To understand whether the CTLA-4positive anti-CD123 CAR T cells could exert cytotoxic effects and whether they could negatively affect the function of CTLA-4negative anti-CD123 CAR T cells, CTLA-4positive, CTLA-4negative, or an equal amount of either cell phenotype were cultured with AML cells and the cytotoxic and proliferative capacity was investigated. Here, IL3RA is linked to acute myeloid leukemia.