Interleukin-17A: a unique pathway in immune-mediated diseases: psoriasis, psoriatic arthritis and rheumatoid arthritis

Immunology. 2014 Feb;141(2):133-42. doi: 10.1111/imm.12142.


Experimental evidence points to the importance of the cytokine interleukin-17A (IL-17A) in the pathogenesis of several immunoinflammatory diseases including psoriasis, psoriatic arthritis and rheumatoid arthritis. Although a principal effector of T helper type 17 cells, IL-17A is produced by many other cell types including CD8(+) T cells and γδ T cells, and is found at high levels associated with mast cells and neutrophils at sites of skin and joint disease in humans. IL-17A up-regulates expression of numerous inflammation-related genes in target cells such as keratinocytes and fibroblasts, leading to increased production of chemokines, cytokines, antimicrobial peptides and other mediators that contribute to clinical disease features. Importantly, IL-17A must be considered within the context of the local microenvironment, because it acts synergistically or additively with other pro-inflammatory cytokines, including tumour necrosis factor. Several direct IL-17A inhibitors have shown promising activity in proof of concept and phase 2 clinical studies, thereby providing confirmation of experimental data supporting IL-17A in disease pathogenesis, although levels of response are not predicted by pre-clinical findings. IL-17A inhibitors produced rapid down-regulation of the psoriasis gene signature and high clinical response rates in patients with moderate-to-severe plaque psoriasis, consistent with an important role for IL-17A in psoriasis pathogenesis. Clinical response rates with IL-17A inhibitors in psoriatic arthritis and rheumatoid arthritis, however, were improved to a lesser degree compared with placebo, suggesting that IL-17A is either important in a subset of patients or plays a relatively minor role in inflammatory joint disease. Ongoing phase 3 clinical trials should provide further information on the role of IL-17A in these diseases.

Keywords: biological therapy; interleukin-17A; psoriasis; psoriatic arthritis; rheumatoid arthritis.

Publication types

  • Review

MeSH terms

  • Animals
  • Arthritis, Psoriatic / drug therapy
  • Arthritis, Psoriatic / etiology*
  • Arthritis, Psoriatic / immunology
  • Arthritis, Rheumatoid / drug therapy
  • Arthritis, Rheumatoid / etiology*
  • Arthritis, Rheumatoid / immunology
  • Clinical Trials as Topic
  • Humans
  • Interleukin-17 / antagonists & inhibitors
  • Interleukin-17 / physiology*
  • Psoriasis / drug therapy
  • Psoriasis / etiology*
  • Psoriasis / immunology
  • Receptors, Interleukin-17 / physiology
  • Signal Transduction / physiology


  • Interleukin-17
  • Receptors, Interleukin-17