In vivo immunosuppressive effects of recombinant ovine interferon-tau (trophoblastin): r.oTP (r.oIFN-tau) inhibits local GVH reaction in mice (PLN assay), prevents fetal resorptions, and favors embryo survival and implantation in the CBA/J x DBA/2 mice combination.

Problem: Ovine trophoblastin protein, be it natural or recombinant (oTP,r.oTP), a member of the tau interferon family (r.oIFN-tau), has been shown to possess immunosuppressive properties in vitro. It acts as a cytostatic agent across species. Indeed, it was immunosuppressive when tested on human and murine lymphocytes in a variety of in vitro immune assays, as it is also on syngenic (ovine) lymphocytes.

Methods: In the present paper, we first verified that this property to act across species also occurred in vivo assays; r.oTP was able to down regulate a local GVH reaction assay (PLN assay) in mice. We then took advantage of these properties of r.oTP to investigate its in vivo effects during murine pregnancy as there is no ovine equivalent of the murine CBA/J x DBA/2 resorption prone mating combination.

Results: When given in the postimplantation period, r.oTP drastically boosted resorptions in the CBA/J x DBA/2 matings, as did murine recombinant gamma interferon. However, the same r.oTP treatment in the peri-implantation period resulted in a reduction in resorptions in this spontaneous abortion system.

Conclusion: The data suggested that r.oTP might have acted more by favouring implantation and embryo survival than by preventing the resorption process itself. The mechanisms possibly underlying these effects, as well as the putative uses of r.oTP evolving from these data, are discussed.