Abstract
Pre-treatment of L cells with 750 units/ml of mouse interferon depressed the yield of interferon when the cells were treated with Newcastle disease virus (NDV). The refractory state persisted for more than 5 days. Nucleated fragments (karyoplasts) obtained by cytochalasin B-induced enucleation were made from such interferon pre-treated cells; cells reconstituted from these karyoplasts produced less interferon in response to NDV than did cells reconstituted from karyoplasts derived from untreated cells. The source of the enucleated cytoplasm (cytoplasts) used in the cellular reconstitutions did not affect the yields of interferon.