Role of anti-DFS70 antibodies in idiopathic interstitial pneumonia and in connective tissue disease associated interstitial lung disease
Anti-DFS70 antibodies, corresponding to the dense fine speckled ANA indirect immunofluorescence pattern in HEp-2 substrates, have been observed in chronic inflammatory conditions, cancer and in healthy individuals but only in a small percentage of patients with systemic autoimmune rheumatic diseases. The aim of this study was to investigate the role of anti-DFS70 antibodies as biomarker in ILD. We evaluated its value to distinguish connective tissue disease associated interstitial lung disease (CTD-ILD) from idiopathic interstitial pneumonia (IIP). In addition, we explored potential correlations between anti-DFS70 antibodies and clinical parameters. Methodologically, serum samples were collected from 49 healthy controls, 35 scleroderma-ILD (SSc-ILD) patients as negative controls for anti-DFS70 antibody, and 260 patients with ILDs. The ILD patients included 100 nonspecific interstitial pneumonia (NSIP) and 160 idiopathic pulmonary fibrosis (IPF) patients. The serum anti-DFS70 antibodies were assessed by enzyme-linked immunosorbent assay. The frequency and levels of serum anti-DFS70 antibodies were lower in ILD and SSc-ILD patients compared to healthy controls. Thirty-seven patients developed CTD during 24 months of follow-up (3 initial IPF and 34 initial idiopathic NSIP patients), most of them combined with ANA positivity and anti-DFS70 antibody negativity. Anti-DFS70 antibodies were not significantly different between CTD-ILD and idiopathic ILD. Anti-DFS70 antibody concentrations were inversely correlated with pulmonary functions in iNSIP. In conclusion, the frequency and levels of serum anti-DFS70 antibodies are markedly decreased in patients with ILDs. Anti-DFS70 antibodies may play a role to predict CTD development in ILD patients.