G-CSF Mobilized Leukapheresis for Improved Stem Cell Selection in Transplantation

The NHLBI Stem Cell Transplantation program is exploring ways to make allogeneic transplantation safer and more widely applicable. Prior NHLBI transplant protocols have evaluated the strategy of using T cell depleted marrow transplants followed by delayed lymphocyte add-back to control or prevent GVHD while conserving useful donor immune function against residual leukemia and infectious agents. Over the past ten years, a number of increasingly efficient methods have been used to deplete T cells but retain stem cells, and we have shown the safety and utility of the delayed T cell add-back approach. We have also found a positive relationship between the administration of higher CD34+ cell doses and outcome. Investigation of highly purified grafts with the add-back of specific T cell populations is ongoing, and the ability to test new purification approaches and devices on clinical-scale PBSC products is critical to the continued development of new transplantation approaches in our program. This requires testing the approaches on G-CSF mobilized PBSCs collected by apheresis from healthy donors since this is the cell source that will be used in all clinical allogeneic transplantation protocols in our program. Therefore, the primary intent of this protocol is to provide a mechanism for mobilizing, collecting, storing, and analyzing G-CSF mobilized apheresis samples from healthy volunteers. Cells will be used to develop a method of processing the cells that are collected after stimulation with G-CSF, by removing the lymphocytes, which can mediate GVHD while retaining the stem cells which are necessary for hematopoietic reconstitution. At the same time, we will study whether G-CSF administration has an effect on lymphocyte, function which may influence the immune reactions occurring in allogeneic bone marrow transplantation. Furthermore, the CD34+ cells collected will be a valuable resource for experimental studies of lymphocyte-stem cell interactions in our laboratory.