Interferon: protection of cells infected with an intracellular protozoan (Toxoplasma gondii).

Chick and mouse cell monolayers treated with interferon were significantly protected from destruction by toxoplasma. The results suggest that fewer numbers of organisms were released from interferon-treated cells. Interferons were uniformly more active in a viral assay than in a toxoplasma assay, and they had the same properties in both assays. The data suggest that interferon activity may be directed against organisms phylogenetically higher than viruses.