Immunity https://doi.org/10.1016/j.immuni.2019.05.004 (2019)
The TH17 subset of helper T cells is pathogenic in a variety of inflammatory disorders but also has tissue-resident homeostatic roles in the intestine. In Immunity, Omenetti et al. compare the characteristics of TH17 cells induced by commensal microbiota, notably segmented filamentous bacteria (SFB), and those elicited by a pathogen (Citrobacter rodentium). Secretion of the cytokine IL-17A is higher in SFB-induced TH17 cells, the cytokine IFN-γ is more abundant in C. rodentium–elicited TH17 cells, and both groups of cells produce IL-22. SFB-induced TH17 cells do not expand in response to infection with C. rodentium. RNA-sequencing analysis indicates enrichment for transcripts encoding molecules involved in anti-inflammatory pathways and oxidative phosphorylation in SFB-induced TH17 cells and enrichment for markers of glycolysis, biosynthesis and pro-inflammatory pathways in C. rodentium–elicited TH17 cells. These results indicate that two functionally distinct populations of TH17 cells can reside in the gut simultaneously during pathogen-induced inflammation.