Endogenous SDF-1 improves PB Inc⁻CD34⁺ autonomous cell survival.

(A) PB CD34⁺ cells purified immediately after density gradient separation (Inc⁻) or (B) after incubation on a plastic support (Inc⁺) were incubated (1 × 10⁵ cells/mL) for 48 hours under apoptosis-inducing culture conditions (serum- and cytokine-free medium [IMDM]). The role of endogenous SDF-1 was evaluated by adding an anti–SDF-1 neutralizing antibody (10 ng/mL) to the culture. Freshly isolated cells and cells harvested after a 48-hour incubation were processed for apoptosis assessment by using the annexin-V apoptosis detection kit as indicated in “Materials and methods.” The percentages of annexin-V⁺ PI⁻ apoptotic cells and annexin-V⁺ PI⁺ necrotic cells shown for each histogram are for one experiment representative of the 3 performed.