Unusual apparently constitutive interferons and antagonists in human placental blood.

We have detected seemingly uninduced interferons (IFNs) in 29/37 human placental samples obtained during caesarian sections at different periods of pregnancy, mostly around the 37th week. The amounts were usually low and did not enable us to correlate our findings with any physiological or pathological conditions. Occasionally the presence of IFN was masked by a lectin-like antagonist. Therefore, in a number of cases, substantially higher amounts of IFN were found after purification by affinity chromatography using concanavalin A, Cibacron blue, or antiserum to IFN-alpha, each coupled to Sepharose. Analysis by sodium dodecyl sulfate/polyacrylamide gel electrophoresis revealed the presence of IFN-alpha and IFN-beta with molecular masses between 15 and 80 kilodaltons. Some of the high molecular weight components were neutralized either only by monospecific antiserum to IFN-alpha or, to the same extent, by antiserum to IFN-alpha or to IFN-beta, reminiscent of those previously reported after viral induction in the human amniotic membrane. We postulate that both IFNs and antagonist play a physiological role during fetal development.