Fig. 4. CD11b and nitroblue tetrazolium (NBT) reduction analysis in cultured cells treated with 0.1 m M all-trans retinoic acid (ATRA) and 0.25 m M As₂O₃ individually or in combination for 1 to 3 days. CD11b-positive cells by fluorescence-activated cell sorter (FACS) analysis in the NB4 cell line (A) and in primary acute promyelocytic leukemia (APL) cells (B). NBT reduction analysis of NB4 cells (C) and of primary APL cells (D) .