IMMUNOHISTOCHEMICAL LOCALIZATION OF ARTICULAR-CARTILAGE PROTEOGLYCAN AND LINK PROTEIN INSITU USING MONOCLONAL-ANTIBODIES AND LECTIN-BINDINGMETHODS

Lectins have specificity for certain carbohydrate structures in macrom olecules. Lectins are, therefore, useful histochemical tools for demon strating the composition and localization of components of connective tissue matrices, such as articular cartilage. In order to assess the s ignificance of observed lectin-binding patterns, experiments were perf ormed in which monoclonal antibodies against chondroitin sulphate- and keratan sulphate-containing proteoglycans and link proteins were appl ied to sections of bovine articular cartilage after enzymatic digestio n with chondroitinase ABC and keratanase. The following conclusions we re made: (1) Binding of peanut agglutinin (PNA) in the interterritoria l matrix predominantly indicates the presence of keratan sulphate, but may also detect O-linked oligosaccharides of proteoglycans. (2) In no rmal cartilage wheat germ agglutinin (WGA) binds nearly exclusively to keratan sulphate. In cartilage degraded with chondroitinase ABC and k eratanase this lectin may also detect carbohydrates in link protein du e to enhanced accessibility. Binding of WGA to O-linked oligosaccharid es may eventually occur. (3) In enzymatically digested cartilage matri x, staining with soybean agglutinin (SBA) may be due to link protein, but not to chondroitin sulphate, because specific breakdown of the gly cosaminoglycan chain is required for binding of SBA. (4) Ulex europaeu s agglutinin I (UEA I) binding sites are only detectable in digested c artilage matrix.