Background

Follicular helper T (Tfh) cells are a subgroup of activated CD4⁺ T cells which can assist the formation and maintenance of germinal centers. Follicular regulatory T (Tfr) cells are a new class of regulatory T cells which play a major role in suppressing cells in humoral immunity. In contrast to the role of Tfh cells, Tfr cells can inhibit the function of Tfh cells and B cells. Imbalance of blood Tfr/Tfh ratio resulted in the expansion of auto-reactive B cells and auto-antibody production (). However, the effect of Tfr cells and Tfh cells in the pathogenesis of RA (rheumatoid arthritis) is unclear. The purpose of this study was to investigate the function of Tfr cells and Tfh cells in the pathogenesis of RA.

Methods

We recruited 20 patients fulfilled the the American College of Rheumatology diagnosis criteria and 20 healthy controls (HCs). The number of CD4⁺CXCR5⁺Foxp3⁺ Tfr cells and CD4⁺CXCR5⁺ Tfh cells in 20 RA patients were measured by flow cytometry analysis. Furthermore, the correlations between the Tfr/Tfh ratio and the characteristic clinical parameters were assessed. The serum levels of IL-21(interleukin-21), CXCL13 (chemokine (C-X-C motif) ligand 13) and TGF-β (Transforming growth factor-β) were measured by ELISA. The formation of ectopic germinal center (GC) of synovial membrane was examined by H&E staining. The transcriptional levels of CXCR5 (C-X-C chemokine receptor type 5), CXCL13, ICOS (inducible co-stimulater) and TGF-β mRNA were also analyzed. In addition, the expression of Bcl-6 (B-cell lymphoma 6), CXCR5, CXCL13 and ICOS in synovial membrane were examined by immunohistochemistry.

Results

RA patients had more Tfh cells in peripheral blood, conversely, the frequency of blood Tfr cells (p < 0.05) and the ratio of Tfr/Tfh were significantly decreased compared to healthy controls (p < 0.05, p < 0.01). Furthermore, the ratio of Tfr/Tfh was negatively correlated with values of ESR (r=-0.57, p < 0.05), RF (r=-0.5275, p < 0.001), CRP (r=-0.4486, p < 0.001), IgG (r=-0.4631, p < 0.05), DAS28 scores (r=-0.5645, p < 0.01), as well as the levels of IL-21(r=-0.7398, p < 0.01), CXCL13 (r=-0.4832, p < 0.05). However, the ratio of Tfr/Tfh was positively with the serum level of TGF-β (r=0.5115, p < 0.05). Higher mRNA expression of CXCR5, CXCL13, ICOS and lower TGF-β mRNA expression were observed in RA patients. The serum expression level of IL-21, CXCL13 was significantly increased and expression of TGF-β was significantly decreased in RA patients. Furthermore, ectopic germinal center formation and higher expression of Bcl-6, CXCR5, ICOS, CXCL13 in the synovial membrane of the joints in RA patients were observed.

Conclusions

The decreased blood CD4⁺CXCR5⁺Foxp3⁺ Tfr cells/CD4⁺CXCR5⁺ Tfh

cells may be responsible for the immunopathogenesis of RA.

中文翻译：

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血液CD4 + CXCR5 + Foxp3 + Tfr细胞与CD4 + CXCR5 + Tfh细胞之间的失衡可能是类风湿关节炎的免疫发病机制。

背景

滤泡辅助性T（Tfh）细胞是活化的CD4 ⁺ T细胞的一个亚组，可协助生发中心的形成和维持。卵泡调节性T（Tfr）细胞是一类新的调节性T细胞，在抑制细胞的体液免疫中起主要作用。与Tfh细胞的作用相反，Tfr细胞可以抑制Tfh细胞和B细胞的功能。血液Tfr / Tfh比值的失衡导致自身反应性B细胞扩增和自身抗体产生（）。但是，尚不清楚Tfr细胞和Tfh细胞在RA（类风湿关节炎）发病机理中的作用。这项研究的目的是研究Tfr细胞和Tfh细胞在RA发病中的功能。

方法

我们招募了20位符合美国风湿病学会诊断标准的患者和20位健康对照（HCs）。CD4 ⁺ CXCR5 ⁺ Foxp3 ⁺ Tfr细胞和CD4 ⁺ CXCR5 ^+的数量通过流式细胞术分析测量了20例RA患者的Tfh细胞。此外，评估了Tfr / Tfh比值与特征性临床参数之间的相关性。通过ELISA测定血清IL-21（白介素21），CXCL13（趋化因子（CXC基序）配体13）和TGF-β（转化生长因子-β）的水平。通过H＆E染色检查滑膜异位生发中心（GC）的形成。还分析了CXCR5（5型CXC趋化因子受体），CXCL13，ICOS（诱导型共刺激物）和TGF-βmRNA的转录水平。此外，通过免疫组织化学检查滑膜中Bcl-6（B细胞淋巴瘤6），CXCR5，CXCL13和ICOS的表达。

结果

RA患者外周血中的Tfh细胞更多，相反，与健康对照组相比，血Tfr细胞的频率（p <0.05）和Tfr / Tfh的比率显着降低（p <0.05，p <0.01）。此外，Tfr / Tfh的比率与ESR（r = -0.57，p <0.05），RF（r = -0.5275，p <0.001），CRP（r = -0.4486，p <0.001）， IgG（r = -0.4631，p <0.05），DAS28得分（r = -0.5645，p <0.01），以及IL-21的水平（r = -0.7398，p <0.01），CXCL13（r =- 0.4832，页<0.05）。然而，Tfr / Tfh的比率与血清TGF-β的水平呈正相关（r = 0.5115，p <0.05）。RA患者中CXCR5，CXCL13，ICOS的mRNA表达较高，而TGF-β的mRNA表达较低。RA患者血清中IL-21，CXCL13的表达水平明显升高，而TGF-β的表达则明显降低。此外，在RA患者的关节滑膜中观察到异位生发中心的形成和Bcl-6，CXCR5，ICOS，CXCL13的高表达。

结论

减少的血液CD4 ⁺ CXCR5 ⁺ Foxp3 ⁺ Tfr细胞/ CD4 ⁺ CXCR5 ⁺ Tfh

细胞可能是RA的免疫发病机制的原因。