Objectives Murine models of interleukin (IL)-23-driven spondyloarthritis (SpA) have demonstrated entheseal accumulation of γδT-cells which were responsible for the majority of local IL-17A production. However, IL-23 blockers are ineffective in axial inflammation in man. This study investigated γδT-cell subsets in the normal human enthesis to explore the biology of the IL-23/17 axis.
Methods Human spinous processes entheseal soft tissue (EST) and peri-entheseal bone (PEB) were harvested during elective orthopaedic procedures. Entheseal γδT-cells were evaluated using immunohistochemistry and isolated and characterised using flow cytometry. RNA was isolated from γδT-cell subsets and analysed by qPCR. Entheseal γδT-cells were stimulated with phorbol 12-myristate 13-acetate (PMA) and ionomycin, anti-CD3/28 or IL-23 and IL-17A production was measured by high-sensitivity ELISA and qPCR.
Results Entheseal γδT-cells were confirmed immunohistochemically with Vδ1 and Vδ2 subsets that are cytometrically defined. Transcript profiles of both cell populations suggested tissue residency and immunomodulatory status. Entheseal Vδ2 cells expressed high relative abundance of IL-23/17-associated transcripts including IL-23R, RORC and CCR6, whereas the Vδ1 subset almost completely lacked detectable IL-23R transcript. Following PMA stimulation IL-17A was detectable in both Vδ1 and Vδ2 subsets, and following CD3/CD28 stimulation both subsets showed IL-17A and IL-17F transcripts with neither transcript being detectable in the Vδ1 subset following IL-23 stimulation.
Conclusion Spinal entheseal Vδ1 and Vδ2 subsets are tissue resident cells with inducible IL-17A production with evidence that the Vδ1 subset does so independently of IL-23R expression.
- ankylosing spondylitis
- T cells
- psoriatic arthritis
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Handling editor Josef S Smolen
CB and DGM contributed equally.
Correction notice This article has been corrected since it published Online First. The author affiliations and order of authors have been updated.
Contributors The listed authors made the following contributions to this manuscript: Experimental design—RJC, CB, AD, DGM, DN. Preparing the manuscript—RJC, CB, AW, EMF, PL, RD, AK, PM, AD, HMO, DN, DGM. Performing the experiments—RJC, CB, EMF, RD, PL, AK, PM, AD. Study concept—RJC, CB, DN, DMG. Final approval—RJC, CB, AW, HMO, DN, DMG.
Funding Novartis Global research grant (CB), Pfizer investigator initiated research grant (RJC).
Competing interests None declared.
Patient consent for publication Not required.
Ethics approval Leeds East Research Ethics Committee 06/Q1206/127, Greater Manchester West Ethics Committee 16/NW/0797.
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement Data are available upon reasonable request.
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