A method of inducing patient anti-donor unresponsiveness in a patient undergoing stem cell transplantation by subjecting the patient to a non-myeloablative/lymphoablative (-/L) conditioning regimen comprising the following steps:
- (i) treating the patient with a compound that is lymphoablative (L) and eliminates substantially all functioning T lymphocytes of patient origin while allowing the patient to retain a functional population of hematopoietic stem cells;
- (ii) administering a donor-derived preparation of allogeneic stem cells to said patient;
- wherein said conditioning regimen results in patient donor-specific unresponsiveness and survival of the transplant.