Immunocytochemical localization of gut-associated circulating anodic antigen in Schistosoma japonicum

The localization of the gut-associated circulating anodic antigen in Schistosoma japonicum adults was revealed by means of the immunofluorescence and a peroxidase-anti-peroxidase method with the electron microscope. The reaction sites were confined to amorphous material in the cecal lumen. The cecal lumen generally was infolded with lamellae. The antigenic material appeared to be secreted by the rough endoplasmic reticulum, probably through the Golgi apparatus, into the lumen. Observations of male and female worms showed that there was a clear difference between the sexes in antigen concentration. The thick epithelium of the female worm, with well-developed cisternae on the endoplasmic reticulum, produced a lot more antigen than the male. Positive staining with ruthenium red confirmed that the antigenic material was a negatively charged polysaccharide as had been previously reported.