Abstract: 　Objective To study interaction between Trichomonas vaginalis and epithelium of genital tract of host as well as the pathogenesis of T vaginalis . Methods Immunohistochemical technique was used to observe the adhering process of T vaginalis to vaginal mucosa in rats by transmission and scanning microscopy. Results T vaginalis were shown to be PAS positive and clusters of T vaginalis were found to adhere to columnar epithelium rich in mucopolysaccharide on the surface of vaginal mucosa as viewed in sections of the middle and upper parts of the orgen. T vaginalis was positive for cathepsin. And the membrane of epithelial cells was often damaged by the released hydrolase.The parasite was also positive for actin;the microfilament bundles were arranged in reticular form in ameboid T vaginalis . The latter would penetrate between epithelial cells,and its filiform pseudopodia would invade the interspace of microvilli of the epithelium,to encircle and gradually phagocytize microvilli. Digitiform pseudopodia would insert between epithelial cells and encircle part of them.A few T vaginalis were found to adhere to the keratinized epithelium between mucosal folds as shown in the sections of the lower part of vagina. Conclusion T vaginalis is inclined to parasitise vaginal fornix because the superficial epithelial cells there are rich in mucinogen granules and abundant microvilli exist. After adhering, T vaginalis releases hydrolase to digest and phagocytize epithelium,which may directly damage the epithelium of the genital canal. Moreover, T vaginalis would take in mucopolysaccharide to affect the normal clearance process of vagina,resulting in inflammation of parasitized tissue.The cytoskeleton,cell coat,polymorphism of pseudopodia and lysosome of T vaginalis play an important role in the courses of movement,adhesion, encirclement,phagocytosis and digestion.

Key words: Trichomonas vaginalis, rat vagina, ultrastructure, immunohistochemistry, hydrolase, pathogenesis