development of targeted agents and the application of immunotherapy to direct anti-tumor responses for childhood leukemias and lymphomas. Current activities include the following: Development of anti-CD22 immunotoxins and other targeted agents and immune-based therapies; Novel approaches to hematopoietic stem cell transplantation; Post-transplant allogeneic immunotherapy to direct anti-tumor responses; Investigations into the biology, prevention, and treatment of relapse after allogeneic stem cell transplantation; Investigations into the biology, prevention, and treatment of graft-vs-host disease; Pre-clinical studies designed to support current and future translational trials, to apply new methodologies in the study of cellular, molecular, genetic, and genomic biology, and to probe for new therapeutic targets.