Figure 3. Keratan sulfate in emphysema and COPD.

(A) The structure of keratan sulfate, KS-1, L4 consists of galactose-6-sulfate unit and β1-4 linked to GlcNAc-6-sulfate. (B) A scheme for the potential protective functions of the keratan sulfate disaccharide L4 and derivatives thereof: triangle-L4 and pendant-L4 against emphysema and COPD. L4 shows anti-proteolytic activity caused by the inhibition of Mmp-2 and Mmp-9 activities. Triangle-L4 and pendant-L4 bind to Langerin more strongly than the L4 monomer and may result in an enhanced down-regulation of TNFα in dendritic cells. These two functions of L4 shown by squares contribute to the mitigation of emphysema phenotypes in the elastase-induced mouse model. The suppressed signal transduction through Langerin is not currently understood. Langerin is required for Birbeck granule formation. 6S: the sulfate group on carbon number 6.