Glycans with N-acetyllactosamine type 2-like residues covering adult Schistosoma mansoni, and glycomimesis as a putative mechanism of immune evasion.
Glycans at the surface of adult Schistosoma mansoni were investigated with gold-labelled lectins. The fragile complex of the glycans with the outer membranes could be preserved for electron microscopy by avoiding extensive pre-fixation with aldehydes and by introducing osmium-ferrocyanide as a membrane fixative. Male and female worms were entirely covered with glycans that intensely bound lectins from Erythrina cristagalli and Datura stramonium, suggesting that galactose(beta 1-4)N-acetylglucosamine residues occur in high numbers in the surface glycans. Similar staining was obtained with lectins from Triticum vulgaris, Glycine max and Ricinus communis agglutinin I, which react with N-acetylglucosamine or terminal galactose residues and bind non-selectively with high affinity to N-acetyllactosamine. Fucose, N-acetylgalactose and sialic acid were not detected with lectins and sialidase treatment. The tegument contained an abundance of glycans with the same lectin reactivities as the surface-expressed molecules, indicating that the worms synthesize and replenish their surface glycans and do not merely adsorb host substances. Glycomimesis is discussed as a mechanism of immune evasion in view of N-acetyllactosamine being a common and weakly immunogenic component in glycans of vertebrate hosts. S. mansoni might disguise themselves with the glycans against attack by immune effectors.
Schmidt
J
J
Division of Morphology and Cell Biology, University, Düsseldorf, Germany.
D000606:Amino Sugars / Q000276:immunology / Q000378:metabolism*; D000818:Animals; D001665:Binding Sites; D002240:Carbohydrate Sequence; D002462:Cell Membrane / Q000737:chemistry / Q000276:immunology / Q000378:metabolism; D006224:Cricetinae; D005260:Female; D037102:Lectins; D008297:Male; D051379:Mice; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D011134:Polysaccharides / Q000737:chemistry / Q000276:immunology / Q000378:metabolism*; D012550:Schistosoma mansoni / Q000276:immunology / Q000378:metabolism* / Q000648:ultrastructure
D000606:Amino Sugars; D037102:Lectins; D011134:Polysaccharides; C000458:N-acetyllactosamine