[Detection of peripheral follicular helper T cells in rheumatoid arthritis]

To detect cell frequency and surface markers of peripheral CD4⁺CXCR5+ follicular helper T (Tfh) cells and analyze the correlation between CD4⁺CXCR5⁺Tfh cells and rheumatoid arthritis (RA) disease activity.

Forty RA patients meeting the American College of Rheumatology classification criteria for RA and twenty healthy controls (HC) were included. The peripheral blood mononuclear cells and sera were collected. The expressions of CD4+CXCR5⁺Tfh cells (CXCR5, C-X-C chemokine receptor type 5) and inducible T cell costimulator (ICOS), programmed death 1 positive (PD-1), interleukin-21 receptor (IL-21R) and CD40 ligand (CD40L) positive on CD4⁺CXCR5⁺Tfh cells were analyzed by flow cytometry. The transcript levels of B-cell lymphoma 6 (Bcl-6), as well as IL-21 and IL-21R, were measured by real-time polymerase chain reaction. Besides, serum IL-21 and CXCL13 concentrations were determined by enzyme-linked immunosorbent assay. The potential association between Tfh cells and RA disease activity was detected.

The cell surface marker of CXCR5⁺ on CD4⁺ cells was significantly increasingly higher across the following groups versus HC: total RA patients (16.75±3.92 vs.7.49±1.84, P<0.001); RA patients with low disease activity or remission (16.62±3.43 vs. 7.49±1.84, P<0.001); RA patients with moderate disease activity (16.82±3.07 vs. 7.49±1.84, P<0.001) and RA patients with high disease activity (16.87±5.50 vs. 7.49±1.84, P<0.001). Besides, the percentages of ICOS+, PD-1⁺, IL-21R⁺ on CD4⁺CXCR5⁺Tfh cells in the RA patients were significantly higher than that of HC (ICOS⁺CD4⁺CXCR5⁺cells, 8.37±4.28 vs. 3.72±1.81, P<0.001; PD-1⁺CD4⁺CXCR5⁺cells, 1.57±1.10 vs. 0.24±0.30, P=0.035; IL-21R⁺CD4⁺CXCR5⁺ cells, 4.60 ±4.05 vs. 0.20±0.19, P=0.006). But the percentage of CD40L⁺ on CXCR5⁺CD4⁺Tfh cells in the RA patients was not significantly higher than that of HC (3.38±3.71 vs. 0.54±0.34, P=0.135). The IL-21R mRNA expression was elevated significantly (5.00±4.94 vs. 0.74±0.55, P<0.001) in the RA patients but not in Bcl-6 mRNA[4.54(3.33, 7.23) vs. 5.31(2.81, 7.44), P=0.329]or IL-21 mRAN[0.72(0.26, 3.45) vs. 0.56(0.27, 3.71), P=0.195]. Additionally, the serum interleukin-21 (IL-21) and CXCL13 levels in the RA patients were higher than in the healthy controls [IL-21, (200.49±154.56) ng/L vs. (8.21±5.95) ng/L, P<0.001; CXCL13, (93.72±49.72) ng/L vs. (43.09±1.28) ng/L, P<0.001] and were both positively correlated with RA disease activity indexes, including erythrocyte sedimentation rate, the disease activity score in 28 joints (ESR-based or CRP-based), clinical disease activity index, and simplified disease activity index. However, none of the Tfh cells, anti-citrullinated protein antibody or rheumatoid factor had any relationship with RA disease activity.

Peripheral Tfh cells and their relevant cytokines are higher in RA patients than healthy controls, indicating Tfh cells may participate in the pathogenesis of RA, therefore, blocking the pathway of Tfh cells may be reasonable cellular targets for therapeutic intervention.