Unusually large interferon-alpha-like mRNAs and high expression of interleukin-6 in human fetal annexes

Endogenous interferons (IFNs) with antiviral activity have been detected in human fetal annexes, without any apparent induction. Some are of unusually high molecular weight and antigenic properties (Duc-Goiran P., Robert-Galliot, B., Lopez, J., and Chany, C. (1985) Proc. Natl. Acad. Sci. U.S.A. 82, 5010-5014). We study here the expression of IFN genes from the three antigenically distinct groups, in placental tissues taken during third-trimester pregnancies. We show by Northern blot analysis with RNA probes that IFN-alpha-like transcripts correlate with the presence of functionally active protein, purified by immunoaffinity chromatography. We fractionate on a formamide sucrose gradient, identify, and characterize a large 4.3-kb IFN-alpha-like transcript, which may be specifically expressed during fetal development. Despite the absence of IFN-beta transcript, a protein with an antiviral activity which was neutralized with a polyclonal anti-IFN-beta serum was detected in the placenta and could be related to a beta-like IFN. Besides IFNs, various growth factors and cytokines can be found in the placenta. We report here the presence of interleukin-6 expressed at high levels in fetal annexes. The coexpression of Interleukin-6 and endogenous IFNs suggests that they play an important role during development.