ABCA1 and acute promyelocytic leukemia: Moreover, in the presence of M2 macrophages, the cytotoxic effect of CAR19 cells on DB cells, but not CD19-negative acute promyelocytic leukemia cells (HL60 cells), was markedly inhibited compared with that in the control cells; however, it was restored by ABCA1 knockdown (Fig. 3g).