Trophoblast IFN-τ Differentially Induces Lymphopenia and Neutropenia in Lambs

Abstract

Type I interferons (IFN), including IFN-α and IFN-β, cause severe lymphopenia, resulting from altered lymphocyte recirculation and redistribution. IFN-τ, a product of trophectoderm of ruminant conceptuses and new member of the type I IFN family has not been examined for its effect on leukocyte recirculation. Additionally, differential effects of type I IFNs on the redistribution and recirculation of subsets of T cells have not been reported. The present study determined the effects of IFN-τ on the redistribution and recirculation of ovine leukocytes and T cell subsets. Total peripheral blood leukocytes, lymphocytes, and segmented neutrophils were reduced (p < 0.05) following treatment of lambs with IFN-τ. Furthermore, administration of IFN-τ caused an acute, differential reduction in peripheral blood CD4⁺ T cells (p < 0.05), CD5⁺ cells (p < 0.05), and γδ TCR⁺ (p < 0.01) T cells but had no effect on CD8⁺ T cells (p > 0.05). IFN-τ reduced the percentage of γδ T cells by 8-fold and that of CD4⁺ T cells and CD5⁺ cells by <2-fold in peripheral blood when compared with control lambs. The reduction in leukocytes, lymphocytes, and neutrophils was observed as early as 6–12 h after administration of IFN-τ, but levels returned to control values within 48 h. These results indicate that IFN-τ, like other members of the type I IFN family, can have immediate effects on leukocyte recirculation and redistribution. The present study is the first to demonstrate that IFN-τ differentially regulates T cell recirculation with the greatest effect on γδ TcR⁺ T cells.