Participants will undergo a process called 'stem cell mobilization and apheresis' to collect bone marrow stem cells. For five days before the collection they will receive injections of a hormone called G-CSF, which stimulates release of stem cells from the bone marrow into the bloodstream. On the fifth day of the injections, stem cells will be collected through apheresis. For this procedure, blood is collected through a catheter (plastic tube) placed in an arm vein and directed into a cell separator machine. There, the white cells and stem cells are separated from the other blood components through a spinning process and collected in a bag inside the machine. The rest of the blood is returned to the donor through a catheter in the other arm.