DEMONSTRATION OF IMMUNOGENIC KERATAN SULFATE IN COMMERCIAL CHONDROITIN 6-SULFATE FROM SHARK CARTILAGE - IMPLICATIONS FOR ELISA ASSAYS

The prototype monoclonal keratan sulphate (KS) antibody 5D4 that is wi dely used for detection of KS in tissues and biological fluids reacts strongly with commercial low grade shark cartilage chondroitin 6-sulph ate, Characterization of the immunogenic material by chondroitinase AB C digestion, ELISA inhibition studies, immunoblotting and HPLC analyse s confirmed the presence of substantial amounts of KS, probably as a l arge: proteoglycan (>120 kDa), Commercial and heterogenic glycosaminog lycan preparations therefore must be used with great caution in immuno logical analyses. On the other hand the shark cartilage chondroitin 6- sulphate is an easy accessible source of immunogenic KS that can be us ed as a reference standard and as coating antigen in KS-ELISAs. The co ncentration of immunogenic KS in synovial fluid measured with an ELISA based solely on reagents of shark cartilage chondroitin 6-sulphate co rrelated well (r = 0.90) with the concentrations obtained with a tradi tional KS-ELISA that uses purified aggrecan as standard and coating an tigen, and KS in both serum and synovial fluid could be measured with sufficient linearity.