[The proportion of CD19 + CD25 + Bregs in peripheral blood and the expression of PD-1 and PD-L1 on cell surface in patients with systemic lupus erythematosus and their correlation with clinical indicators].

Objective To investigate the expression and clinical significance of PD-1 and its ligand PD-L1 in peripheral blood CD19+ CD25+ regulatory B cells (Bregs) in patients with systemic lupus erythematosus (SLE). Methods Peripheral blood samples were collected from 50 patients and 41 healthy controls (HCs). The proportion of CD19+ CD25+ Bregs in peripheral blood as well as the expression of PD-1+ B and PD-L1+ B cells on CD19+ CD25+/- B cells, were detected by flow cytometry. At the same time, clinical information, such as clinical manifestations and laboratory indexes, was collected from patients. CD4+ T cells and CD19+ B cells were isolated by immunomagnetic beads and co-cultured in vitro to detect the differentiation of Bregs. Results The proportion of CD19+ CD25+ Bregs in the peripheral blood of SLE patients was lower than that in HC, while the expression of PD-1 and PD-L1 on Bregs was higher than that in HCs. SLE patients with pleural effusion, arthritis, and elevated CRP had a higher frequency of Bregs compared to the corresponding negative group. SLE patients with decreased immunoglobulin M (IgM) and positive anti-ribonuclear protein (RNP) antibodies had a lower frequency of Bregs compared to the corresponding negative group. SLE patients with infection, fever, arthritis, and elevated immunoglobulin A (IgA) had a higher frequency of CD19+ CD25+ PD-1+ cells compared to the corresponding negative group. SLE patients with infection, fever, and elevated IgA had a higher frequency of CD19+ CD25+ PD-L1+ cells compared to the corresponding negative group. And activated CD4+ T cells were beneficial to the expression of CD25 on CD19+ B cells. Conclusion The peripheral blood CD19+ CD25+ Bregs are decreased in SLE patients, while the expression of PD-1 and PD-L1 on cell surface is increased, which is correlated with clinical manifestations and laboratory parameters. Activation of CD4+ T cells promotes the differentiation of Bregs.