Interferon-tau Polymorphisms and Their Potential Functions in Ruminants

In ruminants, the establishment and maintenance of pregnancy requires production of a Type I interferon, termed IFN-. This protein is synthesized by the developing conceptus and interacts with the uterus to promote continued secretion of progesterone. Multiple genes encode IFN-, and a majority of these genes are transcribed during early pregnancy. The proteins possess divergent biological activities, including the ability to prevent the corpus luteum from regressing at the end of a normal estrous cycle. In all likelihood multiple IFN- isoforms are produced during early pregnancy to ensure that sufficient quantities of bioactive IFN- are present to modulate uterine biology during early pregnancy. Although IFN- has evolved to serve as the pregnancy recognition hormone in ruminants, other Type I IFNs, such as IFN- and IFN-, are capable of producing a uterine response similar to that of IFN-. Hence, the polymorphic nature of IFN- genes appear to have generated new and potentially more active forms of the hormone, but the unique expression pattern for IFN- is likely the preeminent feature ensuring its use as the maternal recognition of pregnancy factor in ruminants.