CCR4 和 CCR7 差异调节胸腺细胞定位,对中枢耐受产生不同结果。
CCR4 and CCR7 differentially regulate thymocyte localization with distinct outcomes for central tolerance.
机构信息
Department of Molecular Biosciences, The University of Texas at Austin, Austin, United States.
Department of Pathology, Duke University, Durham, United States.
出版信息
Elife. 2023 Jun 2;12:e80443. doi: 10.7554/eLife.80443.
Central tolerance ensures autoreactive T cells are eliminated or diverted to the regulatory T cell lineage, thus preventing autoimmunity. To undergo central tolerance, thymocytes must enter the medulla to test their T-cell receptors (TCRs) for autoreactivity against the diverse self-antigens displayed by antigen-presenting cells (APCs). While CCR7 is known to promote thymocyte medullary entry and negative selection, our previous studies implicate CCR4 in these processes, raising the question of whether CCR4 and CCR7 play distinct or redundant roles in central tolerance. Here, synchronized positive selection assays, two-photon time-lapse microscopy, and quantification of TCR-signaled apoptotic thymocytes, demonstrate that CCR4 and CCR7 promote medullary accumulation and central tolerance of distinct post-positive selection thymocyte subsets in mice. CCR4 is upregulated within hours of positive selection signaling and promotes medullary entry and clonal deletion of immature post-positive selection thymocytes. In contrast, CCR7 is expressed several days later and is required for medullary localization and negative selection of mature thymocytes. In addition, CCR4 and CCR7 differentially enforce self-tolerance, with CCR4 enforcing tolerance to self-antigens presented by activated APCs, which express CCR4 ligands. Our findings show that CCR7 expression is not synonymous with medullary localization and support a revised model of central tolerance in which CCR4 and CCR7 promote early and late stages of negative selection, respectively, via interactions with distinct APC subsets.
中枢耐受确保自身反应性 T 细胞被消除或转向调节性 T 细胞谱系,从而防止自身免疫。为了经历中枢耐受,胸腺细胞必须进入髓质,以测试其 T 细胞受体(TCR)对由抗原呈递细胞(APC)展示的各种自身抗原的自身反应性。虽然已知 CCR7 可促进胸腺细胞向髓质的进入和阴性选择,但我们之前的研究表明 CCR4 也参与了这些过程,这就提出了一个问题,即 CCR4 和 CCR7 是否在中枢耐受中发挥独特或冗余的作用。在这里,同步正选择测定、双光子延时显微镜和 TCR 信号诱导的凋亡胸腺细胞的定量分析表明,CCR4 和 CCR7 促进了不同正选择后胸腺细胞亚群在小鼠中的髓质积累和中枢耐受。CCR4 在正选择信号发生后的数小时内被上调,并促进不成熟的正选择后胸腺细胞的髓质进入和克隆性删除。相比之下,CCR7 表达数天后才出现,是成熟胸腺细胞在髓质定位和阴性选择所必需的。此外,CCR4 和 CCR7 以不同的方式执行自身耐受,CCR4 对表达 CCR4 配体的激活 APC 所呈现的自身抗原执行耐受。我们的研究结果表明,CCR7 表达并不等同于髓质定位,并支持一个经过修订的中枢耐受模型,其中 CCR4 和 CCR7 通过与不同的 APC 亚群相互作用,分别促进阴性选择的早期和晚期阶段。