Bone marrow of SCLtTA/BCR-ABL mice has an expanded immature myeloid cell population. (A) Representative FACS profile of bone marrow cells from an induced double-transgenic (W202) and a wild-type animal. Cells were costained with PE-labeled Mac-1 and FITC-conjugated Gr-1, CD34, c-kit, or B220 antibodies, as shown. (B) (upper panel) Staining of the myeloid markers Gr-1 and Mac-1 in a single-transgenic SCLtTA mouse and a double-transgenic SCLtTA/BCR-ABL mouse (W185) after the induction of BCR-ABL following the withdrawal of tetracycline. R2 represents Gr-1+/Mac-1+ cells (neutrophils), and R1 represents Gr-1^lo/Mac-1+ cells (more immature myeloid cells). (lower panel) Percentage of Gr-1^lo/Mac-1+ cells as absolute values (R1) or as the fraction of these cells among all Gr-1+/Mac-1+- staining cells (R1/R1+R2). Both percentages proved to be significantly higher in double-transgenic mice compared with BCR-ABL (n = 8), SCLtTA (n = 1) single-transgenic, or wild-type animals (n = 2), which represented “control” animals shown in the figure. Values are shown as mean ± SD.