Glycosaminoglycan Binding Assays

The interaction of a select group of chemokines with glycosaminoglycans has been demonstrated previously, both by affinity coelectrophoresis (1 ) and by cell-surface binding assays and immobilized binding heparin assays (2 ). The significance of the interaction of chemokines with glycosaminoglycans has been demonstrated for a limited subset of chemokines. A first example is the interaction of heparin with Platelet Factor 4, resulting in the neutralization of the anticoagulant property of heparin (3 ). Secondly, using both immobilized heparin and cell-surface proteoglycans, it has also been demonstrated that chemokines oligomerize on proteoglycans. This oligomerization on solid surfaces can cause an increase in the local concentration of chemokine, which in turn affects the interaction of the chemokine with adjacent high affinity cell-surface receptors (2 ). More recently it has been demonstrated that the cell-surface proteoglycans on T cells play a role in the regulation of the anti-HIV-I activity of RANTES. Removal of cell-surface heparin sulfate, but not chon-droitin sulfate from a human T-cell line, rendered the cells resistant to the antiviral effects of RANTES (4 ). These authors demonstrate the importance of understanding the interaction of different chemokines with different proteoglycan types, since a chemokine may not bind all proteoglycans equally.