Characterization of murine autoimmune myocarditis induced by self and foreign cardiac myosin.

Previously we showed that autoimmune myocarditis could be induced in mice by immunization with purified murine cardiac myosin (MCM). In this study, we found that identical disease could also be induced in genetically susceptible mice by immunization with porcine cardiac myosin (PCM). The cardiac lesions induced by both antigens were characterized by extensive infiltration of the myocardium accompanied by myocyte necrosis. A novel finding was the presence of multinucleated giant cells and eosinophils in the cardiac infiltrates, in addition to a mixture of mononuclear cells and polymorphonuclear cells described previously. Immunohistochemical staining demonstrated that the mononuclear cells consisted predominantly of macrophages, CD4+ T cells and, to a lesser extent, CD8+ T cells and B cells. In addition, increased cardiac expression of adhesion molecules E-selectin, vascular cell adhesion molecule-1 (VCAM-1) and intercellular cell adhesion molecule-1 (ICAM-1) were demonstrated in mice that developed myocarditis as compared with those that did not develop disease upon immunization with either PCM or MCM. The levels of TNFalpha detected in spleen cell culture supernatant were found to be higher in mice that developed myocarditis than in those that did not develop the disease. Mice immunized with PCM generated T cells and B cells reactive not only with PCM but also with MCM, and vice versa. In addition, the serum levels of IgG1 anti-MCM antibodies produced in mice immunized with PCM as well as MCM were found to correlate positively with the development of myocarditis. Such a detailed characterization of the murine model of autoimmune myocarditis induced by PCM or MCM allowed us to compare the disease process induced by homologous self and foreign antigens.