Experimental autoimmune myocarditis in A/J mice is an interleukin-4-dependent disease with a Th2 phenotype

Myocarditis in humans is often associated with an autoimmune process in whi ch cardiac myosin (CM) is a major autoantigen. Experimental autoimmune myoc arditis (EAM) is induced in mice by immunization with CM. We found that EAM in A/J mice exhibits a Th2-like phenotype demonstrated by the histological picture of the heart lesions (eosinophils and giant cells) and by the humo ral response (association of IgG1 response with disease and up-regulation o f total IgE). Blocking interleukin (IL)-4 with anti-IL-4 monoclonal antibod y (mAb) reduced the severity of EAM. This reduction in severity was associa ted with a shift from a Th2-like to a Th1-like phenotype represented by a r eduction in CM-specific IgG1; an increase in CM-specific IgG2a; an abrogati on of total IgE response; a decrease in IL-4, IL-5, and IL-13; as well as a dramatic increase in interferon (IFN)-gamma production in vitro. Based on the latter finding, we hypothesized that IFN-gamma limits disease. Indeed, IFN-gamma blockade with a mAb exacerbated disease. The ameliorating effect of IL-4: blockade was abrogated by co-administration of anti-IFN-gamma mAb. Thus, EAM represents a model of an organ-specific autoimmune disease assoc iated with a Th2 phenotype, in which IL-4 promotes the disease and IFN-gamm a limits it. Suppression of IFN-gamma represents at least one of the mechan isms by which IL-4 promotes EAM.