Ex Vivo T-Cell Depletion of Mobilized Peripheral Blood Stem Cells Via CD34-Selection

Participants are being asked to take part in this study because treatment of his or her disease requires 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. Unfortunately, there is not a perfectly matched stem cell donor (like a sister or brother) for the participant and his or her disease does not permit enough time to identify another donor (like someone from a registry list that is not his or her relative) or another suitable donor has not been identified. However, a close relative of the patient has been identified whose stem cells are not a perfect match, but can be used. Alternatively, the patient may have already received a stem cell transplant but have evidence of mixed chimerism, which means some of the patient's own bone marrow cells are present, rather than all of the donor's cells. This may lead to an increased risk of the disease coming back. Or, the patient may have all donor cells but his or her bone marrow is not working very well, which may lead to frequent blood or platelet (cells that help in clotting blood) transfusions or infection. Regardless of the reason, it may be necessary to isolate stem cells from a haploidentical (half-match) donor in order to provide bone marrow function. Because the stem cells from the donor are only half-matched to the participant, the risk of graft-versus-host disease (GvHD) is very high. GvHD is a complication after transplant caused by donor T cells (graft) that attack the transplant recipient, and this complication can cause death after transplant. Thus, it is important that the donor's blood cells are treated to minimize cells that are most likely to attack the host's tissues. This is done by using a special device to capture the CD34+ stem cells from the donor's stem cell product prior to giving the cells to the host. This method minimizes the donor T cells, which are responsible for causing GvHD. Purpose: In an effort to lower the occurrences and severity of graft-versus-host disease in patients and to lower the rate of transplant failure, investigators would like to specially treat the donor's blood cells to minimize the cells that are most likely to attack the patient's tissues.