Who is the best donor for haploidentical stem cell transplantation?

Recent advances in haploidentical stem cell transplantation have enabled the use of human leukocyte antigen-half matched related donors for allogeneic stem cell transplantation and helped overcome one of the most important limitation in transplantation, which is donor availability, especially for the non-Caucasian population and mixed race individuals, extending allogeneic stem cell transplant for almost all patients in need. As many multiple potential related donors may now be available, it is increasingly clear that not all of these donors can provide equivalent transplant outcomes. Here we review the current available evidence of donor characteristics known to be associated with transplant outcomes for different types of haploidentical transplants using unmanipulated grafts (with post-transplant cyclophosphamide-based graft-vs-host prophylaxis and G-CSF and anti-thymocyte globulin approach) as well as modified grafts (with either selective or complete T-cell depletion). While various platforms use haploidentical donors, graft manipulation and approach to prevent graft-vs-host post-transplant may impact on donor selection and transplant outcomes.