Partial Purification of a Placental Interferon with Atypical Characteristics

Extracts of normal, term placentas, from NIH Swiss mice, were prepared in hypertonic buffer, assayed for interfereon (IFN-Pl), and fractionated by exclusion chromatography on Bio-Gel P-100. Two peaks of IFN-like activity were identified by species specific suppression of virus-induced cytopathic effects (CPE). Peak 1, with an estimated molecular weight in excess of 70 kD, was destroyed by acid treatment (pH 2), trypsin, and heat (56°C/15 min). Peak 2 has an estimated molecular weight of 27 kD, is partially resistant (50%) to acid treatment (pH 2), but is inactivated by trypsin and heat. IFN in unfractionated placental extracts, as well as in Peak 1 but not in Peak 2, is partially neutralized by antibody to type I (α,β), but not by antibody to type II (γ) IFN. Neutralization of IFNPl by anti-type I antiserum required concentrations in excess of 100 times greater than those needed to neutralize L-cell IFN an equivalent degree. These investigations suggest that the murine placenta contains at least two speci...