Expression analysis of TLR signaling pathway genes under lipopolysaccharide-induced and F17-infected sheep intestinal epithelial cells.

() F17 is one of the main pathogens causing diarrhea in young livestock. The specific F17 fimbriae and lipopolysaccharide (LPS) in the surface components of F17 induces immune activation interacting with the intestinal epithelial cells (IECs)-expressed innate immune toll-like receptors (TLRs) signaling pathway. In this study, the expression patterns of eight canonical genes from the TLR signaling pathway (, , , , , , and ) were analyzed in LPS-induced IECs, F17-infected IECs and ileum tissue of F17-infected lambs. The results showed that increased expression levels of all the studied genes were observed following post-LPS-induced and F17-infected treatment, with having the highest up-regulated expression multiple (compared to NC, fold change = 17.94 and 20.11, respectively), and having the lowest up-regulated expression multiple (fold change = 2.68 and 1.59, respectively), and higher expression levels of all the studied TLR signaling pathway genes were observed in ileum tissue of F17 antagonistic (AN) lambs than in F17 sensitive (SE) lambs. Furthermore, when compared to LPS-induced IECs, F17-infected IECs showed a more pronounced increase in the expression of , and , indicating the different roles of these genes in the IECs resistance to F17 infection. Our results demonstrate that the TLR signaling pathway likely promotes immune activation and provide the first evidence that TLRs have a significant potential to protect against F17 infections.