Bimodal distribution of bcl-2 protein expression (bcl-2^low and bcl-2^high) in primitive hematopoietic precursors and their progeny. Mononuclear cells (MNCs) were stained with membrane antigens (CD34-tri-color and CD38-PE), then permeabilized with Ortho Permeafix and stained for anti-bcl-2 FITC. Cells were analyzed according to CD38 intensity level, CD38^−/low (R3), CD38²⁺ (R4), and CD38³⁺ (R5) by using only the strong CD34 positive cells (Fig 1C). These selected gates were identically used for analyzing all samples. MNCs were also permeabilized and stained with mIgG to define the threshold between bcl-2-positive and bcl-2-negative cells. Similarly, the granulocytes from whole, fresh MPB samples were also analyzed. The bcl-2 gates (bcl-2^low and bcl-2^high) were decided by the histograms distribution. (A) The bimodal distribution of bcl-2 in MPB, CB, and BM. (B) The comparison in bcl-2 fluorescent intensity between the mature granulocytes and the hematopoietic precursors (CD34^s+/CD38^−/low) seen in Fig 2A.