Heparin-binding Properties of Human Serum Spreading Factor*

in blood did not bind to heparin under conditions of physiological ionic strength and pH. Human serum spreading factor (SF’) is a glycoprotein purified from serum or plasma that mediates effects on cell adhesion, spreading, migration, proliferation, and differentia- tion in a wide number of animal cell culture systems (1-27). SF is responsible for a significant portion of the total spread- ing-promoting activity of serum in cell culture experiments, and purified SF is active at promoting cell spreading at *