• IL-6;
  • hormonal imprinting;
  • Tetrahymena;
  • uptake;
  • localization;
  • secretion


The unicellular Tetrahymena and its medium contain immunoreactively interleukin 6 (IL-6)-like molecules (hereinafter IL-6) in a measurable quantity in the 24 h-old cultures. This protozoan takes up exogenously supplied IL-6 very quickly, and this can be found in similar amounts in both the cells and the media after 1h. After 24h (48h cultures), an equal amount of IL-6 is present in the control and IL-6-treated cells and their media. By 120h, cells which have not had their medium changed retained the same quantity of IL-6 as the control; however less than half was found in IL-6-treated cells. In the medium of 120h-old cultures, there was a reduction of IL-6 content relative to the 24h content in the control; however, in the IL-6-treated cell culture medium, less than half of the level in the controls was found. Confocal microscopy demonstrated the localization of IL-6 in/on the oral apparatus and basal bodies, and the nuclear envelope also showed moderate labelling. IL-6 antibody binding was enhanced after IL-6 pretreatment (hormonal imprinting). The experiments call attention to the presence of an IL-6-like molecule and its uptake at a very low level of phylogeny.