Adoptive cell immunotherapy (ACT) is a promising approach to treat a variety of pathological states, including infections as well as both solid and hematologic cancers. Immune cells in ACT can be harvested from tumor resection/biopsy, from the patient’s own blood, or donated by a fully or partially human leukocyte antigen (HLA)-matched healthy donor. These cells are then injected into the patient after minimal or more extensive ex vivo manipulations. The oldest, and arguably still one of the most effective forms of ACT, is allogeneic hematopoietic cell transplantation, which most often requires only minimal cell handling and primarily leverages immunogenetic disparities between donor and recipient to treat hematopoietic cancers