TLR5 and colitis: In mice that exhibit spontaneous development of colitis, such as those lacking Toll-like receptors-5 (Tlr5−/−), IL-10 (Il-10−/−) or the transcription factor T-bet and the recombinase activating gene Rag (T-bet−/− x Rag2−/−), an increased intestinal level of Proteobacteria was reported [251–255].