Supplementary file 3_Heterogeneity and longitudinal transcriptomic characteristics of Tregs in COVID-19 patients.pdf

IntroductionRegulatory T cells (Tregs) play a crucial role in maintaining immune tolerance by suppressing immune responses against pathogens. The fluctuation of Treg proportions in COVID-19 remains a topic of debate, and the mechanisms triggering Treg activation in COVID-19 are still unclear. Understanding these issues is essential for better managing immune responses in COVID-19 patients.
MethodsWe collected a cohort of COVID-19 patients with varying disease severity and stage to explore the transcriptomic and functional traits of Tregs in these individuals. Using transcriptomic analysis, we evaluated the proportion and functionality of different Treg subsets, specifically HLA_DR+ Tregs, across different stages of COVID-19 patients.
ResultsOur analysis revealed that the proportion of CCR7+ Tregs decreased as the disease advanced, while the cell proportion of HLA_DR+ regs escalated with the severity of the disease. Moreover, the transcription actor CARHSP1 exhibited apositive correlation with the proportion of HLA_DR+ Tregs. Notably, the heightened suppressive function of HLA_DR+ Tregs in severe COVID-19 patients, with interactions between PF4 and CXCR3, contributed to the homeostasis of HLA_DR+ Tregs in severe COVID-19 patients. Furthermore, we observed that Tregs in COVID-19 patients exhibited weakened TCR clonotype expansion, and the suppression of HLA_DR+ Tregs with expanded TCR clonotypes in severe COVID-19 cases did not show a significant increase compared to asymptomatic and mild COVID-19 groups. The findings indicate that Tregs may be activated through the bystander effect, as evidenced by the analysis of TCR clonotype characteristics.
DiscussionOur research delineates the diversity of dynamic alterations in Tregs and sheds light on potential mechanisms underlying Treg activation, providing a theoretical foundation and offering treatment strategies for managing COVID-19 patients.

引言：调节性T细胞（Regulatory T cells, Tregs）通过抑制针对病原体的免疫应答，在维持机体免疫耐受中发挥核心作用。当前，COVID-19患者体内Treg比例的波动仍存在学术争议，而COVID-19情境下触发Treg活化的具体机制尚未阐明。厘清上述科学问题，对于优化COVID-19患者的免疫应答管理具有重要意义。

方法：本研究纳入一组疾病严重程度与病程阶段各异的COVID-19患者队列，旨在探究此类人群中Treg的转录组学特征与功能表型。通过转录组学分析，我们系统评估了不同病程阶段的COVID-19患者体内不同Treg亚群（尤其是HLA-DR阳性Treg，HLA_DR+ Tregs）的比例与功能活性。

结果：本研究分析结果显示，随着疾病进展，CCR7阳性Treg（CCR7+ Tregs）的比例逐渐下降；而HLA-DR阳性Treg的比例则随疾病严重程度升高而显著上升。此外，转录因子CARHSP1的表达水平与HLA-DR阳性Treg的比例呈正相关。值得注意的是，重症COVID-19患者体内HLA-DR阳性Treg的免疫抑制功能显著增强，且PF4与CXCR3的相互作用参与维持了此类患者体内HLA-DR阳性Treg的稳态。进一步研究发现，COVID-19患者体内的Treg呈现出TCR克隆型（TCR clonotype）扩增减弱的特征；与无症状及轻症COVID-19患者组相比，重症患者体内携带扩增TCR克隆型的HLA-DR阳性Treg的免疫抑制功能并未出现显著提升。通过TCR克隆型特征分析结果可证实，Treg或可通过旁观者效应完成活化。

讨论：本研究阐明了Treg动态变化的多样性，揭示了Treg活化的潜在分子机制，为COVID-19患者的临床管理提供了理论依据与潜在治疗策略。