Recent developments and potentialities for reducing embryo mortality in ruminants: the role of IFN-<font face="symbol">t</font> and other cytokines in early pregnancy

Abstract

This review considers the potential reduction of embryo mortalityin vitro and in vivo in ruminants.Data on cytokines provided by different fields of reproductive immunology andbiology were collated. Because of the crucial importance of the localinteractions between the embryo and its dam, the expression of growth-factorand cytokine genes was analysed in the embryo proper, trophoblast, oviduct andendometrium by reverse transcriptase polymerase chain reaction in sheep and incattle during the pre- and periimplantation periods. Many deleteriouscytokines, such as tumour necrosis factor-&alpha;, intereron-&gamma; (IFN-&gamma;), interleukin-2 (IL-2), and beneficial cytokines, such as transforming growthfactor-&beta;, leukaemia inhibiting factor, colony-stimulating factor-1(CSF-1), ganulocyte-macrophage CSF, IL-1, IL-3, IL-4, IL-6, IL-10 andIFN-&gamma; appeared to be involved in embryo survival in ruminants and otherspecies. Their administration is efficient in a murine experimental model(CBA/J DBA/2) of embryonic and fetal mortality. For instance,recombinant ovine IFN-&tgr; (roIFN-&tgr; ) injected at the moment ofimplantation drastically reduces embryonic mortality in this model. Inruminants, roIFN-&tgr; and recombinant bovine IFN-&tgr; are very efficient inmaintaining progesterone luteal secretion in cyclic animals. The involvementof IFN-&tgr; in the mechanisms of maternal pregnancy recognition areparticularly detailed in relation to inbition of 13,14dihydro-15-keto-prostaglandin F<emph type="8">2&alpha; (PGFM) pulsesand oxytocin uterine receptivity. A synthetic model of the anti-luteolyticeffects of IFN-&tgr; on the endometrial cell is proposed. Finally, theparticular potential of serum pregnancy-specific proteins (PSPs: PSPB, PSP60,pregnancy-associated glycoprotein) for monitoring embryo survival, withexamples given for cattle and sheep is underlined.