Abstract
We measured the interleukin-34 (IL-34) level in sera from patients with systemic lupus erythematosus (SLE) and discoid lupus erythematosus (DLE) using an enzyme-linked immunosorbent assay (ELISA). Blood tests, including assays to determine C-reactive protein (CRP), complement (C) 3, C4, immunoglobulin (Ig) A, IgG, IgM, anti-double-stranded DNA antibody (Anti-dsDNA Ab) and hemoglobin (Hb) levels and white blood cell (WBC) and platelet (PLT) counts, were performed using standard methods. Lupus nephritis (LN) was diagnosed according to the American College of Rheumatology (ACR) renal criteria. The SLE disease activity was scored using the SLE Disease Activity Index (SLEDAI). Among the 110 SLE cases, IL-34 could be detected in 79 cases (71.8%). IL-34 was barely detected in the control group. The serum level of IL-34 was significantly higher in the SLE group. No change was observed in the serum IL-34 concentration in the SLE patients regardless of LN status. Correlations were observed between the serum IL-34 level and the disease activity parameters. The SLE patients with detectable IL-34 levels had higher SLEDAI and IgG concentrations and lower C3 and Hb levels than patients with undetectable IL-34 levels. Therefore, IL-34 could be a potential disease activity marker for SLE.
Highlights
Many cytokines have been shown to play important roles in the pathogenesis of systemic lupus erythematosus (SLE), and several biological products have been used in SLE patients
This study is the first to show that the IL-34 level is elevated in SLE patients and correlated with the disease activity
We reported that the serum IL-34 level was significantly elevated in the SLE patients compared to that in the healthy controls
Summary
Many cytokines have been shown to play important roles in the pathogenesis of SLE, and several biological products have been used in SLE patients. Using the current therapeutic strategies, only a very small proportion of SLE patients achieve long-term remission[4]. Interleukin (IL)−34 is a newly discovered cytokine that has no significant amino acid sequence homology to other cytokines[5]. Because IL-34 is an alternative ligand of the colony-stimulating factor-1 receptor (CSF-1R), IL-34 binds to CSF-1R and promotes the differentiation and proliferation of lymphocytes and the expression of cytokines, leading to inflammatory lesions and autoimmunity[5,7].
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