L-selectin stimulation blocked CXCR4 down-regulation induced by SDF-1 on Jurkat cells. Jurkat cells were incubated with SDF-1 (500 ng/mL) in the presence or absence of fucoidan, sulfatide, or L-selectin cross-linking at 37°C for 1 hour. Representative histograms (A) and means ± SEM of relative fluorescence intensity of CXCR4 (% of control) from 3 experiments (B) are shown.