We have used two monoclonal antibodies, 128C3/3 and 504B1, to immunolocalize their carbohydrate epitopes in different developmental stages of Schistosoma mansoni. Both epitopes contain fucose: mAb 128C3/3, as we have shown previously, recognizes fucose in a novel, possibly internal linkage (Levery et al. 1992) while mAb 504B1, as we show here, bound to the Lex epitope, which contains fucose α1 → 3 linked to N-acetyl-glucosamine. The tissue expression of these epitopes was strikingly different and both elicit an immune response in infected hosts. The mAb 128C3/3-defined epitope was exposed on the surface of all larval stages but not on adult worms; however, it was found in the excretory system of adult worms of both sexes. In contrast, surface expression of the Lex epitope was initiated after the transformation of cercariae to schistosomula and was maintained throughout the adult life in both sexes.
