Detection of serum cytokines in patients with dermatomyositis and their clinical significance

Abstract

Objective To explore the association of serum cytokine levels with disease activity in patients with dermatomyositis (DM) and clinically amyopathic dermatomyositis (CADM) , especially their association with skin lesions and interstitial lung disease (ILD) . Methods Enzyme-linked immunosorbent assay (ELISA) and cytometric beads array (CBA) were performed to detect the serum levels of interleukin (IL) -2, IL-4, IL-6, IL-10, IL-17A, IL-18, tumor necrosis factor (TNF) and interferon (IFN) -γ in 40 patients with DM or CADM, as well as in 16 health checkup examinees (healthy control group) . Then, the association of serum cytokine levels with skin lesions, inflammatory biomarkers and severity of ILD was analyzed. Results The patients with DM/CADM showed significantly higher serum levels of IL-6 (37.8 ± 45.8 pg/ml) , IL-10 (16.1 ± 7.2 pg/ml) and IL-18 (492.0 ± 193.1 pg/ml) compared with the healthy controls (12.0 ± 2.7 pg/ml, 7.7 ± 1.4 pg/ml, 191.1 ± 39.2 pg/ml, respectively, all P < 0.001) , and there were no significant differences in the serum levels of the other 5 cytokines between the above 2 groups. The serum level of IL-6 was significantly higher in patients with elevated erythrocyte sedimentation rate (ESR) than in those with normal ESR (49.7 ± 46.8 pg/ml vs. 29.1 ± 45.4 pg/ml, P= 0.008) . The patients with raised C-reactive protein (CRP) levels showed significantly higher serum levels of IL-6 (68.7 ± 59.7 pg/ml) and IL-18 (635.1 ± 232.8 pg/ml) compared with those with normal CRP levels (IL-6: 30.6 ± 40.3 pg/ml, P= 0.013; IL-18: 440.2 ± 164.7 pg/ml, P= 0.020) . Moreover, the patients with elevated levels of lactate dehydrogenase (LDH) showed significantly higher serum levels of IL-10 (18.4 ± 6.9 pg/ml) , IL-17A (19.6 ± 6.7 pg/ml) and IL-18 (529.4 ± 197.2 pg/ml) compared with those with normal LDH levels (IL-10: 10.7 ± 4.8 pg/ml, P < 0.001; IL-17A: 11.4 ± 6.6 pg/ml, P= 0.001; IL-18: 404.9 ± 158.0 pg/ml, P= 0.037) . No significant difference in the cytokine levels was observed between the patients with elevated creatine kinase (CK) levels and those with normal CK levels. The patients with Gottron′s papules/sign showed significantly higher serum levels of IL-18 (513.7 ± 187.2 pg/ml) compared with those without Gottron′s papules/sign (297.1 ± 140.4 pg/ml, P < 0.05) . The serum levels of IL-10 and IL-18 were significantly higher in the patients with DM/CADM complicated by ILD (18.0 ± 6.7 pg/ml, 552.3 ± 192.8 pg/ml, respectively) than in those without ILD (11.6 ± 6.5 pg/ml, 351.4 ± 101.0 pg/ml, respectively, both P= 0.001) . Conclusion Serum levels of IL-6, IL-10 and IL-18 are highly associated with inflammatory biomarkers, skin lesions and ILD in patients with DM/CADM. Key words: Dermatomyositis; Cytokines; Lung Diseases, Interstitial; Interstitial lung disease; Clinically amyopathic dermatomyositis