Abstract
Objective To investigate the role of soluble interleukin-2R (sIL-2R) in idiopathic inflammatory myopathies (IIM). Methods Serum sIL-2R levels were measured in 74 dermatomyositis (DM), 16 immune-mediated necrotizing myopathy (IMNM), 24 rheumatoid arthritis (RA), 20 systemic lupus erythematosus (SLE), and 20 healthy controls (HCs) by chemiluminescent immunometric assay. Clinical features and laboratory data were collected from electronic medical record. Disease activity was evaluated by using physician global disease activity and myositis disease activity assessment visual analog scale (MYOACT) on admission. 20 DM patients were followed. Serum sIL-2R levels were analyzed and compared with clinical features, laboratory data, and measures of disease activity. Results Serum sIL-2R levels were significantly higher in DM patients than in IMNM patients and HCs (648.8 ± 433.1 U/ml vs. 352.3 ± 126.0 U/ml and 648.8 ± 433.1 U/ml vs. 285.8 ± 101.9 U/ml, respectively; all P < 0.001), while there was no significant difference between IMNM and HCs. There were also no significant differences of sIL-2R levels in DM, SLE, and RA. Importantly, serum sIL-2R levels were significantly higher in treatment-naïve or active DM patients than those that are not (1100.9 ± 550.4 U/ml vs. 615.6 ± 330.4 U/ml, P = 0.006; 808.8 ± 421.6 U/ml vs. 339.8 ± 103.4 U/ml, P < 0.001). DM patients with skin ulcers had significantly higher sIL-2R levels than those without (889.3 ± 509.9 U/ml vs. 640.0 ± 368.7 U/ml, P = 0.023). Cross-sectional analysis in DM showed that sIL-2R levels positively correlated with CK, ESR, CRP, ferritin, physician VAS, and MYOACT scores (rho = 0.278, rho = 0.474, rho = 0.469, rho = 0.454, r = 0.646, and r = 0.600, respectively; all P < 0.05), negatively correlated with T cell counts and MMT8 scores (r = −0.380, P = 0.002; rho = −0.394, P = 0.001). Follow-up study showed that changes in sIL-2R levels after treatment correlated with changes in physician VAS and MYOACT scores (r = 0.823 and r = 0.695, respectively; all P < 0.01). Conclusion Serum sIL-2R levels were elevated in DM but not in IMNM. Serum sIL-2R could act as a disease activity marker and be associated with ulcerative skin lesions in DM.
Highlights
The idiopathic inflammatory myopathies (IIM) are a group of autoimmune diseases affecting both adults and children
Consistent with previous studies [13, 14, 20], serum soluble interleukin-2R (sIL-2R) levels were increased in DM patients compared to healthy controls
Our study involved 16 immunemediated necrotizing myopathy (IMNM) patients, 14 of which could be classified as PM by Bohn and Peter criteria, but we found no significant difference between IMNM and healthy controls (HCs)
Summary
The idiopathic inflammatory myopathies (IIM) are a group of autoimmune diseases affecting both adults and children. Autoantibodies have been identified in over 50% patients. Myositis-specific autoantibodies (MSAs) are useful biomarkers in clinical practice and associated with unique clinical subtypes [2]. Autoimmunity is believed to have a key role in the pathogenesis of myositis. Peripheral T cell lymphopenia is a clinical phenomenon in some IIM patients and correlated with poor prognosis [3, 4]. Dysregulated signal pathways were found in peripheral blood T cells of IIM [6]. This abnormal behavior of T lymphocytes is a characteristic of the pathogenesis of IIM, the underlying mechanism remains unclear
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