CD4 and atrial fibrillation: In the AF dataset, activated CD4+ T cell, activated CD8+ T cell, TH1, regulatory T cell, central memory CD8+ T cell, effector memory CD4+ T cell, γδT cell, effector memory CD8+ T cell, myeloid-derived suppressor cell, activated dendritic cell, immature dendritic cell, natural killer cell, macrophage, monocyte, mast cell, and neutrophil are significantly higher in AF group (P < 0.05) (Fig. 5B).