TLR9 and colitis: For example, experimental studies in hosts knockout for TLR9, TLR4, and TLR2 have shown increased susceptibility to the development of a colitis induced by dextran sodium sulfate (DSS) [12, 13], as well as the protective role against DSS colitis induced by agonists of TLR2 and TLR4 supplement [12, 13].