CD19 and cancer: Here, using a CD28 costimulatory domain-containing CAR design, as used in clinical trials of both CAR NK [10, 11] and CAR T cells [13, 14], we report significantly reduced CAR-mediated IFN-γ production and cytotoxicity after acute and chronic CAR stimulation by CAR NK cells compared with CAR T cells against various CD19 positive cancer cell lines in vitro in a head-to-head comparison.