Abstract

In order to survive, the developing conceptus must interrupt the normal ovarian cycle of the mother and extend the production of progesterone by the corpus luteum. An unusual Type 1 interferon (IFN), related structurally to the IFN–α molecule and produced in massive amounts for only a few days by the first epithelium (trophectoderm) of the preimplantation conceptus, has been implicated as the antiluteolytic agent in sheep and cattle. IFN‐a therapy during this critical period can also improve pregnancy success in sheep. It remains unclear, however, whether the trophoblast IFN have specialized biological properties or whether they are unique merely in the timing, magnitude and site of their expression.