Trophoblast interferon, or interferon-tau (IFN-т), represents a novel Type I IFN whose expression is restricted to the trophectoderm of preimplantation conceptus placenta of ruminant ungulates, such as sheep, cattle, and goats (see for review). At least three distinct ovine IFN-ts are secreted during the period immediately preceding trophectoderm attachment to the uterine lining, i.e., from Day 12 to 16 of pregnancy. IFN-ts act to extend the life span of the corpus luteum (CL) and thereby grant continued uterine exposure to progesterone, which is required in order for pregnancy to be maintained. Administration of IFN-т into the uteri of nonpregnant ewes or cows provides a temporary prolongation of CL life span, which may last from a few days to several weeks, indicating that other factors, whose identities remain unknown, are probably required for pregnancy to proceed to term (144 days in ewes). buy prednisone
The actions of IFN-т are elicited at the level of the uterus through interaction with type I IFN receptors, most likely present on the endometrial epithelium. The mechanism whereby CL regression is delayed by IFN-т is by a diminution in the pulsatile release of prostaglandin F2ct (PGF2J, the primary luteolytic agent in these species, through pathways that are not well understood (see for reviews).