CD28 and acute myeloid leukemia: A previous study demonstrated that CAR T cells with gemtuzumab scFv and 4-1BB had relatively lower efficacy in AML mice than other scFvs, but the change to CD28 costimulatory domain improved the efficacy56, and the previous clinical trials on CD33 CAR T cells with different scFvs uniformly showed incapability to induce disease remission and little expansion7,8.