BAL cytokine profile in different interstitial lung diseases: a focus on systemic sclerosis

Background and aim: Fibrosing alveolitis develops in up to 80% of systemic sclerosis patients (SSc) but progression to end stage fibrosis occurs in about 15% of cases. Mechanisms leading to the process remain mostly unknown. We compared cytokine profiles of broncho-alveolar lavage fluids (BAL-f) from patients with SSc associated interstitial lung disease (SSc-ILD) (n. 34), idiopathic pulmonary fibrosis (IPF) (n. 13), stage 11 sarcoidosis (n. 14) and 9 controls. Methods: Interleukin (IL) 8, monocyte chemoattractant protein I (MCP-1), gamma-interferon (IFN-gamma), IL12, IL18 and IL10 and transforming growth factor-beta (TGF-beta) were assessed by ELISA in concentrated BAL-f. Results: Levels of IL8 and MCP-1 were significantly elevated in SSc-ILD and in IPF as compared with controls (Mann Whitney test p < 0.05), while MCP-1 values were significantly lower in SSc-ILD than in IPF. A significant correlation between neutrophils and IL8 levels (p = 0.047), as well as between cosinophils and MCP-1 levels (p = 0.004) was also observed. IFN-gamma levels were slightly higher than normal only in sarcoidosis (p = 0.06), whereas IL12 levels increased both in sarcoidosis and SSc-ILD (p < 0.05). No differences were found in IL18 and TGF-beta levels. Finally, IL10 levels were higher in SSc-ILD and sarcoidosis than in controls and IPF (p < 0.05). Conclusion: BAL-f cytokine profile differentiates ILD associated with SSc from IPF. The lower expression of MCP-1 and the higher expression of the anti-fibrotic IL12 and the anti-inflammatory IL10, observed both in sarcoidosis and in SSc-ILD, could account for the better prognosis of these ILDs. Further longitudinal studies are required to confirm whether a different cytokine phenotype may be considered predictive of clinical outcome in SSc-ILD.