Adhesion of U937 cells to the substrate pretreated with soluble fibrinogen: effect of the treatment time. Microtiter wells were coated with 2.5 μg/mL fibrinogen for 3 hours at 37°C, coated afterward with PVP, and washed with PBS. Aliquots (100 μL) of ¹²⁵I-labeled fibrinogen (5 μg/mL, 12 00 cpm) were added to the wells and incubated for various times at 37°C. After washing with PBS, U937 cells or buffer were added for 25 minutes at 37°C, and adhesion (•) or bound ¹²⁵I-fibrinogen (○) were determined. The data shown are the means ± SEs of 3 experiments with triplicate determinations in each experiment.