Department of Neurology, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, China.
Brain Research Center, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, China.
CNS Neurosci Ther. 2024 Mar;30(3):e14682. doi: 10.1111/cns.14682.
Accumulating evidence supports the involvement of adaptive immunity in the development of radiation-induced brain injury (RIBI). Our previous work has emphasized the cytotoxic function of CD8 T cells in RIBI. In this study, we aimed to investigate the presence and potential roles of cytotoxic CD4 T cells (CD4 CTLs) in RIBI to gain a more comprehensive understanding of adaptive immunity in this context.
Utilizing single-cell RNA sequencing (scRNA-seq), we analyzed 3934 CD4 T cells from the brain lesions of four RIBI patients and identified six subclusters within this population. A notable subset, the cytotoxic CD4 T cells (CD4 CTLs), was marked with high expression of cytotoxicity-related genes (NKG7, GZMH, GNLY, FGFBP2, and GZMB) and several chemokine and chemokine receptors (CCL5, CX3CR1, and CCL4L2). Through in-depth pseudotime analysis, which simulates the development of CD4 T cells, we observed that the CD4 CTLs exhibited signatures of terminal differentiation. Their functions were enriched in protein serine/threonine kinase activity, GTPase regulator activity, phosphoprotein phosphatase activity, and cysteine-type endopeptidase activity involved in the apoptotic signaling pathway. Correspondingly, mice subjected to gamma knife irradiation on the brain showed a time-dependent infiltration of CD4 T cells, an increase of MHCII cells, and the existence of CD4 CTLs in lesions, along with an elevation of apoptotic-related proteins. Finally, and most crucially, single-cell T-cell receptor sequencing (scTCR-seq) analysis at the patient level determined a large clonal expansion of CD4 CTLs in lesion tissues of RIBI. Transcriptional factor-encoding genes TBX21, RORB, and EOMES showed positive correlations with the cytotoxic functions of CD4 T cells, suggesting their potential to distinguish RIBI-related CD4 CTLs from other subsets.
The present study enriches the understanding of the transcriptional landscape of adaptive immune cells in RIBI patients. It provides the first description of a clonally expanded CD4 CTL subset in RIBI lesions, which may illuminate new mechanisms in the development of RIBI and offer potential biomarkers or therapeutic targets for the disease.
越来越多的证据表明适应性免疫参与了放射性脑损伤（RIBI）的发生发展。我们之前的工作强调了 CD8 T 细胞在 RIBI 中的细胞毒性作用。在这项研究中，我们旨在研究 RIBI 中细胞毒性 CD4 T 细胞（CD4 CTLs）的存在和潜在作用，以更全面地了解适应性免疫在此背景下的作用。
我们利用单细胞 RNA 测序（scRNA-seq）分析了 4 名 RIBI 患者脑损伤中的 3934 个 CD4 T 细胞，在该群体中鉴定出 6 个亚群。一个值得注意的亚群，细胞毒性 CD4 T 细胞（CD4 CTLs），其特征是细胞毒性相关基因（NKG7、GZMH、GNLY、FGFBP2 和 GZMB）和几种趋化因子和趋化因子受体（CCL5、CX3CR1 和 CCL4L2）的高表达。通过模拟 CD4 T 细胞发育的深度拟时分析，我们观察到 CD4 CTLs 表现出终末分化的特征。它们的功能富集于丝氨酸/苏氨酸蛋白激酶活性、GTPase 调节活性、磷酸蛋白磷酸酶活性和胱天蛋白酶型内肽酶活性，这些功能涉及凋亡信号通路。相应地，在脑部接受伽玛刀照射的小鼠表现出时间依赖性的 CD4 T 细胞浸润、MHCII 细胞增加以及病变中 CD4 CTLs 的存在，同时凋亡相关蛋白升高。最后，也是最重要的是，在患者水平进行的单细胞 T 细胞受体测序（scTCR-seq）分析确定了 RIBI 病变组织中 CD4 CTLs 的大量克隆扩增。转录因子编码基因 TBX21、RORB 和 EOMES 与 CD4 T 细胞的细胞毒性功能呈正相关，这表明它们有可能将 RIBI 相关的 CD4 CTLs 与其他亚群区分开来。
本研究丰富了对 RIBI 患者适应性免疫细胞转录谱的认识。它首次描述了 RIBI 病变中克隆扩增的 CD4 CTL 亚群，这可能阐明了 RIBI 发展的新机制，并为该疾病提供了潜在的生物标志物或治疗靶点。
