- To estimate the incidence of donor derived neutrophil engraftment by day +42 post-transplant for participants with high-risk hematologic malignancies undergoing a total lymphoid irradiation (TLI)-based hematopoietic cell transplantation (HCT) using a T cell depleted (TCI) haploidentical donor peripheral blood stem cell (PBSC) donor combined with an unrelated umbilical cord blood (UCB) donor.