Microbiota-activated CD103+ DCs stemming from microbiota adaptation specifically drive γδT17 proliferation and activation

Abstract

BackgroundIL-17-producing γδT cells (γδT17) promote autoinflammatory diseases and cancers. Yet, γδT17 peripheral regulation has not been thoroughly explored especially in the context of microbiota-host interaction. The potent antigen-presenting CD103+ dendritic cell (DC) is a key immune player in close contact with both γδT17 cells and microbiota. This study presents a novel cellular network among microbiota, CD103+ DCs, and γδT17 cells.MethodsImmunophenotyping of IL-17r−/− mice and IL-17r−/− IRF8−/− mice were performed by ex vivo immunostaining and flow cytometric analysis. We observed striking microbiome differences in the oral cavity and gut of IL-17r−/− mice by sequencing 16S rRNA gene (v1–v3 region) and analyzed using QIIME 1.9.0 software platform. Principal coordinate analysis of unweighted UniFrac distance matrix showed differential clustering for WT and IL-17r−/− mice.ResultsWe found drastic homeostatic expansion of γδT17 in all major tissues, most prominently in cervical lymph nodes (cLNs) with monoclonal expansion of Vγ6 γδT17 in IL-17r−/− mice. Ki-67 staining and in vitro CFSE assays showed cellular proliferation due to cell-to-cell contact stimulation with microbiota-activated CD103+ DCs. A newly developed double knockout mice model for IL-17r and CD103+ DCs (IL-17r−/−IRF8−/−) showed a specific reduction in Vγ6 γδT17. Vγ6 γδT17 expansion is inhibited in germ-free mice and antibiotic-treated specific pathogen-free (SPF) mice. Microbiota transfer using cohousing of IL-17r−/− mice with wildtype mice induces γδT17 expansion in the wildtype mice with increased activated CD103+ DCs in cLNs. However, microbiota transfer using fecal transplant through oral gavage to bypass the oral cavity showed no difference in colon or systemic γδT17 expansion.ConclusionsThese findings reveal for the first time that γδT17 cells are regulated by microbiota dysbiosis through cell-to-cell contact with activated CD103+ DCs leading to drastic systemic, monoclonal expansion. Microbiota dysbiosis, as indicated by drastic bacterial population changes at the phylum and genus levels especially in the oral cavity, was discovered in mice lacking IL-17r. This network could be very important in regulating both microbiota and immune players. This critical regulatory pathway for γδT17 could play a major role in IL-17-driven inflammatory diseases and needs further investigation to determine specific targets for future therapeutic intervention.Electronic supplementary materialThe online version of this article (doi:10.1186/s40168-017-0263-9) contains supplementary material, which is available to authorized users.

Mutual interplay between IL-17–producing γδT cells and microbiota orchestrates oral mucosal homeostasis

“…Thus, the gingiva represents a unique site in which homeostatic development of intraepithelial γδT cells is clearly modulated by the microbiota. This is in line with a study reporting reduced levels of IL-17-producing γδT cells in the cervical lymph nodes of GF mice, by a mechanism involving cellto-cell contact between γδT cells and CD103 + dendritic cells (37). Interestingly, we demonstrated previously that CD103 is also expressed by a subset of mucosal LCs, a special type of dendritic cell located in the gingival epithelium (9).…”

“…We similarly revealed a decrease in gingival γδT cells, which was attributed to a significant reduction of the Vγ6 + subset. This is in agreement with a recent study reporting that oral microbiota expanded IL-17-producing Vγ6 + cells systemically (37). Unfortunately, Krishnan et al did not examine the Vγ6 + cells in GF mice and, moreover, they limited their analysis to the first week after birth, which might cloak the large impact of the microbiota on Vγ6 + cells.…”

IL ‐7‐dependent compositional changes within the γδ T cell pool in lymph nodes during ageing lead to an unbalanced anti‐tumour response

“…In old mice, the preference amongst Vd5 and Vd4 segments was reversed compared with young mice: Vd4 (~60%) was preferentially used followed by Vd5 (~30%; Fig 4B, lower-left panel). As reported, invariant Vc6 + T cells from young and old mice used only the Vd1 segment for the assembly of their cd TCR [44,49,50]…”

γδ T Cells: Unexpected Regulators of Cancer Development and Progression

“…We have already begun to see the effects that microbiota play on driving γδ T-dependent tumor development and progression in both murine models and patients. The host-microbiota interaction and how this regulates γδ T cells will provide much needed additional answers as to how γδ T cells are regulated during health (55) to then better understand how to restore proper functioning in disease. Understanding γδ T cell homeostatic regulation will provide information needed to prevent cancer development.…”