Ephrin-A1 induces actin polymerization. CD4⁺ T cells were incubated with ephrin-A1 (•), SDF-1α (○), or the combination of ephrin-A1 and SDF-1α (▾) for the indicated times. The cells were then fixed, permeabilized, and stained with rhodamine-phalloidin for analysis by flow cytometry. SEM is shown for 4 different experiments.