IL21 and atrial fibrillation: Representative FACS dot plots of cytokine production from CD4+ T cells are shown in Fig. 4A. Before antiviral treatment (at 26–28 weeks of gestation, Fig. 4B), CD4+ T cells in AF mothers secreted more IFN-γ, IL-21, and IL-2 than CD4+ T cells in NAF mothers (p = 0.007, p = 0.035, p = 0.021).