Interferon tau

Thirty years ago, a novel type I interferon (IFN) was identified by molecular cloning of cDNA libraries prepared from RNA of sheep and bovine preimplantation embryos. This protein was eventually named IFN-tau (IFNT) to emphasize its trophoblast-dependent expression. The function of IFNT is not immunologically dependent. Instead, it interacts with the maternal system to initiate and maintain pregnancy. This activity is essential for the maintenance of pregnancy (Ealy AD et al. 2017). The discovery of this signaling molecule as an IFN-like sequence was surprising for the scientific community in the field of reproduction, since a homologous molecule in humans has antiviral and antiproliferative activity and is frequently used in human medicine (Imakawa K et al. 2017). Indeed, the oTP-1 cDNA has a high degree of similarity to IFNα cDNAs (55-65%), but is most similar to IFN-omega (IFNω) cDNA (85%) (Imakawa et al. 1987). Four cysteine residues present in IFNα, IFNβ and IFNω are fully conserved in oTP-1 and bTP-1 cDNAs (Imakawa K et al. 2017).

Interferon tau (IFN-τ) is a cytokine from the type I interferon family (see interferons below), which is mainly produced by the developing embryo in ruminants such as cows and sheep. It plays a crucial role in early pregnancy by influencing the maternal immune response and promoting the development of pregnancy.

Role in pregnancy: IFN-τ is essential for the maintenance of pregnancy in ruminants. It is secreted by the trophoblast cells of the developing embryo and helps to prevent the breakdown of the corpus luteum, which is essential for the production of progesterone - a hormone necessary for the maintenance of pregnancy (Ealy AD et al. 2017; Hansen TR et al. 2017).

Mechanism of action: IFN-τ acts on the lining of the uterus (endometrium) to induce a series of changes that create an immunotolerant environment in which the embryo can develop without being rejected by the maternal immune system. It also modulates the expression of various genes involved in immune regulation and uterine susceptibility.

Immunomodulatory effects: Beyond its role in pregnancy, IFN-τ has immunomodulatory properties. It can influence the activity of various immune cells, including macrophages and T cells. This helps to create a favorable environment for the developing embryo and protect it from possible immune reactions.

Animal health and reproduction: Measurement of IFN-τ levels has been explored as a potential biomarker for the early detection of pregnancy in cattle and other ruminants. This has implications for reproductive management in livestock as it can help farmers and veterinarians to better understand and manage fertility problems.

Research applications: IFN-τ is also of interest for research in the fields of reproductive biology, immunology and potential therapeutic applications in veterinary and human medicine. Its unique properties may offer insights into immune tolerance and the maintenance of pregnancy. Ovine TP-1 was originally discovered as a secretory product of ovine receptors that rescues the maternal corpus luteum (CL), and indeed uterine infusion of oTP-1 prolonged interoestrus intervals.

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