Following demonstrations of the remarkable efficacy of genetically-modified T cells in certain hematologic malignancies, e.g., frequent and durable response rates in B cell malignancies treated with CD19-directed chimeric antigen receptor (CAR) T cell trials [6–11], the field has grown tremendously, with an explosion of academic and commercial investigations using immune effector cells as a new platform of therapy. The gene discussed is CD19; the disease is hematologic disorder.