Stem cell transplantation requires careful regulation of immune cell function to allow the donated stem cells to grow in the transplant recipient, to prevent the transplanted cells from damaging the recipient, and to allow the recipient's new immune system to develop normally so it can fight infections. Studies comparing the outcome of patients transplanted with bone marrow cells with those transplanted with stem cells suggest that the G-CSF given to stem cell donors affects the function of T cells in transplant recipients. This study will collect white cells containing T cells before and after G-CSF administration to determine the effects of the drug on both T cells and stem cells.