The doctors in the Bone Marrow Transplant Service at the Indiana University Cancer Center are working to better understand how the immune cells that cause graft-versus-host disease (a major complication of stem cell transplantation in which the donor immune cells attack the patient's organs) can be selectively removed from the graft, leaving other immune cells that fight infections.

The purpose of this research is to study how immune cells (called T cells) that cause graft-versus-host disease (GVHD) can best be selectively separated from other T cells and removed from the cells that will be returned to the cancer patient's body. These other T cells may protect against infection when given to patients after a stem cell transplant. The removal of cells that cause GVHD would allow doctors to safely give back the T cells that protect against infection, without the risk of GVHD.

Inclusion Criteria:

• Patients with hematological malignancies who are undergoing evaluation for autologous or allogeneic stem cell transplants will be eligible, if: (1)They have no circulating neoplastic cells in the peripheral blood as assessed by routine morphology or flow cytometry. (2)Patients with acute myeloid or lymphocytic leukemia are in complete remission
• First-degree relatives of patients evaluated for stem cell transplantation will be eligible if: (1) Willing to undergo testing for HIV and hepatitis B and C (free of charge) (2) Not pregnant at time of collection of blood (3)In good general health (4) No prior history of malignancy. (5) Age 18 years or older if donating apheresis product. (Because of the relatively invasive nature of the leukopheresis procedure and difficulties in obtaining consent, children <18 who are first degree relatives of the patient will not undergo apheresis for studies on this protocol)
• Written informed consent

Exclusion Criteria:

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Patients from the Bone Marrow Transplant service at the Indiana University Melvin and Bren Simon Cancer Center.