Immunological Determinants of Proteoglycans

Bovine nasal cartilage proteoglycan monomer which had been digested with chondroitinase ABC to form the keratan sulfate-protein core was injected into rabbits. High titer antiserum was obtained as judged by the binding of 1261-labeled keratan sulfate-protein core. Native proteoglycan did not inhibit the interaction of the antiserum with labeled keratan sulfate-protein core. However, the disaccharide obtained from chondroitin 4-sulfate by the action of chondroitinase ABC, 2-acetamido-2-deoxy-3-O-(/3-~-gluco-4-enepyranosyluronic acid)-4-O-sulfo-~-galactose, inhibited the interaction 50% at a concentration of 500 PM. The corresponding 6sulfated and nonsulfated disaccharides at the same concentration gave 15% and 10% inhibition, respectively. Chondroitinase-digested proteoglycan from Swarm rat chondrosarcoma was strongly inhibitory, while the hyaluronidase-digested chondrosarcoma proteoglycan exhibited no detectable inhibition. Evidently, the antiserum raised against chondroitinase ABC-digested bovine nasal cartilage proteoglycan contains antibodies which recognize the unsaturated uronic acid residue linked to N-acetylgalactosamine 4-sulfate. These antibodies will be valuable for identifying and quantitating chondroitin 4-sulfate-containing proteoglycans in tissues.