title: Nature and possible functions of interferons secreted by the preimplantation pig blastocyst.
abstract: In several ungulate species, the preimplantation trophoblast, among various secretions, produces large amounts of antiviral activity that was identified as interferon (IFN). IFNs (types I and II) are pleiotropic cytokines, which in addition to a potent antiviral activity, exert multiple effects on cell growth and differentiation, in particular on the cells of the immune system. In ruminants, trophoblastic IFN, or trophoblast protein-1 (TP-1), was found to consist of a multigenic family related to type I IFN-omega. These IFNs exert hormone-like effects through receptors present on the endometrium, leading to the prolongation of luteal life-span and hence to sustained progesterone secretion. In pigs, a species in which the maternal recognition of pregnancy is controlled by conceptus-derived oestrogens, two IFNs have been found in the preimplantation trophoblast. The major species is IFN-gamma (type II), that so far had been found only in activated T lymphocytes and natural killer (NK) cells. Transcription of the IFN-gamma gene in the pig trophoblast differs from that in mature lymphocytes, since two mRNAs are present. The other component with antiviral activity is a novel type I IFN, distant in sequence from IFN-alpha, beta, omega, and containing seven cysteines in its deduced mature protein. These two unrelated IFNs are temporally co-induced, with maximal secretion at day 16 of pregnancy. Specific receptors for both IFNs have been found on endometrial epithelial cells, but not on the preimplantation trophoblast, suggesting a paracrine effect on the uterus. Different hypotheses as to their role(s) in the establishment or maintenance of implantation are discussed. Whereas an indirect anti-infectious (antiviral) protection of the conceptus by IFNs cannot be ruled out, arguments are presented that do not favour a role in the immune tolerance of the conceptus.
authors.affiliation: Unité de Virologie et d'Immunologie Moléculaires, INRA, Jouy en Josas, France.
authors.forename: C
authors.initials: C
authors.lastname: La Bonnardière
mesh_terms: D000818:Animals; D001755:Blastocyst / Q000502:physiology*; D010064:Embryo Implantation / Q000502:physiology*; D005260:Female; D007370:Interferon Type I / Q000378:metabolism; D007371:Interferon-gamma / Q000378:metabolism; D007372:Interferons / Q000378:metabolism*; D011247:Pregnancy; D013552:Swine / Q000502:physiology*
chemical_list: D007370:Interferon Type I; D007371:Interferon-gamma; D007372:Interferons