Ultrastructural localization of the circulating cathodic antigen in the digestive tract of various life-cycle stages of Schistosoma mansoni.

In the present study the ultrastructural localization of the schistosome-derived circulating cathodic antigen (CCA) within the digestive tract of various life-cycle stages of the blood fluke Schistosoma mansoni has been determined. Use was made of CCA-specific monoclonal antibodies in a two-step gold-labeling procedure. The following results were obtained: In cercariae gold label was found in the cytoplasm and in the luminal surface coat of the gut epithelium. The oesophagus of this life-cycle stage of the parasite showed minimal CCA reactivity, as gold label was limited to the luminal surface coat, locating proximally to the gut. In 3 1/2-week-old worms and in adult male and female worms CCA was demonstrable in the Golgi apparatus, in cytoplasmic vesicles and in the luminal surface coat; in the caudal quarter of the gut of adult worms CCA was also present in lysosome-like bodies. The oesophagus of these worm preparations did not show any CCA reactivity. In miracidia CCA was not present.