Electron microscopy of Trichomonas vaginalis Donné: interaction with vaginal epithelium in human trichomoniasis

Light and electron microscopic examination of portio biopsies from eleven patients with trichomoniasis vaginalis revealed in four patients clusters of cells of T. vaginalis (T. vag.) which were attached to the vaginal mucosa. The minimum gap between adjacent trichomonad cells was the size of gap junctions (2 nm). Cells of T. vag. invaded superficially located epithelial cells but did not penetrate to the deeper cell layers of the epithelium. The latter, however, were frequently infiltrated with neutrophilic granulocytes. Contact between cells of T. vag. and neutrophils was not observed. Trichomonads which were attached to epithelial cells contained a dense network of cytoplasmic microfilaments in the part of the cell which came into contact with the epithelium. The remaining part contained the organelles normally seen in T. vag.. Endocytotic cell activity of amoeboid T. vag. occurred from the free cell surface only. A cell coat on the cell membrane--formed by bristles--was confined mainly to pinocytotic invaginations. Glycogen granules which were absent from the larger part of the epithelium were densely packed in the trichomonad cells. The findings in this study indicate that the interaction between the cells of T. vag. and the vaginal epithelium takes place primarily at a distance probably by means of substances released into the vaginal fluid, and secondly by a direct cell contact mechanism.