Fig. 2. TSG-6 properties and functions. TSG-6 binds specifically to GAGs, including HA, C4S and heparin and to the proteoglycan aggrecan. It also interacts, both covalently and non-covalently, with II: covalent complexes may be involved in crosslinking HA chains, whereas non-covalent interactions potentiate the anti-plasmin activity of II. TSG-6 has been implicated in cell proliferation, the inhibition of neutrophil migration and the regulation of CD44. The mechanisms of these activities remain to be elucidated.