title: Clinical associations of serum interleukin-17 in systemic lupus erythematosus.
abstract: BACKGROUND
  Serum interleukin (IL)-17 concentrations have been reported to be increased in systemic lupus erythematosus (SLE), but associations with clinical characteristics are not well understood. We characterized clinical associations of serum IL-17 in SLE.
  
  
  METHODS
  We quantified IL-17 in serum samples from 98 SLE patients studied cross-sectionally, and in 246 samples from 75 of these patients followed longitudinally over two years. Disease activity was recorded using the SLE Disease Activity Index (SLEDAI)-2k. Serum IL-6, migration inhibitory factor (MIF), and B cell activating factor of the tumour necrosis factor family (BAFF) were also measured in these samples.
  
  
  RESULTS
  Serum IL-17 levels were significantly higher in SLE patients compared to healthy donors (P <0.0001). No correlation was observed between serum IL-17 and SLEDAI-2k, at baseline or during longitudinal follow-up. However, we observed that SLEDAI-2k was positively correlated with IL-17/IL-6 ratio. Serum IL-17 was significantly increased in SLE patients with central nervous system (CNS) disease (P = 0.0298). A strong correlation was observed between serum IL-17 and IL-6 (r = 0.62, P <0.0001), and this relationship was observed regardless of disease activity and persisted when integrating cytokine levels over the period observed (r = 0.66, P <0.0001). A strong correlation of serum IL-17 was also observed with serum BAFF (r = 0.64, P <0.0001), and MIF (r = 0.36, P = 0.0016).
  
  
  CONCLUSIONS
  Serum IL-17 concentration correlates poorly with SLE disease activity but is significantly elevated in patients with CNS disease. IL-17/IL-6 ratio may be more useful than IL-17 or IL-6 alone to characterize Th17-driven disease, such as SLE. The association of other cytokines with serum IL-17 suggests that IL-17 may drive activation of diverse immune pathways in SLE.
authors: Fabien B
authors: FB
authors: Vincent
authors: Melissa
authors: M
authors: Northcott
authors: Alberta
authors: A
authors: Hoi
authors: Fabienne
authors: F
authors: Mackay
authors: Eric F
authors: EF
authors: Morand
mesh_terms: D000328:Adult; D003430:Cross-Sectional Studies; D016207:Cytokines / Q000097:blood; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D020381:Interleukin-17 / Q000097:blood* / Q000276:immunology*; D015850:Interleukin-6 / Q000097:blood / Q000276:immunology; D008180:Lupus Erythematosus, Systemic / Q000097:blood* / Q000276:immunology*; D008297:Male; D008875:Middle Aged; D012720:Severity of Illness Index
chemical_list: D016207:Cytokines; C508600:IL6 protein, human; D020381:Interleukin-17; D015850:Interleukin-6
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