This is a single-arm, open label, single institution, compassionate study which will enroll patients who are marginally engrafted and transfusion and/or growth factors dependent after allogeneic hematopoietic stem cell transplant (HSCT) regardless of the underlying disease for which the transplant was performed. Study subjects will receive a "booster" infusion of CD34+ cell selected and T-cell depleted G-CSF mobilized apheresis product from the original stem cell donor in order to improve engraftment. The "booster" infusion will be administered without prior conditioning.