TLR2 in æ T cells is required for metabolic support of their IL-17A response to a commensal bacterium on the ocular surface

Abstract The ocular surface is colonized by commensal microbiota, which tune the local mucosal immune response. We previously identified an ocular surface commensal, Corynebacterium mastitidis (C. mast), which induced IL-17A production from γδ T cells in the conjunctiva and eye-draining lymph nodes (DLN), and enhanced host resistance to fungal and bacterial pathogens. To elucidate how IL-17A producing γδ T cells (γδT17) are activated by C. mast, we associated WT and TLR2−/− mice with C. mast, and investigated the role of TLR2 in this process. This was based on the rationale that C. mastis a Gram-positive bacterium and that TLR2 expression on γδT cells increased after C. mast association. Mechanistic studies showed that TLR2 expression was required not only on DCs (for IL-1 production) but also on the γδT cells. RNA-Seq revealed that genes related to mitochondrial oxidative phosphorylation were dysregulated in TLR2−/− γδT17 cells, indicating that engagement of TLR2 may regulate metabolic processes in γδT17 cells. Seahorse assay confirmed that TLR2−/− γδ T17 cells displayed impaired oxygen consumption rates and lower ATP production. Interestingly, lysosomal activity, which plays a central role in cellular metabolism, was decreased in TLR2−/− γδ T17 cells. Enhancement of lysosomal activity by curcumin C1 restored ATP generation in TLR2−/− γδ T17 cells. We propose that intrinsic TLR2 signaling in γδ T cells is required for metabolic support of their IL-17A response.