OBJECTIVE: In ruminant species, a unique type I interferon (IFN), Interferon-τ, is exclusively secreted by the blastocyst and is required for successful pregnancy. Although there is no pregnancy-specific IFN in humans, endometrial IFN expression may be stimulated by Toll-like receptor 3 (TLR3) ligation. We have previously demonstrated cyclic expression of human endometrial epithelial TLR3, with highest expression during mid- and late secretory phases, suggesting a possible role of TLR3 in embryo implantation. The aim of this study is to determine the effects of TLR3 ligation on expression of implantation-associated genes. DESIGN: Laboratory study. MATERIALS AND METHODS: RL95-2 endometrial epithelial cell line and primary cultures of mid-secretory endometrial epithelial cells were treated in triplicate with 5μg/ml of TLR3 ligand, polyinosinic-polycytidylic acid (PolyI:C), a negative control (PolydI:dC), or carrier for 2, 8, 16, and 24 hours. Relative changes in mRNA expression were measured using Taqman® real time RT-PCR (ddCT method) normalized to constitutive genes GAPDH and PPIA in RL95-2 and primary cells, respectively. PolyI:C effects in RL95-2 cells are completely dependent on TLR3. RESULTS: The table shows the peak change in mRNA expression for each gene studied. Treatment with negative controls, polydI:dC or carrier had no effects. Gene names follow standard HUGO nomenclature with common abbreviations noted. Although LIF and CD55 were not induced in primary cells, baseline expression of each was very high in control cells. Also, IP-10 (CXCL10) induction has been shown previously in response to polyI:C. CONCLUSIONS: TLR3 ligation, known to mediate inflammatory responses to viral products, may also be important in promoting embryo implantation, via induction of IDO, COX-2, RANTES, and IP-10. Further studies are ongoing to investigate the role of TLR3 in embryo implantation. Additionally, this is the first evidence of IFNε expression by human endometrium.Table 1Changes in Gene Expression with TLR3 LigationPeak Increase in Expression (fold change; hours)GeneFunctionRL95-2 CellsPrimary CellsINDO (IDO)Fetal Immunotolerance78x; 8h9x; 8hPTGS2 (COX2)Implantation defect in KO Mice6x; 8h10x; 2hCCL5 (RANTES)Embryo Invasion1900x; 24h86x; 8hLIFEmbryo Attachment50x; 8hNo ChangeCD55 (DAF)Prevents Complement Attack4x; 2hNo ChangeISG15Induced at Implantation Sites23x; 8h7x; 8hIFNB1 (IFNβ)Unknown3700x; 2h120x; 2hIFNE1 (IFNε)UnknownNo ChangeNo Change Open table in a new tab