Circulating cytokeratin 8:anti-cytokeratin 8 antibody immune complexes in sera of patients with pulmonary fibrosis

Background: It has been suggested that the humoral immune system plays a role in the pathogenesis of idiopathic pulmonary fibrosis (IPF) and pulmonary fibrosis associated with collagen vascular disorders (PF-CVD). Although circulating immune complexes in patients' sera have been suggested, none of the antigens have been characterized. Objectives: The purpose of this study is to characterize the antigen of the immune complexes in patients' sera of pulmonary fibrosis. Methods: As we previously established that one of the antibodies against A549 cells (lung alveolar type II cells) was anticytokeratin 8 (CK8), we confirmed the existence of anti-CK8 antibody in patients' sera by Western immunoblot. In addition, we tried to demonstrate circulating CK8:anti-CK8 immune complexes in patients' sera by Western immunoblot. Furthermore, we established an enzymelinked immunosorbent assay to quantitate CK8:anti-CK8 immune complexes. Results: In patients with pulmonary fibrosis, anti-CK8 antibodies were dearly demonstrated in sera by Western immunoblot. In addition, circulating CK8:anti-CK8 immune complexes were also clearly demonstrated by Western immunoblot. It was possible to establish ELISA to quantitate CK8:anti-CK8 immune complexes. If the cutoff value, which was determined based on the highest value of normal volunteers, was introduced, high CK8:anti-CK8 antibody complexes were demonstrated in 9 of 31 patients (29.0%) with IPF and PF-CVD. Conclusions: This is the first study to clarify the antigen of the circulating immune complex in sera of patients with IPF. These results suggest that circulating CK8:anti-CK8 immune complexes may have played a role in the process of lung injury in pulmonary fibrosis. Copyright(C)2000S.KargerAG,Basel.