Effect of interleukin-3 on ovine trophoblast interferon during early conceptus development

The effect of interleukin-3 (IL-3) on conceptus production of ovine interferon tau (olFNτ) was examined using two dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis (2D SDS-PAGE), western blot, northern/slot blot,in situ hybridization and immunohistochemical methodologies. Ovine conceptuses (day 17,n=14) were culturedin vitro for 24 h in Eagle's Minimum Essential Medium (MEM) containing various doses of human recombinant interleukin-3 (hIL-3). At 75 and 150 colony forming units (units)/ml hIL-3, amounts of oIFNτ released into the culture media increased 3-8-fold over controls while at 300 units/ml (60 pM), hIL-3 did not enhance oIFNτ production. These variations in production of oIFNτ parallel amounts of oIFNτ mRNA detected by northern and slot blot analyses. Ovine IL-3 mRNA was primarily localized at luminal and glandular epithelia with minor staining at stromal regions of uterine endometria collected from day 17 pregnant ewes but its polypeptide was localized in the luminal epithelial region. However, such signals were not detected in day 17 conceptuses. Ovine IL-3 mRNA and its polypeptide were also localized at the same regions of the endometrium obtained from cyclic ewes on days 8 and 12. The effect of hIL-3 on the enhancement of oIFNτ productionin vitro could be mimicked by the addition of phorbol 12-myristate 13-acetate (PMA). The present observations demonstrate that the hemopoietic cytokine, IL-3, stimulates conceptus production of oIFNτin vitro and that ovine IL-3 and its mRNA are localized in the maternal endometrium. These results suggest that a cytokine, IL-3, produced by the maternal endometrium, is involved in conceptus production of oIFNτ which may result from the activation of a second messenger system, protein kinase C.