Before the transplant procedure, participants will undergo additional tests and procedures, including blood studies, 24-hour urine collection, infectious disease consultation, tuberculin skin test, PAP smear for women, chest X-ray, brain and hip MRI studies and DEXA-scan to evaluate bone density. In addition, patients may undergo leukapheresis to obtain white blood cells for study. For this procedure, whole blood is drawn through a needle in an arm vein and passed through a cell separator machine. The white cells are collected for removal, and the rest of the blood is returned to the body through the same needle or another needle in the other arm.