PROBLEM: Interferons (IFN) have been shown to be secreted by the trophectoderm of implanting embryos in different species, in particular ungulates. In the pig, a clear-cut IFN-γ production, the role of which is unknown, was found in the trophoblast at implantation. A murine counterpart to these IFNs has not yet been identified.
METHOD: Two sets of experiments were conducted to test the presence of IFN-γ in the mouse conceptus. First, day 4 blastocysts were collected from Swiss mice and their antiviral activity measured in a microassay using mouse L 929 cells and vesicular stomatitis virus (VSV) in the presence or absence of anti-IFN-γ antibodies. In a second set of experiments, uteri from Swiss mice on days 5.5 and 6.5 of pregnancy were flushed and the resulting fluids assayed in a specific and sensitive ELISA test.
RESULTS: In the antiviral assay, no consistent IFN-like activity was found. The viral challenge also revealed a high susceptibility of mouse blastocysts to VSV infection. By ELISA, all but two samples (N = 75), whether on 5.5 or 6.5, were found negative.
CONCLUSION: We conclude that in this rodent species IFN-γ is most probably not involved in early maternal-fetal interactions.