Effect of intact/nicked β2GPI on extravasation of HUVECs using a Matrigel-cell invasion assay in the presence or absence of AS4.5. Effect of intact or nicked β2GPI on the ability of HUVECs to migrate through a basement membrane-like extracellular matrix was evaluated in the presence or absence of AS4.5. HUVECs were added to the top wells of each chamber, and 10% FCS-enriched culture medium was added to each bottom chamber as a source of chemotactic factors. (A) In the top 2 lines of the panels, assays were done without AS4.5_. AS4.5 was added to the wells in the bottom 2 lines of the panels. Serial concentrations of intact β2GPI were added in lines 1 and 3, whereas nicked β2GPI was added in lines 2 and 4. Similar results were obtained in other 3 experiments (original magnification, ×100). (B) HUVECs migrated through the Matrigel, and 8-μM pores on the membrane were stained and counted using image processing software. Ratios of the numbers of the HUVECs migrated under treatment with reagents against the number of those cells without any additional reagents were plotted on the graph. Concentrations of intact/nicked β2GPI were as follows: 0.05, 0.2, 0.4, 1.0, or 4.0 μM. Error bars represent SE. Invaded cell counts in the presence of AS4.5 alone (50 nM)* were compared with those in the presence of both AS4.5 (50 nM) and nicked β2GPI (0.4 μM; **P = .027; Student t test).