In a recent phase 1 and 2 trials, CD19-specific CAR-engineered primary NK cells have shown a tremendous clinical response in patients with relapsed or refractory CD19-positive non-Hodgkin’s lymphoma (NHL) or chronic lymphocytic leukemia (CLL) without the induction of typical CAR T cell-associated side effects such as cytokine release syndrome, neurotoxicity or graft-versus-host disease [14]. The gene discussed is CD19; the disease is graft versus host disease.