Circulating anti-heart antibodies in heart diseases detected using an immunofluorescent technique

Enzyme-linked immunosorbent assay for anti-tropomyosin antibodies and its clinical application to various heart diseases

Tropomyosin is one of the key proteins for muscle contraction. We developed an enzyme-linked immunosorbent assay for antibodies to porcine muscle tropomyosin and measured serum anti-tropomyosin antibodies in patients with heart diseases and in normal controls. The mean values of absorbance in the ELISA assay of patients with ischemic heart disease (n=36, P<0.001), dilated cardiomyopathy (n=28, P<0.005), valvular heart disease (n=27, P<0.05), and collagen disease (n=38, P<0.05) were significantly higher than those of normal controls (n=53), but the value in patients with hypertrophic cardiomyopathy (n=19) was not significantly different from that of normal controls. When the cut-off value was fixed at the mean+2 SD of absorbance in normal controls, positive reactions were found in 19.4%, 7.1%, 18.5% and 15.8% of patients with ischemic heart disease, dilated cardiomyopathy, valvular heart disease, and collagen disease, respectively. An inhibition study revealed that anti-tropomyosin antibodies were different from anti-myosin antibodies, but there was a partial cross-reactivity between the two. Thus, there was a weak correlation of the titers of the two types of antibody within the group of heart diseases. These data indicate that measurement of anti-tropomyosin antibodies by ELISA is helpful for detecting autoimmune abnormalities in various heart diseases.