Chemotaxis of human ATL cells in response to SDF-1α. (A) The migration assay of human ATL cells freshly prepared from frozen stocks of ATL patient's peripheral blood mononuclear cells and cultured for 2 days. Human ATL cells were also examined for chemotactic activity in response to SDF-1α, using recombinant human SDF-1α. After incubation with SDF-1α for 2.5 hours, the number of the cells migrating to the lower chamber was counted using a hemocytometer. (B) Phosphorylation of ERK1/2 after stimulation with SDF-1α (100 ng/mL for 5 minutes) in human ATL cells with or without AMD3100 pretreatment (25 μg/mL for 1 hour). (C) The inhibitory effect of AMD3100 on the migration of human ATL cells. Human ATL cells were preincubated for 60 minutes with the indicated concentrations of AMD3100, and then applied to the migration assay in the presence of 100 ng/mL SDF-1α. The number of the migrating cells was counted, and represented in the bar graph as a relative ratio of migrated to nontreated cells.