High serum concentrations of autoantibodies to HSP47 in nonspecific interstitial pneumonia compared with idiopathic pulmonary fibrosis

BACKGROUND: The pathological diagnosis of idiopathic interstitial pneumonias (IIP) by surgical lung biopsy is important for clinical decision-making. However, there is a need to use less invasive biomarkers to differentiate nonspecific interstitial pneumonia (NSIP) from other IIP such as usual interstitial pneumonia (UIP). Heat shock protein (HSP) 47, a collagen-specific molecular chaperone, is involved in the processing and/or secretion of procollagen. HSP47 is increased in various fibrotic diseases. We investigated the autoantibodies to HSP47 in IIPs. METHODS: We measured the serum levels of the autoantibodies to HSP47 in 38 patients with various forms of IIP [16 with idiopathic pulmonary fibrosis (IPF), 15 with idiopathic NSIP, 7 with cryptogenic organizing pneumonia (COP)] and 18 healthy volunteers. RESULTS: The serum levels of autoantibodies to HSP47 in patients with idiopathic NSIP were significantly higher than in patients with IPF (P < 0.01), COP (P < 0.05), and healthy volunteers (P < 0.05). In addition, those in fibrosing NSIP were significantly higher than those of cellular and fibrosing NSIP (p < 0.05). CONCLUSION: We found high levels of anti-HSP47 autoantibody titers in sera of patients with idiopathic fibrosing NSIP compared with other IIPs and healthy volunteers.