Time-dependency of cytokine-stimulating effect on CD34⁺ cell adhesion to HA. Adhesion assays were performed in the presence of 10 ng/mL (•) SCF and (▪) IL-3 and 0.1 ng/mL of (▴) GM-CSF. (♦) Cells preincubated at 4°C for 15 minutes with 5 μg/mL of the anti-CD44 MoAb H90. (▾) Cells treated with the same dose of IgG1 in the same conditions. Cell adhesion was measured at 15 minutes, 30 minutes, and 2 hours. Measures were performed in triplicate as indicated in the legend to Fig 1. Data are means ± 1 SE calculated from three independent experiments.