Figure 3

HL60 differentiation exhibits bimodal response to both the duration and concentration of stimulant. HL60 cells were cultured in 0.75% DMSO for 1 to 7 days (d) (A,B) or exposed to different doses (0% to 1.1%) of DMSO for 7 days (C,D) and monitored by Western blotting (A,C) and flow cytometry (B,D). Western blot analysis of whole cell populations revealed a gradual increase in intensity of the CD11b band both over time (A) and in response to increasing concentrations (C) of DMSO. In contrast, single cell analysis using flow cytometry demonstrated bimodality, as indicated by a shift of "peak heights" of the CD11b^Low (left arrows) and CD11b^High (right arrows) subpopulations in the histogram with increasing time of treatment (B) or dose of DMSO (D).