Patients with severe, refractory aplastic anemia have a severe, life threatening disease in their bone marrow. Refractory disease means that disease has come back or not responded after receiving one or more immunosuppressive treatments. High dose chemotherapy followed by bone marrow transplantation (BMT) has been used to treat blood diseases like aplastic anemia but complications from Graft vs Host disease (GVHD) and graft failure have limited the survival for those patients.