Background/Purpose: Multiple lines of evidence suggest a critical role for the IL-23/IL-17A axis in spondyloarthritis. In susceptible inbred strains, hydrodynamic injection of IL-23 minicircles into adult mice induces an inflammatory disease with phenotypic features of human spondyloarthritis. IL-23 receptor expressing tissue-resident CD3+CD4-CD8- double negative (DN) innate T cells have been proposed to mediate disease pathogenesis in this model. The goal of this project was to investigate factors controlling the generation and function of these IL-23 responsive innate T cells.

Methods:   C57BL/6 wildtype (WT), TCRγδ-/-, IL1R1-/-, IL23R-GFP, Tap1-/- and MHC II-/- mice were analyzed at 8 weeks of age. Single cell suspensions from blood, liver, spleen, skin and the Achilles tendon enthesis were analyzed by multicolor flow cytometry. IL-17A production was measured by intracellular staining after stimulation with cytokines (IL-1β, IL-23 or IL-1β + IL-23) or PMA/Ionomycin in the presence of Golgi-Stop for 4 hours.

Results:   In WT mice, the CD3+ DN T cell compartment comprised both TCRαβ+ and TCRγδ+ cells with frequencies varying between tissues. Both subsets were present in MHC class I deficient Tap1-/- mice and in MHC II-/- mice. In TCRγδ-/- mice, an expanded population of DN TCRαβ+ cells compensated numerically for the absence of γδ T cells. Upon in vitro stimulation with IL-23, both TCRαβ+ and TCRγδ+ subsets depended on an additional IL-1 receptor signal for IL-17A induction. While γδ T cells were the predominant IL-17A producing subset in WT splenocytes stimulated with IL-1β + IL-23, the frequency of total IL-17A positive cells in TCRγδ-/- mice was unchanged, attributable to a compensatory increase of IL-17A production by DN TCRαβ+ cells. PMA/Ionomycin stimulation resulted in the recruitment of additional cell types producing IL-17A including CD4+ TCRαβ+ cells. PMA/Ionomycin-induced IL-17A production did not require IL-1R or IL-23R signals.

Conclusion:   Tissue resident CD3+ DN T cells in mice are either TCRαβ+ or TCRγδ+. IL-23 induced induction of IL-17A by either subset is strictly dependent on a second signal through the IL-1 receptor. DN TCRαβ+ T cells compensate for the absence of γδ T cells in TCRγδ-/- mice suggesting functional overlap in vivo.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/tissue-resident-il-23-responsive-innate-t-cells-in-mice-comprise-tcr%ce%b1%ce%b2-and-tcr%ce%b3%ce%b4-subsets-with-overlapping-function/