Elevation of Anti-Cytokeratin 18 Antibody and Circulating Cytokeratin 18: Anti-Cytokeratin 18 Antibody Immune Complexes in Sera of Patients with Idiopathic Pulmonary Fibrosis

Abstract.

In this study, we hypothesize that anti-cytokeratin 18 (CK18) antibody and CK18:anti-CK18 immune complex increase in sera in patients with idiopathic pulmonary fibrosis (IPF). To prove the existence of anti-CK18 antibodies in patients' sera, bovine CK18 was stained with patients' sera using a Western blotting. In patients with IPF, anti-CK18 antibodies were clearly demonstrated in sera by Western blotting. Then, we tried to establish an enzyme-linked immunosorbent assay (ELISA) to quantify anti-CK18 antibodies and CK18:anti-CK18 immune complexes in sera of patients with IPF. Levels of anti-human CK18 antibodies in sera of patients with IPF (0.81 ± 0.31, mean ± SD) measured by ELISA were significantly high compared with that of normal volunteers (0.45 ± 0.06, p < 0.01). In addition, levels of CK18:anti-CK18 antibody complexes in patients' sera (0.64 ± 0.35, man ± SD) significantly increased compared with those of normal subjects (0.40 ± 0.10, p < 0.01). These results suggest that anti-CK18 antibody and its immune complex may have played a role in the process of lung injury in IPF.