TLR2 and colitis: Moreover, E. coli strain Nissle 1917 has been shown to ameliorate DSS colitis in C57BL/6 WT mice, but not in mice deficient in TLR2 or TLR4, suggesting that activation of both TLR2 and TLR4 signaling is pivotal for this microorganism in order to exert its beneficial effects (139).