Laminin distribution and autoantibodies to laminin in dilated cardiomyopathy and myocarditis.

With the use of the enzyme-linked immunosorbent assay technique and indirect immunofluorescence, we determined the frequency of antibodies to laminin (a noncollagenous protein of basement membrane) and their influence on endomyocardial laminin distribution in 132 patients suffering from dilated cardiomyopathy and myocarditis. Seventy-eight percent of 91 patients with dilated cardiomyopathy and 73% of 41 patients with myocarditis exhibited significantly elevated anti-laminin antibody levels compared with 68 apparently healthy persons. A positive correlation was found between hemodynamic data and irregular myocardial immunofluorescence laminin staining patterns in dilated cardiomyopathy and myocarditis. With regard to recent studies, these data suggest that antibodies to laminin in dilated cardiomyopathy and myocarditis enhance clusters of cell-surface laminin, inducing an alteration of the cytoskeleton, which may account for functional abnormalities in dilated cardiomyopathy and myocarditis. Considering the fact that optical microscopy is unable to resolve sarcolemmal structures proper from the basement membranes, the high prevalence of laminin autoantibodies in dilated cardiomyopathy and myocarditis raises doubts as to the diagnostic value of direct immunofluorescence findings.