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. (shrink)

Uteroferrin, a purple‐colored, iron‐containing acid phosphatase, with many of the properties of a lysosomal hydrolase, transports iron from the mother to the conceptus in pregnant pigs. Uteroferrin, however, is but one member of what may be a broad class of iron‐containing phosphatases with unusual spectral properties which result from a novel type of di‐iron active site. The biological function of uteroferrin is unknown. We argue here that the in vivo function of uteroferrin, despite its undoubted ability to act as a (...) potent acid phosphatase, is that of a transplacental iron transporter. (shrink)