Differences in Lymphocyte-Regulatory Activity Among Variants of Ovine IFN-τ

Abstract

Interferon-τ (IFN-τ) is secreted from trophectoderm of the ruminant preimplantation conceptus and functions during pregnancy to prevent luteolysis. In addition, IFN-τ can inhibit proliferation of peripheral blood lymphocytes (PBL) and other cells. Several distinct ovine IFN-τ (OvIFN-τ) gene variants exist; three of these (IFN-τ4, IFN-τ6d, IFN-τ11) differ in their ability to prevent luetolysis (IFN-τ4 > IFN-τ6d > IFN-τ11), inhibit growth of Daudi cells (IFN-τ4 > IFN-τ6d > IFN-τ11), and induce an antiviral state (IFN-τ4 > IFN-τ6d= IFN-τ11). The present objective was to compare variants for differences in ability to inhibit proliferation of phytohemagglutinin-stimulated PBL. At equal concentrations, IFN-τ4 was more inhibitory than IFN-τ6d, IFN-τ11, or an IFN-ω control. Similar differences in potency were seen when IFN-τ variants were tested at equal antiviral concentrations. Thus, the sheep trophectoderm secretes variants of IFN-τ that differ in ability to regulate lymphocyte function. The nature of the effect of the trophectoderm on endometrial lymphocytes may depend on the relative amount of each variant produced.