In a previous work, we reported that low or high concentrations of LPS induce differential DC activation and maturation resulting in differential T-cell activation and polarization.48 Here we show that the expression of activation CHIR-99021 ic50 and maturation markers of lp DC significantly differs in Endohi and EndoloRag1−/− mice, in E coliMUT or E coliWT and in LPSWT or LPSMUT challenged mice, respectively, according to our in vitro studies. Consistent with this, we found increased expression of TH1/TH17 cytokines in Endohi-, E coliWT-, and LPSWT-treated Rag1−/− mice, but not in the Endolo-, E coliMUT-, or LPSMUT-challenged Rag1−/− mice. Accordingly, treatment of

mice with E coliMUT resulted in increased expression of FoxP3 and treatment with LPSMUT in a reduced expression of IL-17a in the colonic lp T cells. The delivery of purified LPS or LPS by viable bacteria might result in different LPS availability at different intestinal and cellular components,49 and can contribute to the differences in the IL-17a and FoxP3 expression on treatment with LPS or viable bacteria. However, we cannot rule out that an additional factor of viable E coli might account for this effect. Currently,

it seems to be highly likely that the intestinal microbiota plays a critical role in the accumulation and functional maturation of intestinal regulatory T cells.50 We demonstrated that commensal bacterial species, depending on the structure of LPS, can induce or prevent expansion and polarization of intestinal T cells. However, as discussed by Chung et al,33 many questions remain about the causes of differential T-cell response. Fulvestrant chemical structure The different maturation states of lp DC might be induced directly by the commensal bacteria or be due to a secondary effect induced by differences in the local chemokine and cytokine milieu, possibly resulting in

a difference in the downstream T-cell proliferation. Both the administration of bacteria (E coliWT and E coliMUT) and treatment with LPSWT or LPSMUT resulted in alterations in the composition of the intestinal microbiota. Analysis of the intestinal microbiota by deep sequencing techniques implies that phylogenetic groups of bacteria like Firmucutes or Verrucomicrobia might also be involved in the regulation of the intestinal until immune homeostasis. However, additional functional studies need to clarify the biologic relevance of this finding and whether the shift of the intestinal microbiota by LPS administration is a direct effect, or represents a secondary effect due to changes in the local environment in terms of, for example, nutrition, altered cytokine and chemokine patterns, or induction of defensins. In addition, an influence of the altered intestinal microbiota, and therefore the modified endotoxicity of the intestinal microbiota on the maintenance of intestinal homeostasis or induction of inflammation, would be conceivable.