Evaluation of TRAIL activity on freshly isolated PB CD34⁺ cells.

The percentage of cell death was evaluated in CD34⁺ cells treated with irrelevant IgM mAb and rHis6-tag peptide (CONT), TRAIL, or anti-CD95 (CH 11) IgM mAb for 20 hours in medium supplemented with (CYTOK, right panels) or without SCF + IL-3 (left panels). CD34⁺ cell death was detected by either FSC/SSC (upper 2 panels) or PI staining (lower 6 panels) analyses. Percentages of dead cells are indicated in each panel. Representative FSC/SSC analyses are shown only for control (CONT) cultures, since similar profiles were observed in TRAIL- and anti-CD95-treated cells (not shown). In the lower 6 panels, quadrants were set based on negative controls stained with isotype-matched irrelevant mAb (not shown). X-axis: relative CD34 expression; Y-axis: propidium iodide staining.