IL-10 prevents naturally occurring fetal loss in the CBA x DBA/2 mating combination, and local defect in IL-10 production in this abortion-prone combination is corrected by in vivo injection of IFN-tau.

CBA x DBA/2 placentae are quantitatively or qualitatively deficient in their production of the anti-inflammatory Th2-type cytokines IL-4 and IL-10 compared with the nonresorption-prone CBA x BALB/c mating combination. Wastage in this mating combination is accompanied by increased levels of local inflammatory cytokines. In addition, alloimmunization enhances the placental production of IL-4 and IL-10 in CBA x DBA/2 matings. Furthermore, rIL-10 by itself completely reverses the high incidence of fetal resorption after i.p. injection. Conversely, anti-IL-10 increases the resorption rate, but only in CBA x DBA/2 matings. On the other hand, injecting either anti-IFN-gamma or pentoxifillin (an anti-TNF agent) partially reduces the resorption. When given together, they produce a synergistic remission of fetal loss. Finally, we report that recombinant ovine trophoblast protein, an IFN-tau which is known to influence reproductive outcome in ruminants, can also counteract increased CBA x DBA/2 fetal resorption. It simultaneously induces increased placental IL-4 and IL-10 production in this mating combination. These results indicate that the placentally produced anti-inflammatory cytokines can play a vital role in the survival to term of the fetal allograft, by counteracting deleterious inflammatory cytokines.

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.

Recombinant ovine trophoblastin (roTP) inhibits ovine, murine and human lymphocyte proliferation.

Ovine trophoblastic protein (oTP) is a 20-kDa embryonic secretory product constitutively secreted by ovine conceptus trophoblast from days 12-22 of pregnancy. Amino acid sequencing as well as molecular cloning revealed it to bear structural analogies with interferons of the class 2 alpha subfamily, defining the tau interferon group. It is endowed with classical interferon-like biological activities. Recombinant ovine trophoblastin (roTP), produced by genetic engineering, was purified by anion exchange HPLC to a high degree of homogeneity (98%). It behaved in immunodetection and antiviral activity assays like the natural form. We show here that when assayed on PHA-driven murine, human, and ovine (sheep) lymphocyte proliferation, roTP is immunosuppressive. It also inhibits unidirectional and bidirectional murine and human mixed lymphocyte reactions (MLRs). Since natural oTP possesses (at least) 5 isoforms, we also assayed these for immunosuppressive activities. All of them inhibited PHA-driven human and ovine lymphoblastogenesis. Finally, CD4+ and CD8+ ovine T cell selection was performed by panning. In contrast with earlier observations assaying roTP activity on human lymphocytes, both ovine CD4 and CD8 T cell subsets were sensitive to roTP in a PHA-driven proliferation assay. It is therefore suggested that trophoblast interferons might have a strategic function in preventing early embryonic demise by immunologic rejection, at least in ovine species.