Patients with rheumatoid arthritis (RA) showed impaired immune tolerance characterized by reduced follicular regulatory T (Tfr) cells, and they also exhibited altered gut microbiotas and their metabolites in RA. However, the association of gut microbiotas and their metabolites with the immune tolerance mediated by Tfr cells in RA remains unclear. Peripheral blood and stool samples were collected from 32 new-onset RA patients and 17 healthy controls (HCs) in the Second Hospital of Shanxi Medical University between January 2022 and June 2022. The peripheral blood was used to detect the circulating regulatory T (Treg), helper T(Th)17, Tfr, and follicular helper T (Tfh) cells by modified flow cytometry. The stool samples were used to analyze the gut microbiotas and their metabolites via 16S rDNA sequencing and metabolomic profiling. We aimed to characterize the gut microbiotas and their metabolites in RA and identified their association with Tfr cell-mediated immune tolerance. The new-onset RA demonstrated reduced Treg and Tfr cells, associated with the disease activity and autoantibodies. There were significant differences in gut microbiotas between the two groups as the results of β diversity analysis (P = 0.039) including 21 differential gut microbiotas from the phylum to genus levels. In which, Ruminococcus 2 was associated with the disease activity and autoantibodies of RA, and it was identified as the potential biomarker of RA [area under curve (AUC) = 0.782, 95% confidence interval (CI) = 0.636–0.929, P = 0.001]. Eleven differential metabolites were identified and participated in four main pathways related to RA. Arachidonic acid might be the potential biomarker of RA (AUC = 0.724, 95% CI = 0.595–0.909, P = 0.038), and it was the core metabolite as the positive association with six gut microbiotas enriched in RA. The reduced Tfr cells were associated with the altered gut microbiotas and their metabolites including the Ruminococcus 2, the arachidonic acid involved in the biosynthesis of unsaturated fatty acid pathway and the 3-methyldioxyindole involved in the tryptophan metabolism pathway. The breakdown of immune tolerance mediated by reduced Tfr cells was associated with the altered gut microbiotas and their metabolites implying the possible mechanism of RA pathogenesis from the perspective of microecology-metabolism-immune.

中文翻译：

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类风湿性关节炎中 Tfr 细胞减少介导的免疫耐受受损与肠道菌群失调和代谢物改变有关

类风湿性关节炎 (RA) 患者表现出免疫耐受受损，其特征是滤泡调节性 T (Tfr) 细胞减少，并且他们在 RA 中也表现出肠道微生物群及其代谢物的改变。然而，肠道微生物群及其代谢物与 RA 中 Tfr 细胞介导的免疫耐受之间的关系仍不清楚。采集2022年1月至2022年6月山西医科大学第二医院32例新发RA患者和17例健康对照者的外周血和粪便样本。外周血用于检测循环调节性T（Treg） 、辅助 T(Th)17、Tfr 和滤泡辅助 T (Tfh) 细胞，采用改良流式细胞术检测。粪便样本用于通过 16S rDNA 测序和代谢组学分析来分析肠道微生物群及其代谢物。我们的目的是描述 RA 中肠道微生物群及其代谢物的特征，并确定它们与 Tfr 细胞介导的免疫耐受的关系。新发的 RA 表现出 Treg 和 Tfr 细胞减少，这与疾病活动性和自身抗体有关。β多样性分析结果显示，两组之间的肠道微生物群存在显着差异（P=0.039），包括从门到属水平的21个差异肠道微生物群。其中，瘤胃球菌2与RA的疾病活动性和自身抗体相关，被确定为RA的潜在生物标志物[曲线下面积（AUC）= 0.782，95%置信区间（CI）= 0.636-0.929，P = 0.001]。鉴定出 11 种差异代谢物，并参与与 RA 相关的 4 个主要途径。花生四烯酸可能是 RA 的潜在生物标志物（AUC = 0.724，95% CI = 0.595–0.909，P = 0.038），并且它是核心代谢物，与 RA 中富集的六种肠道菌群呈正相关。Tfr细胞减少与肠道微生物群及其代谢物的改变有关，包括瘤胃球菌2、参与不饱和脂肪酸途径生物合成的花生四烯酸和参与色氨酸代谢途径的3-甲基二氧吲哚。Tfr细胞减少介导的免疫耐受破坏与肠道菌群及其代谢物的改变有关，从微生态-代谢-免疫的角度暗示RA发病机制的可能机制。