CD44 is the primary cell surface receptor for the extracellular matrix glycosaminoglycan
hyaluronan. Here we determined the relative avidities of unlabeled hyaluronan preparations
for cell surface CD44 by their ability to block the binding of fluorescein-conjugated
hyaluronan to a variety of cells. We show that hyaluronan binding at the cell surface is a
complex interplay of multivalent binding events affected by the size of the multivalent
hyaluronan ligand, the quantity and density of cell surface CD44, and the activation state of …