Segmented filamentous bacteria (SFB) in the microbiota are sufficient to induce TH17 cells in the lamina propria of the small intestine. In Nature, Yang et al. show that the T cell antigen receptor (TCR) repertoire of intestinal TH17 cells is distinct from that of other intestinal CD4+ T cell subsets and recognizes antigens encoded by SFB. Lamina propria TH17 cells show enrichment for Vβ14+ TCRs, and dominant CDR3 sequences shared by mice show enrichment in either TH17 cells or non-TH17 cells. TCRs cloned from TH17 cells respond to SFB-encoded antigens. Naive T cells from mice with transgenic expression of SFB-specific TCRs migrate to the small intestine and become either TH17 cells in SFB-colonized hosts or TH1 cells if the specific antigen is engineered to be expressed by Listeria monocytogenes. These results indicate that the bacterial context in which cognate antigen is delivered dictates the fate of the antigen-specific T cell.

Nature (13 April 2014) doi:10.1038/nature13279