CD274 and atrial fibrillation: The results showed that PD-L1 expression on mDCs in AF patients was significantly down-regulated (P < 0.001) than healthy controls (0.95 ± 0.19), and persistent AF group (0.25 ± 0.08) was lower than paroxysmal AF group (Fig.2B; 0.57 ± 0.16).