Soluble macrophage-mannose receptor, CD206 (sCD206): A new potential biomarker for idiopathic pulmonary fibrosis

Effective biomarkers for monitoring and predicting progression of idiopathic pulmonary fibrosis (IPF), a debilitating scarring lung disease, are currently insufficient. Markers of alternatively activated macrophages, and their soluble (s) forms in serum have been associated with various fibrotic diseases. In this study, we investigated the association of three macrophage biomarkers (sCD163, sCD206 and sSIRPα) with prognosis and clinical severity in patients with IPF.

Serum samples were collected from 149 IPF patients at baseline and after 12 and 36 months. Levels of sCD206, sCD163, and sSIRPα were quantified using enzyme-linked immunosorbent assays.

Levels of sCD206, sCD163, and sSIRPα were stable and did not significantly increase over time. Contrary to sCD163 and sSIRPα, sCD206 demonstrated repeated significant correlations to routine biochemical parameters (positive correlation to lactate dehydrogenase, p = 0.010, and C-reactive protein, p = 0.000; negative correlation to albumin, p = 0.003, and haemoglobin, p = 0.014) at baseline. At baseline, higher levels of sCD206 were significantly associated with lower results for forced vital capacity, 6-min walk test distance, and more shortness of breath (p = 0.000, p = 0.018, and p = 0.020, respectively). By both unadjusted and adjusted Cox regression analysis, IPF patients with sCD206 levels >0.2815 mg/L had a significantly increased risk of dying (Hazard ratio (HR): 2.60 (95% CI 1.59-4.24), p < 0.001 and HR: 2.17 (95% CI 1.30-3.62), p = 0.003, respectively).

sCD206 is associated with both IPF disease severity and mortality. The role of CD206+ macrophage function in IPF and the potential prognostic value of sCD206 should be further investigated.