RECENT DEVELOPMENTS AND POTENTIALITIES FOR REDUCING EMBRYO MORTALITY IN RUMINANTS - THE ROLE OF IFN-TAU AND OTHER CYTOKINES IN EARLY-PREGNANCY

This review considers the potential reduction of embryo mortality in v itro and in vivo in ruminants. Data on cytokines provided by different fields of reproductive immunology and biology were collated. Because of the crucial importance of the local interactions between the embryo and its dam, the expression of growth-factor and cytokine genes was a nalysed in the embryo proper, trophoblast, oviduct and endometrium by reverse transcriptase polymerase chain reaction in sheep and in cattle during the pre- and periimplantation periods. Many deleterious cytoki nes, such as tumour necrosis factor-alpha, intereron-gamma (IFN-gamma) , interleukin-2 (IL-2), and beneficial cytokines, such as transforming growth factor-beta, leukaemia inhibiting factor, colony-stimulating f actor-1 (CSF-1), ganulocyte-macrophage CSE IL-1 IL-3, IL-4, IL-6, IL-1 0 and IFN-tau appeared to be involved in embryo survival in ruminants and other species. Their administration is efficient in a murine exper imental model (CBA/JxDBA/2) of embryonic and fetal mortality. For inst ance, recombinant ovine IFN-tau (roIFN-tau) injected at the moment of implantation drastically reduces embryonic mortality in this model. In ruminants, roIFN-tau and recombinant bovine IFN-tau are very efficien t in maintaining progesterone luteal secretion in cyclic animals. The involvement of IFN-tau in the mechanisms of maternal pregnancy recogni tion are particularly detailed in relation to inbition of 13,14 dihydr o-15-keto-prostaglandin F-2 alpha, (PGFM) pulses and oxytocin uterine receptivity. A synthetic model of the anti-luteolytic effects of IFN-t au on the endometrial cell is proposed. Finally, the particular potent ial of serum pregnancy-specific proteins (PSPs: PSPB, PSP60, pregnancy -associated glycoprotein) for monitoring embryo survival, with example s given for cattle and sheep is underlined.