Interleukin-23-Dependent γ/δ T Cells Produce Interleukin-17 and Accumulate in the Enthesis, Aortic Valve, and Ciliary Body in Mice

Arthritis Rheumatol. 2016 Oct;68(10):2476-86. doi: 10.1002/art.39732.


Objective: The spondyloarthritides (SpA) are a group of rheumatic diseases characterized by ossification and inflammation of entheseal tissue, the region where tendon attaches to bone. Interleukin-23 (IL-23) is involved in the pathogenesis of SpA by acting on IL-23 receptor (IL-23R) expressed on enthesis-resident lymphocytes. Upon IL-23 binding, CD3+CD4-CD8- tissue-resident lymphocytes secrete IL-17A and IL-22, leading to inflammation, bone loss, and ossification. Knowledge about enthesis-resident lymphocytes remains fragmentary, and the contribution of entheseal γ/δ T cells in particular is not clear. This study was undertaken to investigate the presence of γ/δ T cells in the enthesis.

Methods: We used 2-photon microscopy and flow cytometry to analyze entheseal lymphocytes from C57BL/6, Tcrd-H2BeGFP, Rorc-GFP, and IL-23R-eGFP mice. To analyze entheseal γ/δ T cells in IL-23-induced inflammation, Tcrd-H2BeGFP mice were crossed with mice of the susceptible B10.RIII background. Hydrodynamic injection of IL-23 minicircle DNA was performed for overexpression of IL-23 and induction of inflammation. Light-sheet fluorescence microscopy was used to visualize arthritic inflammation.

Results: Activated Vγ6+CD27- γ/δ T cells were abundant in uninflamed entheseal tissue and constituted the large majority of retinoic acid receptor-related orphan nuclear receptor γt (RORγt)+IL-23R+ enthesis-resident lymphocytes. Fetal thymus-dependent γ/δ T cells were the main source of IL-17A at the enthesis. Under inflammatory conditions, γ/δ T cells increased in number at the Achilles tendon enthesis, aortic root, and adjacent to the ciliary body.

Conclusion: Entheseal γ/δ T cells are derived from fetal thymus and are maintained as self-renewing tissue-resident cells. As main IL-17A producers within tissues exposed to mechanical stress including enthesis, γ/δ T cells are key players in the pathogenesis of IL-23-induced local inflammation.

MeSH terms

  • Achilles Tendon / immunology*
  • Achilles Tendon / pathology
  • Animals
  • Ankle Joint / immunology
  • Ankle Joint / pathology
  • Aortic Valve / immunology*
  • Aortic Valve / pathology
  • Ciliary Body / immunology*
  • Ciliary Body / pathology
  • Enthesopathy / immunology
  • Enthesopathy / pathology
  • Flow Cytometry
  • Green Fluorescent Proteins / genetics
  • Interleukin-17 / immunology
  • Interleukin-23 / immunology*
  • Interleukins / immunology
  • Mice
  • Mice, Transgenic
  • Microscopy, Fluorescence
  • Nuclear Receptor Subfamily 1, Group F, Member 3 / immunology
  • Receptors, Antigen, T-Cell, gamma-delta / immunology*
  • Spondylarthropathies / immunology*
  • Spondylarthropathies / pathology
  • T-Lymphocyte Subsets / immunology*
  • T-Lymphocyte Subsets / pathology
  • X-Ray Microtomography


  • Il17a protein, mouse
  • Interleukin-17
  • Interleukin-23
  • Interleukins
  • Nuclear Receptor Subfamily 1, Group F, Member 3
  • Receptors, Antigen, T-Cell, gamma-delta
  • Rorc protein, mouse
  • Green Fluorescent Proteins
  • interleukin-22