Much of the enthusiasm for exploiting CAR-modified IECs in AML, however, comes from their success in the management of various B cell malignancies where CD19-directed CAR T cell and, most recently, natural killer (NK) cell products have shown exquisite efficacy without the risk and associated morbidity and mortality of graft-versus-host disease (GVHD) intrinsic to allogeneic HCT. This evidence concerns the gene CD19 and graft versus host disease.