Toxoplasma gondii: Human Interferon Studies by Plaque Assay 1

Abstract

Summary

In order to define the interaction of the human IF system with TG, a series of experiments examined the effects of human IF on TG growth in monolayers of HEF.

Neither leukocyte nor fibroblast human IF had any effect on TG plaque growth, in IF concentrations ranging from 10^-1 to 10⁴ units/ml, although appropriate IF activity was demonstrated in VSV plaque-reduction assays performed in parallel. Supernatant fluids from TG-infected cells, both HEF and peripheral human leukocytes, contained no detectable acid-stable IF activity, despite good induction of IF by NDV in parallel experiments. Supernatants from TG-infected cells contained no inhibitor of TG as assayed with TG plaques in HEF.

These experiments indicate a lack of interaction between TG and the classical IF system in cells of human origin, supporting the findings of Schmunis et al (14). It is clear that the observations in murine and chick models (6-8) cannot be directly extrapolated to humans, and that interactions of TG and the IF system are a function of the origin of the IF and of the cell system under study.