Complement-mediated cytotoxic activity of anti-heart antibodies present in the sera of patients with dilated cardiomyopathy.

A microcytotoxicity assay has been used to determine the cytotoxic activity of anti-heart antibodies which we have previously shown to be present with greater frequencies and reactivities in patients with dilated cardiomyopathy (DCM) than in patients with ischaemic heart disease (IHD). Serum samples from 45 patients with DCM and 43 patients with IHD were screened against W1, a transformed human fetal cardiac cell line and also against EA.hy 926, an endothelial and IBR3, a fibroblast cell line. In the presence of complement, sera from 28 (62%) DCM patients showed killing of the W1 cell line as compared to sera from 13 (30%) of IHD patients (p < 0.005) and 3 (15%) of normal individuals. In contrast, only 1 patient with DCM showed killing of the endothelial cell line and 1 patient with IHD showed killing of the fibroblast cell line. These results provide evidence for a complement-dependent, antibody-mediated mechanism of damage to cardiac myocytes which may contribute to the pathogenesis of DCM.