Lipopolysaccharide (LPS) plays an important role in the activation of innate immune cells, leading to secretion of proinflammatory factors and bridging the adaptive immune system. Exposing total mouse thymic cells culture to LPS induced a unique expression profile of cytokines (IL-17A, IL-17F, and IL-22) and the essential ROR-γt master transcription factor, which suggested a preferential differentiation of thymocytes towards the Th17 cell phenotype. Th17-polarizing molecules (IL-23, IL-23R, IL-6, and TGF-β) and IL-17A(+)CD4(+) thymocytes were also specifically produced by the in vitro LPS-stimulation of thymic cells. Furthermore, both the expression of Th17 differentiation-related molecules and the frequency of Th17 cells were significantly up-regulated with increasing doses of LPS, as evidenced by quantitative RT-PCR and flow cytometric analysis, respectively. The expressions and frequency reached maximum levels when LPS exposure had been maintained at an extremely high concentration (100 μg/mL) for 48 h. On the other hand, depletion of thymic dendritic cells (DCs) blocked the LPS-induced polarization of thymus-derived Th17 cell lineage. Addition of bone marrow-derived DCs (BMDCs) to the purified immature CD4(+) CD62L(low) thymocytes culture recovered the switch towards Th17 cells, which synergistically prompted the cytotoxic activity of CD8(+) T cells. Taken together, our data indicates that high doses of LPS can promote the differentiation of mouse thymus-derived Th17 cells by a mechanism involving components associated with mature DCs.

BACKGROUND/AIMS Mucosa-associated T-lymphocyte (MAIT) cells that are selectively accumulated in the intestinal mucosa may be involved in immune regulation. MAIT cells are determined by their Vα7.2-Jα33 (human)/Vα19-Jα33 (mice) invariant chain. The encoding DNA sequences of Human Jα33 and mouse Jα33 are identical. In order to study the role of MAIT cells in IBD we produced anti-Jα33 antibody to detect MAIT cells in TNBS induced IBD models. METHODOLOGY Colitis was induced by TNBS in male BALB/c mice. Jα33+MAIT cells from normal mice were transferred into TNBS induced mice as donors. Colitis severity was evaluated clinically and histologically, under the condition of transferred Jα33+MAIT cells. RESULTS The mRNA and protein expression levels of MAIT aTCR in the colonic mucosa were decreased after TNBS administration; Jα33+MAIT cells were aggregated in spleen after TNBS administration. The disease activity index (DAI) which was determined by weight loss, stool consistency and intestinal bleeding, increased after TNBS administration. Transferred Jα33+MAIT cells significantly degrade the increase in the disease activity index scores. CONCLUSIONS Taken together, the results indicated that the aggregation of Jα33+MAIT cells in intestinal mucosa improved TNBS-induced colitis. We conclude that Jα33+MAIT cells play a protective role in TNBS induced intestinal inflammation.