IL-17A was prevalent in sera from patients with active systemic JIA, while both ex vivo and in vitro experiments revealed that γ/δ T cells overexpressed this cytokine.
Of the ILC subsets, the frequency of NCR- ILC3s in JIA SFMCs displayed the strongest positive association with clinical measures, which was mirrored by an expansion in IL-17A+CD4+, IL-17A+CD8+, and IL-17A+ γδ T cells.
IL-17+ T cell numbers were higher in patients with extended oligoarthritis, the more severe subtype of JIA, as compared with patients with persistent oligoarthritis, the milder subtype (P = 0.046).
Interleukin 17 levels are increased in juvenile idiopathic arthritis synovial fluid and induce synovial fibroblasts to produce proinflammatory cytokines and matrix metalloproteinases.