Imbalance of circulating Tfr/Tfh ratio in patients with rheumatoid arthritis

Follicular helper T(Tfh) cells and follicular regulatory T(Tfr) cells are critical for the development and maintenance of germinal center and humoral immune responses. Accumulating evidence has demonstrated that the dysregulation of either Tfh or Tfr cells contributes to the pathogenesis of autoimmune diseases. The aim of this study was to examine the numbers of Tfh and Tfr cells in patients with rheumatoid arthritis (RA). Twenty-four patients with RA patients and 20 health controls (HCs) were enrolled in this study. We analyzed the numbers of Tfh (CD4⁺ CXCR5⁺ PD-1^hi) cells and Tfr (CD4⁺ CXCR5⁺CD127^lo) cells in 24 RA patients via flow cytometry. The level of the soluble PD-1 and its ligands (sPD-L1 and sPDL-2) were examined by ELISA. Flow cytometry revealed that both circulating Tfh and Tfr cells were increased in RA patients compared with HCs. More importantly, the ratio of Tfr/Tfh was decreased, indicating a disruption of the balance between Tfh and Tfr. The Tfr/Tfh ratio was inversely correlated with level of serum CRP, ESR, RF, anti-CCP, IgG and DAS28 index. We also found that the serum level of sPD-1 was significantly elevated in the RA patients, which was positively correlated with CRP, ESR and the number of Tfh cells. These results indicate that an imbalance of circulating Tfr and Tfh cells may be involved in the immunopathogenesis of RA and may provide novel insight for the development of RA therapies.