Elevated expression of interleukin-37 in patients with rheumatoid arthritis.

AIM: This study aims to discuss plasma and messenger RNA (mRNA) levels of interleukin (IL)-37 in rheumatoid arthritis (RA) patients and evaluate the potential of plasma IL-37 as a biomarker for RA.

METHOD: Plasma IL-37 levels and IL-37 mRNA relative concentrations were measured by enzyme-linked immunosorbent assay (ELISA) and quantitative reverse transcriptase-polymerase chain reaction (RT-PCR). We discussed the association of IL-37 levels and clinical, laboratory parameters in RA patients in a training cohort. Plasma IL-37 levels were tested for discriminatory capacity by receiver operating characteristic (ROC) curve analysis. We then validated plasma IL-37 expression in a cohort of 598 patients (230 RA, 107 systemic lupus erythematosus [SLE], 100 osteoarthritis [OA], 62 gout, 51 primary Sjögren's syndrome [pSS], 48 ankylosing spondylitis [AS]).

RESULTS

Both plasma levels of IL-37 and mRNA levels of IL-37 were elevated in RA patients compared to those in healthy controls in the training cohort, and there was a good diagnostic ability to predict RA (area under the curve [AUC] = 0.97). Plasma IL-37 levels were significantly related to Disease Activity Score of 28 joints - erythrocyte sedimentation rate (DAS28-ESR) (rs  = 0.459, P < 0.001). The levels of IL-37 mRNA were related to plasma IL-37 levels (rs  = 0.642, P < 0.001), DAS28-ESR (r = 0.641, P < 0.001) and C-reactive protein (rs  = 0.603, P < 0.001). In the validation cohort, when plasma IL-37 in RA patients compared with that in SLE, OA, gout, pSS and AS patients, the AUC was 0.86, 0.87, 0.91, 0.87, 0.92, respectively.

CONCLUSION

IL-37 expression was increased in RA patients, and correlated with disease activity. IL-37 may be a biomarker for the diagnosis of RA.