Lectin binding in human skeletal muscle: a comparison of 15 different lectins

Fifteen lectin-horseradish peroxidase conjugates have been used in a comprehensive histochemical study of human skeletal muscle. The staining patterns of many lectins were found to be coincident with the known distributions of types I, III, IV and V collagen, fibronectin and laminin. One lectin, Bandeiraea simplicifolia (BSA I), selectively stained capillaries in a blood group-specific manner, the significance of which is unknown. The results show that although lectins are useful cytochemical probes for identifying tissue glycoconjugates, lectin binding is not solely determined by monosaccharide specificity as lectins which interact with the same sugars may have completely different staining patterns. Factors such as accessibility, glycan conformation and oligosaccharide sequence also affect lectin binding in tissues. For these reasons, we conclude that a comprehensive histochemical investigation of tissue glycoconjugates should employ a large number of lectins, preferably with overlapping sugar specificities.

Binding of Ricinus communis I lectin to the muscle cell plasma membrane in diseased muscle

Using an electron histochemical technique, we have observed the binding of a D-galactose-specific lectin to the muscle cell plasma membrane in muscle biopsies taken from patients with various neuromuscular disorders. In spinal muscular atrophy, the only neurogenic disease studied, the plasma membrane stained as in normal muscle. However, in the myopathies Becker and limb-girdle muscular dystrophy and in the polymyositis there was a reduction in both the occurrence and the intensity of staining of the plasma membrane. Reduced lectin binding by the plasma membrane probably reflects secondary changes in the composition of glycoproteins and/or glycolipids in the membrane and seems to be common to all these myopathies to varying degrees.

Immunolocalization of complement component C9 on necrotic and non-necrotic muscle fibres in myositis using monoclonal antibodies: a primary role of complement in autoimmune cell damage

Monoclonal antibodies to human complement component C9 were used to localise the membrane attack complex (MAC) of human complement on muscle fibres from patients with autoimmune myositis. A pigeon erythrocyte 'model' system was used to screen the available monoclonal antibodies for their ability to bind C9 after its insertion into the MAC. Three of the five antibodies tested were demonstrated, using radioiodine- or rhodamine-labelled second antibody, to bind. The antibody giving maximum binding in this system was used to demonstrate that MACs were present on histologically normal as well as on necrotic fibres in myositis. No binding was seen in muscle from control subjects. These results suggest a primary role of complement in the pathogenesis of muscle fibre necrosis in myositis.

Altered binding of Ricinus communis I lectin by muscle membranes in Duchenne muscular dystrophy

Recently, it has become clear that a structural or functional abnormality of the plasma membrane may be involved in the pathogenesis of Duchenne muscular dystrophy (DMD). We have used a D-galactose specific lectin, that binds strongly to the muscle cell surface, to search for differences in sarcolemmal staining in biopsies from 5 normal and 7 DMD individuals. Electron optical studies revealed a dramatic and consistent decrease in lectin binding by the muscle plasma membrane in DMD. Although unable at this stage to identify the specific molecular abnormality responsible for this decreased staining, the results provide good evidence that a basic structural change within the plasma membrane may be intimately associated with DMD.

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.