Differences in lymphocyte-regulatory activity among variants of ovine IFN-tau

Interferon-tau (IFN-tau) is secreted from trophectoderm of the ruminant pre implantation conceptus and functions during pregnancy to prevent luteolysis . In addition, IFN-tau can inhibit proliferation of peripheral blood lympho cytes (PBL) and other cells. Several distinct ovine IFN-tau (OvIFN-tau) gen e variants exist; three of these (IFN-tau4, IFN-tau 6d, IFN-tau 11) differ in their ability to prevent luetolysis (IFN-tau4 > IFN-tau 6d = IFN-tau 11) , inhibit growth of Daudi cells (IFN-tau4>IFN-tau 6d>IFN-tau 11), and induc e an antiviral state (IFN-tau4>IFN-tau 6d = IFN-tau 11). The present object ive was to compare variants for differences in ability to inhibit prolifera tion of phytohemagglutinin-stimulated PBL. At equal concentrations, IFN-tau 4 was more inhibitory than IFN-tau 6d, IFN-tau 11, or an IFN-omega control. Similar differences in potency were seen when IFN-tau variants were tested at equal antiviral concentrations. Thus, the sheep trophectoderm secretes variants of IFN-tau that differ in ability to regulate lymphocyte function. The nature of the effect of the trophectoderm on endometrial lymphocytes m ay depend on the relative amount of each variant produced.