IME -- an inhibitor of interferon activity isolated from mouse embryonic tissues. II. Biological characteristics

The biological properties and mode of action of IME were studied. Extracts of homogenized and lyophilized mouse embryos served as source of IME, which was found to be localized mainly in cells of mouse amnionic membranes and embryonic tissues. Growth of embryos was accompanied by falling activity of the inhibitor. IME activity was manifested only if it acted on cells in established antiviral state, and only in systems with efficient protein synthesis in all stages. IME stimultes cell metabolism. The findings from this study constitute material for further research on factors antagonistic to interferon.