Background/Purposes: IgG4-related disease (IgG4-RD) is a lymphoproliferative disorder characterized by allergic manifestations and severe fibrosis in the lesions. CC-chemokine ligand 18 (CCL18) level is a substantial biomarker for fibrotic diseases such as systemic sclerosis. The objective of this study was to investigate association between serum CCL18 levels and clinical findings in patients with IgG4-RD.
Methods: Twenty-eight consecutive, treatment-naïve patients with IgG4-RD and 16 healthy volunteers were enrolled. All IgG4-RD patients fulfilled the 2011 comprehensive diagnostic criteria. Disease activity of the patients was assessed by the IgG4-RD responder index (IgG4-RD RI). Serum CCL18 levels were measured by using human CCL18/PARC Quantikine ELISA Kit (R&D Systems). The correlation between serum CCL18 levels and clinical parameters was examined.
Results: Serum CCL18 levels in patients with IgG4-RD (mean 44.7 ng/mL, range 3.6–120.9 ng/mL) were significantly higher than those in healthy volunteers (mean 18.5 ng/mL, range 0.1–63.8 ng/mL; P = 0.01). Of note, serum CCL18 levels positively correlated with IgG4-RD RI scores (ρ = 0.54, P < 0.005), the number of affected organs (ρ = 0.56, P < 0.005), or serum IgG4 levels (ρ = 0.50, P < 0.01), but not with serum IgE levels (ρ = -0.05, P = 0.79) or blood eosinophil counts (ρ = 0.18, P = 0.38). In line with that, serum CCL18 levels were not different between in IgG4-RD patients with atopic disease and those without. Moreover, serum CCL18 levels significantly decreased after glucocorticoid treatment for patients with IgG4-RD (44.7 ng/mL vs. 12.7 ng/mL, P < 0.01), which were paralleled with disease improvement.
Conclusions: Serum CCL18 level is a novel biomarker potentially valuable for evaluating disease activity and treatment response in IgG4-RD. Also, serum CCL18 levels reflect IgG4-RD state rather than allergic conditions. Our results suggest that CCL18 is involved in the process of fibrotic feature in IgG4-RD.