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Open Access Highly Accessed Research article

Clinical associations of serum interleukin-17 in systemic lupus erythematosus

Fabien B Vincent1*, Melissa Northcott2, Alberta Hoi2, Fabienne Mackay1 and Eric F Morand2

Author Affiliations

1 Department of Immunology, Monash University, Central Clinical School, Alfred Medical Research and Education Precinct (AMREP), 89 Commercial Road, Melbourne, VIC, 3004, Australia

2 Monash University Centre for Inflammatory Diseases, Southern Clinical School, Monash Medical Centre, 246 Clayton Road, Clayton, VIC, 3168, Australia

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Arthritis Research & Therapy 2013, 15:R97  doi:10.1186/ar4277

Published: 23 August 2013

Abstract

Introduction

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.

Keywords:
Autoimmunity; B cell activating factor of the tumour necrosis factor (TNF) family (BAFF); interleukin-6; interleukin-17; macrophage migration inhibitory factor (MIF); systemic lupus erythematosus (SLE); T helper 17 (Th17)