[Toxoplasma gondii: ultrastructural study of cystic formations observed in human fibroblast culture].

A strain of Toxoplasma gondii, non pathogenic to mice (Prugniaud strain) produced cyst-like stages when inoculated in human fibroblast culture. An ultrastructural study was performed in order to compare these cyst-like forms to brain cysts of the same strain and to intracellular clusters of tachyzoites observed in mice TG 180 sarcoma cells. Electron microscopy confirmed the similarities between brain cysts and cysts obtained in vitro.