Influence of total glucosides of paeony on PD‐1/PD‐L1 expression in primary Sjögren's syndrome

To study the influence of total glucosides of paeony (TGP) on the expression of peripheral blood programmed cell death protein 1 (PD-1) and its ligand (PD-L1) in patients with primary Sjögren's syndrome (pSS). Ten patients with new-onset pSS were selected as the experimental group and were treated with 1.8 g of TGP (the main ingredient is Radix Paeoniae Alba) daily for 3 months; furthermore, 10 physically healthy individuals were selected as the control group. Peripheral blood mononuclear cells were isolated, and flow cytometry was used to detect PD-1 expression on the surface of CD4+ T and CD8+ T lymphocytes and PD-L1 expression on the surface of CD14+ monocytes and CD19+ B cells before and after treatment in the experimental and control groups. Furthermore, plasma levels of soluble PD-1 (sPD-1), interleukin (IL)-10, and IL-17A were also determined using enzyme-linked immunosorbent assay. The PD-1 expression on the surface of CD4+ T and CD8+ T lymphocytes in the peripheral blood of patients with pSS were significantly higher than in the control group (P < 0.001). However, PD-L1 expression on the surface of CD14+ monocytes declined but not significantly (P > 0.05), and PD-L1 expression on the surface of CD19+ B cells increased significantly (P < 0.001). Moreover, sPD-1 and IL-17A levels in the plasma of the experimental group were significantly higher than in the control group (P < 0.001), but the IL-10 level was significantly lower than in the control group (P < 0.001). After TGP treatment, PD-1 expression on the surface of CD4+ T and CD8+ lymphocytes in the peripheral blood of patients with pSS had decreased significantly (P < 0.001); the PD-L1 expression on the surface of CD19+ cells had decreased significantly (P < 0.001); and the PD-L1 expression on the surface of CD14+ monocytes did not differ significantly (P > 0.05). Furthermore, the levels of sPD-1 and IL-17A in plasma had decreased (P < 0.01) and IL-10 levels had increased after TGP treatment (P < 0.01). PD-1/PD-L1 molecules expressed on the surface of T cells, B cells, and monokaryon participated in the pathogenesis and development of SS through interactions. Therefore, TGP, which may increase the expression of PD-1 and its relevant ligand PD-L1 in the peripheral blood mononuclear cells, may play a role in the pathogenesis and development of SS through the PD-1/PD-L1 pathway by regulating regulatory T cells/T helper cell 17.