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.