Increased IgG Antibody-Induced Cytotoxicity Against Airway Epithelial Cells in Patients with Nonallergic Asthma

IgG autoantibodies to airway epithelial cell proteins have been detected in patients with nonallergic asthma. To evaluate the functional significance of these autoantibodies, we examined the presence of IgG antibody-induced cytotoxicity against airway epithelial cells (A549) by the microcytotoxicity assay using IgG antibodies purified from patients with nonallergic asthma. IgG antibody-induced cytotoxicity (expressed as percent cell lysis) was significantly increased in nine patients with nonallergic asthma (mean +/- standard deviation; 30.6 +/- 7.3%) as compared with eight healthy controls (13.9 +/- 5.1%) and nine patients with allergic asthma (20.3 +/- 10.4%; p < 0.05). In addition, IgG antibody-induced cytotoxicity was significantly inhibited when IgG antibodies from patients with nonallergic asthma were pre-incubated with recombinant human airway epithelial cell autoantigens (cytokeratin 18 or alpha-enolase proteins; p < 0.05). These results suggest a possible involvement of IgG autoantibody-induced cytotoxicity against airway epithelial cells in the pathogenesis of nonallergic asthma.