Critical Cytokine Pathways to Cardiac Inflammation

Infectious disease is frequently cited as a precursor of subsequent autoimmune disease in genetically susceptible hosts. However, the precise mechanisms required for the transition from infection to autoimmunity have not been well defined. We have developed a mouse model of autoimmune myocarditis initiated by infection with Coxsackievirus B3 to trace the cytokine pathways involved. We found that greater production of interleukin-1 beta (IL-1 beta) and tumor necrosis factor-alpha during the early innate response to virus infection is necessary and sufficient to induce a later heart-specific autoimmune disease. Severity of the autoimmune myocarditis is determined by the profile of a number of T helper 1 (Th1) and Th2 cytokines. Th2 responses are especially pronounced in the most severe forms of myocarditis where eosinophils are prominent. The Th1 pathway can lead to infiltration of the heart, but may be dampened by concurrent INF-gamma production. Th17 cytokines also contribute to disease, but the signature Th17 cytokine, IL-17A, is not required for cardiac inflammation. Rather, IL-17A is needed for progression to dilated cardiomyopathy. These findings may provide useful markers to identify individuals prone to develop an autoimmune sequel after infection and suggest future early interventions.