PD-1/PD-L1 expression on CD(4+) T cells and myeloid DCs correlates with the immune pathogenesis of atrial fibrillation

Although immuno-inflammatory response contributes to pathogenesis of AF, molecular and cellular mechanism in this process remains poorly understood. Recently, increasing evidence suggests that Programmed death-1 (PD-1)/PD-1 ligand (PD-L) pathway may be a potential pathway participating in AF pathogenesis. In this study, we detected the PD-1 and PD-L1, 2 expression on peripheral blood function cells by flow cytometry in 91 atrial fibrillation (AF) patients and 35 healthy volunteers. The expression of PD-1 on CD(4+) T cells and PD-L1 on myeloid dendritic cells (mDCs) in AF patients is significantly down-regulated compared with healthy volunteers. In addition, the extent of PD-1/PD-L1 down-regulation is closely related with AF burden. More importantly, Allogeneic mixed leukocyte reactions (MLR) shows that the mDCs PD-L1 down-regulation is associated with increased T cell (CD(4+) and CD(8+)) proliferation, increased type 1 effector cytokines (IL-2 and IFN-γ) secretion, and decreased type 2 effector cytokine (IL-10) secretion. Then, PD-L1 up-regulation by the stimulation of IFN-α can significantly convert this representation. Collectively, our report suggest that T(CD(4+))/mDCs-associated PD-1/PD-L1 pathway plays a key role in AF immune regulation. PD-1/PD-L1 down-regulation in AF patients promotes T cells function and may contribute to AF pathogenesis.