Elevated serum interleukin-35 is associated with disease activity in patients with systemic lupus erythematosus

Regional variations in serum IL-35 levels and association with systemic lupus erythematosus: a systematic review and meta-analysis

Interleukin (IL)-35 is an anti-inflammatory cytokine that regulates autoimmune diseases, including systemic lupus erythematosus (SLE). However, the association between the cytokine and disease may vary by geographical region. This study performed a meta-analysis to quantitatively assess the correlation between the serum IL-35 levels in SLE patients and sub-group analyses were conducted. Four main electronic databases-Scopus, Embase, Science Direct, PubMed-were searched for relevant studies. After a database search, Endnote software was used to find and remove duplicate studies. Random-effects models were used to estimate standard mean differences in serum/plasma IL-35 levels by Hedges' g with 95% confidence intervals (CIs). Publication bias was assessed with funnel plots, and risk of bias was assessed according to the Newcastle-Ottawa Scale (NOS). Sixteen studies met the eligibility criteria and were included in a qualitative review; data from 15 studies were included in the meta-analysis. Total IL-35 levels (pg/mL) did not differ among patients with active SLE and healthy controls (Hedges's g: 0.22, 95% CI - 0.51, 0.95, p = 0.55). Sub-group analysis revealed that IL-35 levels in patients with active SLE were lower than in healthy controls in Chinese studies (Hedges's g: - 3.11, 95% CI - 5.72, - 0.51), but not in non-Chinese studies (Hedges's g: 1.63, 95% CI - 0.31, 3.57). This regional difference was statistically significant (p < 0.01). The analysis comparing patients with inactive SLE and healthy controls showed a similar trend. This study suggests that serum IL-35 levels are lower in patients with SLE in studies from China, but not other regions. However, standardized protocols with large sample sizes are needed to confirm these findings.

A glance on the role of IL-35 in systemic lupus erythematosus (SLE)

It is well known that systemic lupus erythematosus (SLE) is an auto-inflammatory disease that is characterized by chronic and widespread inflammation. The exact pathogenesis of SLE is still a matter of debate. However, it has been suggested that the binding of autoantibodies to autoantigens forms immune complexes (ICs), activators of the immune response, in SLE patients. Ultimately, all of these responses lead to an imbalance between anti-inflammatory and pro-inflammatory cytokines, resulting in cumulative inflammation. IL-35, the newest member of the IL-12 family, is an immunosuppressive and anti-inflammatory cytokine secreted mainly by regulatory cells. Structurally, IL-35 is a heterodimeric cytokine, composed of Epstein-Barr virus-induced gene 3 (EBI3) and p35. IL-35 appears to hold therapeutic and diagnostic potential in cancer and autoimmune diseases. In this review, we summarized the most recent associations between IL and 35 and SLE. Unfortunately, the comparative review of IL-35 in SLE indicates many differences and contradictions, which make it difficult to generalize the use of IL-35 in the treatment of SLE. With the available information, it is not possible to talk about targeting this cytokine for the lupus treatment. So, further studies would be needed to establish the clear and exact levels of this cytokine and its related receptors in people with lupus to provide IL-35 as a preferential therapeutic or diagnostic candidate in SLE management.

Urine and serum interleukin 35 as potential biomarkers of lupus nephritis

Introduction

Lupus nephritis (LN) is considered a serious manifestation of systemic lupus erythematosus (SLE). Therefore, a reliable non-invasive biomarker is a priority for monitoring renal involvement instead of the kidney biopsy. Interleukin 35 (IL-35) has an immunosuppressive and anti-inflammatory role in many autoimmune diseases. However, its role in LN still needs to be elucidated.

Aim of the study

To evaluate urine and serum levels of IL-35 in SLE patients with LN and without nephritis identifying their potential as biomarkers of renal involvement.

Material and methods

Urine and serum levels of IL-35 were measured in 42 SLE patients, divided into 22 with LN and 20 without LN, and 20 matched healthy controls using enzyme-linked immunosorbent assay (ELISA). SLE disease activity was assessed for patients by the Systemic Lupus Erythematosus Disease Activity Index 2000 (SLEDAI-2K).

Results

Levels of serum and urine IL-35 were significantly higher (p < 0.001) in the LN group compared with those without LN and with controls. In LN patients, a strong correlation (p < 0.001) was observed between serum and urine IL-35 levels with SLEDAI-2K score (r = 0.677 and 0.806 respectively). Furthermore, proteinuria had a strong and significant correlation (p ˂ 0.001) with serum and urinary IL-35 levels in the patients with LN. Serum IL-35 had 90.9% sensitivity and 85% specificity while urine IL-35 had 95.5% sensitivity and 75% specificity to differentiate LN from healthy individuals.

Conclusions

Urine and serum IL-35 may aid in assessment of renal involvement in SLE patients, serving as potential biomarkers of LN.