Elevation of anti-cytokeratin 18 antibody and circulating cytokeratin 18: Anti-cytokeratin 18 antibody immune complexes in sera of patients with idiopathic pulmonary fibrosis

In this study, we hypothesize that anti-cytokeratin Is (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.