TLR4 and infection: Indeed, all the genes upregulated in the previous infection did not change their expression in this system, while we observed upregulation of caspase-9 (CASP9), Toll-like receptor 3 (TLR3) and Toll-like receptor 4 (TLR4) mRNAs, and a downregulation of IL1B mRNA after exposure to WN stool sample compared to the same cells exposed to WT stool sample.