Changes in regulatory B cells and their relationship with rheumatoid arthritis disease activity

Regulatory subsets of B cells (Bregs) modulate immune responses in autoimmunity, cancer, and other inflammation diseases. In the present study, we investigated the numbers of circulating Breg cells in patients with rheumatoid arthritis (RA). We evaluated 59 RA patients and 25 healthy controls. CD19⁺CD5⁺CD1d^hi B cells and granzyme B-secreting B cells (CD19⁺CD5⁺GzmB⁺) were analyzed by flow cytometry in peripheral blood mononuclear cells. We detected serum interleukin 10 (IL-10), interleukin 21 (IL-21), granzyme B (GzmB) using enzyme-linked immunosorbent assay (ELISA). Compared to control subjects, we found a decreased proportion of CD19⁺CD5⁺CD1d^hi B cells in RA patients. The number of CD19⁺CD5⁺CD1d^hi B cells negatively correlated with DAS28 (P < 0.05). Moreover, serum IL-10 and IL-21 concentrations were significantly lower in RA patients compared to healthy controls (P < 0.05). Conversely, the number of CD19⁺CD5⁺GzmB⁺ B cells was significantly higher in RA patients (P < 0.05), and the number of CD19⁺CD5⁺GzmB⁺ B cells did not correlate with DAS28, IL-21, or GzmB (P > 0.05, all). Interestingly, IL-21 and GzmB levels positively correlated in RA patients (P < 0.05). Our data indicate that CD19⁺CD5⁺CD1d^hi B cells influence RA disease activity. CD19⁺CD5⁺GzmB⁺ B cells may be involved in RA development and progression. Our data strongly suggest a role for Bregs in RA, and Bregs may be a viable therapeutic strategy for RA disease.