Competition of SSL5 with P-selectin/Fc binding to CHO–PSGL-1 cells. (A) CHO–PSGL-1 cells were incubated with 0.3 to 10 μg/mL SSL5 (•), SSL7 (♦), or PSGL-1 mAbs PL1 (▪), PL2 (▴), or KPL1 (▾) for 30 minutes on ice. After washing, the cells were treated with 1 μg/mL P-selectin/Fc. Bound P-selectin/Fc was detected with FITC-conjugated goat anti–human IgG. The data represent relative binding of P-selectin/Fc compared with control-treated cells and are mean values ± SEMs of 3 independent experiments. (B) Representative histograms of panel A depict binding of 1 μg/mL P-selectin/Fc to CHO–PSGL-1 cells in the absence (thin continuous line) and presence of 5 mM EDTA or 30 μg/mL anti–P-selectin mAb WASP12.2 (thick continuous line). Gray histograms represent cells stained only with the secondary antibody.