Abstract: Objective To investigate the role of CD19⁺CD24hiCD38hi regulatory B (Breg) cells in the progression of rheumatoid arthritis (RA), the proportion and function of Breg cells were detected in the peripheral blood of RA patients. Methods Flow cytometry staining were used to detect the percentage of peripheral blood CD19⁺CD24^hiCD38^hi B cells and CD4 T cells from the healthy controls and RA patients;and the effects of CD19⁺CD24^hiCD38^hi B cells on the proliferative capacity of Nave CD4 T cells were detected by the live cell fluorescence dye CFSE labeling assay.The effects of CD19⁺CD24^hiCD38^hi B cells on the ability to secret IFN-γ of CD4 T cells and the ability to secret IL-10 of CD19⁺CD24^hiCD38^hi B cells were also be detected. Results The proportion of the CD19⁺CD24^hiCD38^hi B cells in the peripheral blood in RA patients was significantly decreased compared with the healthy group controls.However,the proportion of CD4 T cells in the RA patients was higher than those in healthy controls,and the differences were more significant with the progression of RA(P<0.05).Functional studies demonstrate that the ability to secret IL-10 of CD19⁺CD24^hiCD38^hi B cells was lower in the RA patients(P<0.01).Moreover,the ability to inhibit the proliferation and secretion capacity of Nave CD4 T cells was greatly decreased compared with healthy controls(P<0.01). Conclusion The ability to secrete IL-10 of CD19⁺CD24^hiCD38^hi B cells in the peripheral blood is reduced in the RA patients,leading to the impairment of the function of the immune suppression,and the increased proportion of CD4 T cells in the peripheral blood with the rised levels of IFN-γ,and accelerate the progression of RA patients.