The localization of the 28 kDa Schistosoma mansoni glutathione S-transferase (Sm28 GST) has been investigated using immunohistochemistry and electron microscopy and the results compared with previously published data. This study confirms the wide distribution of this antigen in the parasite. In male and female worms, Sm28 GST is localized in the tegument, the parenchyma, the oesophageal epithelium and in genital organs. Sm28 GST was clearly detected in germinal and sustentacular cells. The decrease of staining intensity during the differentiation of germinal cells suggests a down-regulated expression of the molecule. At the ultrastructural level, this antigen was abundant in nuclei and less present in the cytoplasm. The marked heterogeneity observed in the staining of individual worms indicates that Sm28 GST seems to be closely associated with the parasite’s metabolism. The results are discussed in relation to the biological and protective functions of the protein.
