Cytochemical studies of lectin binding by diseased human muscle

The binding characteristics of lectins with varying sugar specificities were investigated in muscle biopsies from normal individuals and from patients with neuromuscular disorders. Horseradish peroxidase (HRPA) and fluorescein isothiocyanate (FITC)-conjugated lectins were used for light microscopy and ferritin-conjugated Concanavalin A (Con A) for electron microscopy. In normal and diseased muscle a lectin specific for alpha-D-mannosyl residues (Con A) and a group of lectins specific for beta-D-galactosyl residues were found to bind to the perimysial and endomysial connective tissue, blood vessels and capillaries and clearly demonstrated the perimeter of each muscle fibre. Wheat germ agglutinin (WGA), specific for N-acetylglucosamine and N-acetyl-neuraminic acid residues, had a similar distribution of staining although it appeared to stain the capillaries more strongly. In contrast, lectins specific for alpha-L-fucose and N-acetyl-galactosamine did not stain specifically any structures in normal or diseased muscle. In biopsies from dystrophic patients Con A, WGA and the beta-D-galactose specific lectins were always associated with splits and in biopsies from a variety of disorders discontinuities in staining were observed at the periphery of occasional fibers. These were not found in normal muscle. Electron microscopy showed Con A bound to the basement membrane of muscle fibres and capillaries and the connective tissue. The plasma membranes themselves were unstained. These preliminary investigations of lectin binding in muscle have shown important differences in diseased muscle and demonstrate the application of lectin chemistry to the study of membrane structure.