TNF and viral myocarditis: Gluck et al. (2001) suggested that the high level of cytokines in chronic viral myocarditis mice aggravates the damage of connective tissue. TNF-α increased ECM protein proliferation and induced the apoptosis and necrosis of myocardial cells, which are ultimately replaced or repaired by fibrous tissue. IL-6 and IL-1β directly induce myocardial fibrosis (Pulkki, 1997; Ono et al., 1998; Abreu et al., 2002; Eriksson et al., 2003).