The histone demethylase Kdm6b regulates the maturation and cytotoxicity of TCR alpha beta(+)CD8 alpha alpha(+) intestinal intraepithelial lymphocytes

Intestinal intraepithelial lymphocytes (IELs) are distributed along the length of the intestine and are considered the frontline of immune surveillance. The precise molecular mechanisms, especially epigenetic regulation, of their development and function are poorly understood. The trimethylation of histone 3 at lysine 27 (H3K27Me3) is a kind of histone modifications and associated with gene repression. Kdm6b is an epigenetic enzyme responsible for the demethylation of H3K27Me3 and thus promotes gene expression. Here we identified Kdm6b as an important intracellular regulator of small intestinal IELs. Mice genetically deficient for Kdm6b showed greatly reduced numbers of TCR alpha beta(+)CD8 alpha alpha(+) IELs. In the absence of Kdm6b, TCR alpha beta(+)CD8 alpha alpha(+) IELs exhibited increased apoptosis, disturbed maturation and a compromised capability to lyse target cells. Both IL-15 and Kdm6b-mediated demethylation of histone 3 at lysine 27 are responsible for the maturation of TCR alpha beta(+)CD8 alpha alpha(+) IELs through upregulating the expression of Gzmb and Fasl. In addition, Kdm6b also regulates the expression of the gut-homing molecule CCR9 by controlling H3K27Me3 level at its promoter. However, Kdm6b is dispensable for the reactivity of thymic precursors of TCR alpha beta(+)CD8 alpha alpha(+) IELs (IELPs) to IL-15 and TGF-beta. In conclusion, we showed that Kdm6b plays critical roles in the maturation and cytotoxic function of small intestinal TCR alpha beta(+)CD8 alpha alpha(+) IELs.