Time course of endothelial cell E-selectin expression induced by anti–annexin A2 mAb or β₂GPI and anti-β₂GPI antibodies. Endothelial cells were cultured in 96-well microplates and prepared as described in “Materials and methods,” then incubated for increasing time intervals with either β₂GPI (100 nM) and rabbit anti-β₂GPI antibodies (600 nM; ▪ and solid line), or anti–annexin A2 mAb alone (600 nM; ▴ and dotted line). Cell surface E-selectin expression was then determined by ELISA. Error bars represent the mean plus or minus SEM of quadruplicate points. This experiment is representative of 2 so performed.