CD-34 Selection for Ex-vivo T-Cell Depletion of Mobilized Peripheral Blood Stem Cells for Recipients of HLA Haploidentical Related Donor Stem Cell Grafts Receiving Intensive Conditioning

Subjects are being asked to participate in this study because treatment of their disease requires them to receive a stem cell transplant. Stem cells or "mother" cells are the source of normal blood cells and lead to recovery of blood counts after bone marrow transplantation (BMT). Unfortunately, there is not a perfectly matched stem cell donor (like a sister or brother) and the subject's disease is considered rapidly progressive and does not permit enough time to identify another donor (like someone from a registry list that is not their relative). We have, however, identified a close relative of the subject's whose stem cells are not a perfect match, but can be used. However, with this type of donor, there is typically an increased risk of developing graft-versus-host disease (GVHD), a high rate of transplant failure, and a longer delay in the recovery of the immune system.

GVHD is a serious and sometimes fatal side effect of stem cell transplant. GVHD occurs when the new donor cells (graft) recognizes that the body tissues of the patient (host) are different from those of the donor. When this happens, cells in the graft may attack the host organs, primarily the skin, liver, and intestines. The number of occurrences and harshness of severe GVHD depends on several factors, including the degree of genetic differences between the donor and recipient, the intensity of the pre-treatment conditioning regimen, the quantity of transplanted cells, and the recipient's age. In recipients of mismatched family member or matched unrelated donor stem cell transplants, there is a greater risk of GVHD so that 70-90% of recipients of unchanged marrow will develop severe GVHD which could include symptoms such as marked diarrhea, liver failure, or even death.

In an effort to lower the occurrences and severity of graft-versus-host disease in patients and to lower the rate of transplant failure, we would like to specially treat the donor's blood cells to remove cells that are most likely to attack the patient's tissues. This will occur in combination with intense conditioning treatment that the patient will receive before the transplant.