Localization of intestinal intraepithelial T lymphocytes involves regulation of αEβ7 expression by transforming growth factor‐β

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Abstract
Induction of αEβ7 expression on T cells by transforming growth factor (TGF)‐β is thought to be important for intestinal intraepithelial T lymphocyte (IEL) entry into the epithelial compartment. However, there has been no in vivo evidence that up‐regulation of αEβ7 expression on T cells by TGF‐β is critical for the selective localization of intestinal IEL in the epithelial area. We have recently established transgenic mice expressing Smad7 under the control of a distal lck promoter where TGF‐β/Smad signaling is specifically blocked in mature T cells. Here we showed that TGF‐β‐mediated up‐regulation of αEβ7 was impaired on T cells isolated from the Smad7 transgenic mice associated with reduced numbers of intestinal IEL when compared with that in wild‐type littermates. These results indicated that failure to induce αEβ7 on T cells by TGF‐β resulted in reduced numbers of intestinal IEL, suggesting the importance of αEβ7 expression by TGF‐β in selective localization of intestinal IEL.