IL21 and viral myocarditis: Li et al. showed that plasma and cardiac progranulin were increased in CVB3-infected WT mice, and viral myocarditis was exacerbated in CVB3-infected progranulin−/− mice with high levels of splenic and cardiac Th1 and Th17 cell proportion, which were also evident in serum levels of IFN-γ, TNF-α, IL-17A, and IL-21.