The optimal CD3+ cell dose to be used for allo HSCT is unknown. In addition, there are multiple variables in addition to CD3+ cell dose which affect engraftment, immune reconstitution, GVH and GVL in these patients including recipient age, diagnosis, disease status at transplantation, donor/recipient tissue type match, preparative regimen, and GVHD prophylaxis. Thus the ability to produce products with a fixed CD3+ content is critical to further research and ultimately to the definition of the "right dose" of CD3+ cells for various clinical situations.