Drivers of Inflammation in Psoriatic Arthritis: the Old and the New

Charlotte O’Brien-Gore, Elizabeth H. Gray, Lucy E. Durham, Leonie S. Taams, Bruce W. Kirkham*

*Corresponding author for this work

Research output: Contribution to journalReview articlepeer-review

9 Citations (Scopus)


Purpose of Review: The recognition that IL-17 is produced by many lymphoid-like cells other than CD4+ T helper (Th17) cells raises the potential for new pathogenic pathways in IBD/psoriasis/SpA. We review recent knowledge concerning the role of unconventional and conventional lymphocytes expressing IL-17 in human PsA and axSpA. Recent Findings: Innate-like lymphoid cells, namely gamma delta (γδ) T-cells, invariant natural killer T (iNKT) cells and mucosal-associated invariant T (MAIT) cells, together with innate lymphoid cells (ILCs) are found at sites of disease in PsA/SpA. These cells are often skewed to Type-17 profiles and may significantly contribute to IL-17 production. Non-IL-23 dependent IL-17 production pathways, utilising cytokines such as IL-7 and IL-9, also characterise these cells. Both conventional CD4 and CD8 lymphocytes show pathogenic phenotypes at sites of disease. Summary: A variety of innate-like lymphoid cells and conventional lymphocytes contribute towards IL-17-mediated pathology in PsA/SpA. The responses of these cells to non-conventional immune and non-immune stimuli may explain characteristic clinical features of these diseases and potential therapeutic mechanisms of therapies such as Jak inhibitors.

Original languageEnglish
Article number40
JournalCurrent Rheumatology Reports
Issue number6
Publication statusPublished - Jun 2021


  • Innate immunity
  • Interleukin-17
  • Psoriatic arthritis
  • Spondyloarthritis
  • Synovial fluid


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