The blockade of PD‐1/PD‐L1 pathway promotes the apoptosis of CD19 + CD25 + Bregs and suppresses the secretion of IL‐10 in patients with allergic rhinitis

PD‐1/PD‐L1 pathway is crucial to immune regulation by controlling the balance between T cell tolerance and activation. However, the association between PD‐1/PD‐L1 pathway and regulatory B cells has not been fully investigated in allergic rhinitis. In this study, we detected the number of peripheral CD19 + CD25 + Bregs and the expression of IL‐10 on this cell subset in healthy control and patients with allergic rhinitis using flow cytometry. Then, we evaluated the level of PD‐L1 in CD19 + CD25 + Bregs and investigated the correlation between PD‐L1 and CD4 + follicular T helper cells. Finally, we studied the effects of anti–PD‐L1 on the apoptosis of Bregs and the production of IL‐10. Comparing with healthy controls, the percentage of CD19 + CD25 + Bregs and the expression of IL‐10 were both significantly decreased in AR group. In addition, the expression of PD‐L1 on CD19 + CD25 + Bregs was also lower in allergic rhinitis patients. Interestingly, a negative correlation was found between the expression of PD‐L1 + Bregs and CD4 + CXCR5 + follicular T helper cells. In vitro assay revealed that anti–PD‐L1 promoted Bregs apoptosis and inhibited the expression of IL‐10 in CD19 + CD25 + Bregs. Collectively, these results suggest that PD‐L1 expressed on CD19 + CD25 + Bregs may be a potential regulator in the treatment of allergic rhinitis. Blockade of PD‐1/PD‐L1 pathway might be a valuable pathogenic target for allergic rhinitis through inhibiting the secretion of immunosuppressive cytokine and promoting CD19 + CD25 + Bregs apoptosis.