Strategy of combined IUHSCTx and minimally myeloablative same-donor postnatal SCT. This strategy presupposes the use of adult-derived donor cells and is dependent on specific tolerance induction and, presumably, the establishment of at least minimal donor HSC engraftment. Methods to improve the efficiency of tolerance induction such as cotransplantation of donor-derived antigen-presenting cells (APCs) may prove useful in the future. If effective, this strategy could be rationally applied to diseases ameliorated by low or moderate levels of mixed hematopoietic chimerism and, potentially, to any disease effectively treated by postnatal SCT in which a matched sibling donor is not available.