PDCD1 and Autoimmunity: Wang et al. demonstrated that fatal myocarditis developed in mice genetically predisposed the mice to systemic autoimmunity due to PD-1 deficiency, whereas in mice with genetic predisposition to autoimmunity but without PD-1 deficiency, myocarditis did not develop, suggesting that myocarditis prevention is likely to be mediated by PD-1 [38].