Expression Characteristics And Clinical Significance Of PD-1/PD-ls In Peripheral Blood CD19~+B Cells Of Patients With Systemic Lupus Erythematosus

Background:Systemic lupus erythematosus?SLE?is a chronic autoimmune disease that affects the entire body.Abnormally active polyclonal B cells are involved in almost all stages of SLE.PD-1?Programmed Cell Death-1,CD279?is an inhibitory receptor belonging to the CD28/CTLA-4 family.Inhibitory signals produced by the interaction between PD-1 and its ligand PD-L1 or PD-L2 contribute to maintaining immune tolerance.The expression level of PD-1/PD-Ls on B cells may play an important role in the pathogenesis of SLE.Objective:The purpose of this study was to determine the expression of PD-1/PD-Ls in CD19⁺B-cells and CD19⁺CD20^-B-cells,and to explore its possible role in the occurrence and development of SLE.Methods:Flow cytometry was used to detect the expression of PD-1/PD-Ls on CD19⁺B-cells and CD19⁺CD20^+/-B-cells in peripheral blood of SLE patients and healthy controls?HCs?.The correlation between the expression of PD-1 signal pathway and clinical and laboratory parameters was analyzed.CD19⁺B-cells and CD19⁺CD20^+/-B-cells in peripheral blood of SLE patients and HCs were cultured by magnetic bead sorting technique.The expression of PD-1?PD-L1 and PD-L2 in CD19⁺B cells at different time points were detected under the stimulation of CpG or IFN-?.The proliferation of CD19⁺CD20⁺B-cells and CD19⁺CD20^-B-cells and the secretion of anti-double stranded DNA?ds-DNA?and immunoglobulin-G?IgG?at different time points were detected.The levels of soluble PD-1,PD-L1 and PD-L2 in plasma of SLE patients and HCs were detected by enzyme-linked immunosorbent assay?ELISA?,and the correlation between them and clinical and laboratory parameters was analyzed.Results:1.The expression levels of PD-1,PD-L1 and PD-L2 on the surface of CD19⁺B-cells in SLE patients were significantly higher than that in HCs;The frequency of CD19⁺PD-1^-PD-L1⁺B-cells and CD19⁺PD-L1⁺PD-L2^-B-cells in active SLE patient group was higher than that in the stable group and HCs,and was significantly correlated with some disease activity indexes.Under the stimulation of CPG or IFN-?,the expression frequency of PD-L1 and PD-L2 on the surface of CD19⁺B cells in SLE patients was significantly increased.The levels of soluble PD-L1 and PD-L2 in the plasma of SLE patients were higher than those in the HCs;the soluble PD-L1 in SLE active group was higher than the stable group,and the lupus nephritis group was higher than the non lupus nephritis group,and it was significantly correlated with SLEDAI score.2.The frequency of CD19⁺CD20^-B-cells in the active group was significantly higher than that in the stable group and the HCs.The expression levels of PD-1,PD-L1,PD-L2 and CD86 on the surface of CD19⁺CD20^-B-cells in SLE patients were significantly higher than those of CD19⁺CD20⁺B-cells,and were significantly related to some disease activity indexes.The secretion of ds-DNA and IgG of CD19⁺CD20^-B-cells in SLE patients is higher than that of CD19⁺CD20^+/-B-cells in HCs,and CD19⁺CD20^-B-cells in SLE patients have certain ability of division and proliferation.Conclusions:Our results showed that abnormal expression of PD-1/PD-Ls on peripheral blood B cells and abnormal levels of plasma soluble PD-L1 and upregulation of PD-L1 and PD-L2 on the surface of B cells stimulated by CPG or IFN-?all suggest possible related to the development and activity of SLE disease.The abnormal expression of peripheral blood CD20^-B-cells and their surface PD-1,PD-L1,PD-L2and CD86 in patients with SLE and the ability of CD20^-B-cells to proliferate and secrete autoantibodies all suggest that CD20^-B-cells may be activated B cells,and may be the reason for the poor efficacy of CD20 targeted therapy.