SDF-1 increases SCF-induced tyrosine phosphorylation in PB Inc⁺ CD34⁺ cells.

PB and BM CD34⁺ cells purified after incubation on a plastic support (Inc⁺) were pretreated without (control) or with SDF-1 (0.05 ng/mL) for 20 hours in serum- and cytokine-free medium (Stem α A) at a density of 5 × 104cells/mL. Cells were harvested, washed by centrifugation, and stimulated, with SCF (10 ng/mL) or IL-3 (10 ng/mL), for 5 to 15 minutes at 37°C. The time course of total tyrosine phosphorylation was detected by flow cytometry after intracellular anti-phosphotyrosine labeling. Histograms from a typical donor are presented. The MFI (AU) of positive cells for phosphotyrosine are shown for each histogram.