[Involvement of immune system in the pathogenesis of viral myocarditis]

Myocarditis is thought to be commonly caused by various viruses, and accumulating evidence links viral myocarditis with the eventual development of dilated cardiomyopathy. Heart disease is the most prevalent cause of morbidity and mortality in developed countries. Cytokines are being increasingly recognized as an important factor in the pathogenesis of myocarditis and cardiomyopathy. Elevated levels of circulating cytokines have been reported in patients with heart failure, and various cytokines have been shown to depress myocardial contractility in vitro and in vivo. A number of reports have shown that cytokines generated by activated immune cells cause an increase in nitric oxide (NO) via induction of NO synthase. Increased generation of NO may induce myocardial damage. It has been suggested that NO can be either beneficial or harmful to the host, NO can protect the myocardium against damage from CVB3 infection by inhibiting viral replication. A better molecular understanding of the direct effect of viral infection on cardiac myocytes and the balance of beneficial and detrimental effects of the immune response will ultimately provide insight into the mechanisms by which viral infections cause cardiomyopathy in humans.