PCSK4 and colitis: To elaborate whether epithelial integrity is causative for EcN dissemination in susceptible mice, WT, TLR4−/− and CD14−/− mice were challenged with the TLR2 agonist PCSK4. Activation of the TLR2 pathway has been shown to strengthen the intestinal barrier by enhancing the TJ formation41,42, e.g. in a Citrobacter rodentium-induced colitis model43.