Extracellular Traps Released By Antimicrobial T(H)17 Cells Contribute To Host Defense

T(H)17 cell subpopulations have been defined that contribute to inflammation and homeostasis, yet the characteristics of T(H)17 cells that contribute to host defense against infection are not clear. To elucidate the antimicrobial machinery of the T(H)17 subset, we studied the response to Cutibacterium acnes, a skin commensal that is resistant to IL-26, the only known T(H)17-secreted protein with direct antimicrobial activity. We generated C. acnes-specific antimicrobial T(H)17 clones ((AM)T(H)17) with varying antimicrobial activity against C. acnes, which we correlated by RNA sequencing to the expression of transcripts encoding proteins that contribute to antimicrobial activity. Additionally, we validated that (AM)T(H)17-mediated killing of C. acnes and bacterial pathogens was dependent on the secretion of granulysin, granzyme B, perforin, and histone H2B. We found that (AM)T(H)17 cells can release fibrous structures composed of DNA decorated with histone H2B that entangle C. acnes that we call T cell extracellular traps (TETs). Within acne lesions, H2B and IL-17 colocalized in CD4(+) T cells, in proximity to TETs in the extracellular space composed of DNA decorated with H2B. This study identifies a functionally distinct subpopulation of TH17 cells with an ability to form TETs containing secreted antimicrobial proteins that capture and kill bacteria.