Dose-dependency of cytokine-stimulating effect on CD34⁺ HPC adhesion to HA. Adhesion assays were performed in the presence of 0.1 to 10 ng/mL of (•) SCF, (▪) IL-3, or (▴) GM-CSF. Cell adhesion was measured at 15 minutes as described in the Materials and Methods. Data are means ± 1 SE calculated from three independent experiments.