Cross-Priming Dendritic Cells Exacerbate Immunopathology after Ischemic Tissue Damage in the Heart.

Background: Ischemic heart disease is a leading cause of heart failure and despite advanced therapeutic options, morbidity and mortality rates remain high. Although acute inflammation in response to myocardial cell death has been extensively studied, subsequent adaptive immune activity and anti-heart autoimmunity may also contribute to the development of HF. After ischemic injury to the myocardium, dendritic cells (DC) respond to cardiomyocyte necrosis, present cardiac antigen to T cells and potentially initiate a persistent autoimmune response against the heart. Cross-priming DC have the ability to activate both CD4+ helper and CD8+ cytotoxic T cells in response to necrotic cells and may thus be crucial players in exacerbating autoimmunity targeting the heart. This study investigates a role for cross-priming DC in post-MI myocardial impairment through presentation of self-antigen from necrotic cardiomyocytes to cytotoxic CD8+ T cells. Methods: We induced type-2 myocardial infarction (MI)-like ischemic injury in the heart by treatment with a single high dose of the beta-adrenergic agonist isoproterenol. We characterized the DC population in the heart and mediastinal lymph nodes and analyzed long-term cardiac immunopathology and functional decline in wild type and Clec9a-depleted mice lacking DC cross-priming function. Results: A diverse DC population, including cross-priming DC, is present in the heart and activated after ischemic injury. Clec9a-/- mice deficient in DC cross-priming are protected from long-term immune-mediated myocardial damage and decline of cardiac function, likely due to dampened activation of cytotoxic CD8+ T cells. Conclusions: Activation of cytotoxic CD8+ T cells by cross-priming DC contributes to exacerbation of post-ischemic inflammatory damage of the myocardium and corresponding decline in cardiac function. Importantly, this provides novel therapeutic targets to prevent immune-mediated worsening of post-ischemic HF.