Levels of CD34⁺ cell apoptosis and proliferation in different diagnostic subgroups.

To evaluate progenitor cell apoptosis, bone marrow mononuclear cells were isolated by density gradient centrifugation and incubated with phycoerythrin (PE)-conjugated anti-CD34 monoclonal antibody (Mab) and fluorescein isothiocyanate (FITC)-conjugated annexin V prior to 2-color flow cytometric analysis. Proliferating cells were identified by permeabilizing CD34-labeled cells and incubating with FITC-conjugated Ki-67 Mab. Percentage of positivity was determined by comparison of the fluorescence distribution histogram of positively stained cells to that of cells to which no annexin V was added for apoptosis, and to cells labeled with appropriate isotype control for Ki-67. As illustrated in the scatter plots, apoptosis (A) and proliferation (B) varied widely, even within diagnostic subgroups. (C) Bar chart that compares median levels of CD34⁺ cell apoptosis and proliferation in specific diagnostic categories.