Important questions remain about the functional and long-term status of transplanted SCD patients in a variety of areas; this study will focus upon immune function. Because little is know about the functional immune status of patients after non-myeloablative transplants, and certainly not those who undergo transplantation for the diagnosis of sickle cell anemia, patient blood samples will be analyzed for extent of immune reconstitution following transplant through immunophenotyping of various immune cell subsets, molecular analysis of reconstitution of T cell neogenesis (TREC analysis) and T cell receptor complexity (TCR Vbeta spectratyping).