CAR NK cells were highly efficient at killing CD19-positive targets such as Raji, Daudi, and primary CLL cells (44) and were superior at exerting antitumor activity in a xenograft mouse model of lymphoma compared to CAR NK cells expanded with a previously reported K562-derived APCs (C9/IL-21) expressing 4-1BBL and mbIL21 only (15), supporting the notion that a three-signal model of NK cell activation can support expansion of NK cells with greater potency. Here, IL21 is linked to B-cell chronic lymphocytic leukemia.