Growth inhibition of Toxoplasma gondii in cell cultures treated with murine type II interferon.

In vitro assessment was made on the effect of murine Type II interferon (IFN) on the multiplication of Toxoplasma (T.) gondii in mouse cell cultures. Macrophages and L cell cultures treated with Type II IFNs prepared specifically from the spleen cell cultures of Toxoplasma- or BCG-infected mice markedly suppressed the growth of T. gondii. The enhanced antitoxoplasma activities of these IFN-treated cells were nonspecific and of identical degree, and dependent on both IFN concentration and period of incubation in IFN preparations. Pretreatment with 500 U of Toxo-IFN for 24 hr before infection with Toxoplasma resulted in a. significant decrease in percentage of infected cells and number of intracellular parasites in 1 and 2hr postinfection. However, these IFNs conferred an enhanced antitoxoplasma activity on macrophages more effectively than in L cell cultures, and the activity of the activated macrophages and that of L cells seemed to be somewhat different each other; the growth inhibitory effect of the activated macrophages was microbicidal, whereas that of L cells was only microbiostatic and transient.