It has been reported that CD4 regulatory T cells can secrete regulatory cytokines (IL-10 and TGF-β) to inhibit the activities of other immunophenotypes, and thus we speculate that CD4 regulatory T cells play an important role in myocarditis (Chen et al., 2003; Jutel et al., 2003; Wan and Flavell, 2008). Here, CD4 is linked to myocarditis.