Data_Sheet_1_Commensal Bacteria-Dependent CD8αβ+ T Cells in the Intestinal Epithelium Produce Antimicrobial Peptides.PDF

<p>The epithelium of the intestine functions as the primary “frontline” physical barrier for protection from enteric microbiota. Intraepithelial lymphocytes (IELs) distributed along the intestinal epithelium are predominantly CD8<sup>+</sup> T cells, among which CD8αβ<sup>+</sup> IELs are a large population. In this investigation, the proportion and absolute number of CD8αβ<sup>+</sup> IELs decreased significantly in antibiotic-treated and germ-free mice. Moreover, the number of CD8αβ<sup>+</sup> IELs was correlated closely with the load of commensal microbes, and induced by specific members of commensal bacteria. Microarray analysis revealed that CD8αβ<sup>+</sup> IELs expressed a series of genes encoding potent antimicrobial peptides (AMPs), whereas CD8αβ<sup>+</sup> splenocytes did not. The antimicrobial activity of CD8αβ<sup>+</sup> IELs was confirmed by an antimicrobial-activity assay. In conclusion, microbicidal CD8αβ<sup>+</sup> IELs are regulated by commensal bacteria which, in turn, secrete AMPs that have a vital role in maintaining the homeostasis of the small intestine.</p>