Related to this, our finding that a certain high affinity CAR expression level results in the separation of the anti-tumor effects of CD38-CAR T cells from their off-tumor cytotoxicity is also novel and suggest that quantitative manipulation of CAR surface expression could, next to CAR affinity optimization, also be exploited to increase the tumor selectivity of CARs directed against tumor-associated antigens (TAAs). Here, CD38 is linked to neoplasm.