Penetration of chick embryo erythrocytes by toxoplasma gondii tachyzoites in simplified incubation media.

The ability of Toxoplasma gondii tachyzoites to penetrate chick embryo erythrocytes (CEE) and the extent of penetration were examined in various simplified, incubation media. Toxoplasma gondii penetrated CEE well in serum-free Eagle's minimum essential medium or in Hanks' balanced salt solution, but much less in phosphate buffered saline (PBS). However, the addition of glucose alone to PBS substantially increased the penetration. A similar effect was seen with other monosaccharides, except galactose. A further, marked increase in penetration was noticed if magnesium ion (but not calcium ion) was added to PBS containing glucose. The present results indicate that T. gondii can penetrate CEE well in simplified incubation solutions such as PBS only when magnesium ion and a monosaccharide are added. Their possible role is discussed in relation to cellular adhesiveness, because the adherence of the parasite to the host cell membrane may be the first step in the penetration process.