Fig. 4. Cell type-specific inhibition of FN-stimulated haptotactic migration by fibulin-1. The undersurfaces of Transwell membranes (8 µm pores) were coated with FN (100 µg ml^–1), unoccupied sites were blocked with BSA and were then incubated with fibulin-1 or BSA (100 µg ml^–1 each). Cells (1x10⁵) in sfDMEM were added to the upper chambers of inserts placed in wells containing sfDMEM plus fibulin-1 or BSA (50 µg ml^–1 each). After 18 hours of incubation at 37°C, 5% CO₂, the number of cells that had migrated to the undersurface of the membranes was determined. The plotted values are means ± the standard deviations of cell counts from five independent optical fields from triplicate experiments. The results shown were obtained using fibulin-1 isolated by monoclonal antibody 3A11 IgG-Sepharose. Similar findings were obtained using fibulin-1 isolated with a monoclonal antibody 5D12 which binds to an epitope distinct from that of 3A11 (data not shown).