Follicular helper T cells in peripheral blood of patients with rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disease that is characterized by the presence of different autoantibodies such as rheumatoid factor (RF) and anti-citrullinated protein antibodies. CD4T cells expressing CXCR5, referred as follicular helper T cells (Tfh), collaborate with B cells to produce antibodies. Differential expression of CXCR3 and CCR6 within CD4⁺CXCR5⁺ T cells defines three mayor subsets: CXCR3⁺CCR6^- (Tfh1), CXCR3^-CCR6^- (Tfh2) and CXCR3^-CCR6⁺ (Tfh17). The aim of the study was to assess whether there is an association between the percentage of these cells and RA and whether there is a correlation with disease activity.

Twenty-four RA patients, 22 healthy controls (HC) and 16 undifferentiated arthritis (UA) patients were included. Percentage of CD4⁺CXCR5⁺ T cells and their subsets were analyzed by flow cytometry.

No differences were found in the percentages of CD4⁺CXCR5⁺ T cells in the comparison of RA vs HC or RA vs UA patients. Tfh1, Tfh2 and Tfh17 subsets showed no differences either. There was no correlation between CD4⁺CXCR5⁺T cells, Tfh1, Tfh2 and Tfh17, and Disease Activity Score in twenty-eight joints (DAS28) or erythrocyte sedimentation rate. Surprisingly, there was a positive correlation between Tfh17 cells and C-reactive protein. Finally, there was no correlation between CD4⁺CXCR5⁺ T cells, or their subsets, and anti-mutated citrullinated vimentin, or between the cells and RF.

There were no differences between the percentages of CD4⁺CXCR5⁺ T cells and their subsets in peripheral blood of RA patients and the percentages of cells in the control groups. This finding does not rule out a pathogenic role of these cells in the development and activity of RA.