Transcriptional basis of mouse and human dendritic cell heterogeneity revealed by single-cell profiling

Dendritic cells (DCs) play a critical role in orchestrating adaptive immune responses due to their unique ability to serve as a principal antigen-presenting cell type capable of initiating T cell responses. Classical dendritic cells have been divided into two subsets, cDC1 and cDC2, based on phenotypic markers and their distinct abilities to prime CD8 and CD4 T cells and direct their differentiation into effectors. Whilst the transcriptional features of the cDC1 subset have been well characterized, the heterogeneity of cDC2 and the development and function of distinct cell types comprising this subset remain poorly understood. Unbiased single-cell RNA sequencing analysis of DCs, combined with genetic reporter expression and fate-mapping revealed two principal cDC2 lineages, their developmental pathways and transcriptional regulators, including the expression of T-bet and RORgammat, two key transcription factors known to define functional adaptive and innate lymphocyte subsets. The cDC2 lineages were characterized by distinct metabolic and functional programs with phenotypic conservation observed across tissues. Extending the findings in mice to humans revealed conserved characteristics of DC heterogeneity and the presence of the newly defined DC subsets in human autoimmune disease and cancer. Single-cell RNA sequencing was performed on mouse and human splenic dendritic cells. Two samples of mouse dendritic cells were FACS purified based on Tbx21Cre-RFP reporter expression. Single-cell RNA sequencing was also performed on CD45-positive cells in melanoma tumors from two patients.树突状细胞（dendritic cells, DCs）作为一类可启动T细胞应答的核心抗原呈递细胞，凭借其独特能力在统筹适应性免疫应答过程中发挥关键作用。经典树突状细胞可分为cDC1与cDC2两个亚群，二者基于表型标志物、激活CD8及CD4 T细胞的能力差异，以及引导其分化为效应细胞的功能特征而区分。尽管cDC1亚群的转录特征已得到充分阐释，但cDC2的异质性，以及该亚群内不同细胞类群的发育与功能，目前仍有待深入解析。对树突状细胞开展无偏单细胞RNA测序，并结合遗传报告基因表达与命运图谱分析，研究人员揭示了两类主要的cDC2细胞谱系、其发育通路与转录调控因子，其中包括T-bet与RORγt的表达——这两种关键转录因子已被证实可定义功能性适应性与先天淋巴细胞亚群。这两类cDC2细胞谱系具有独特的代谢与功能程序，且在不同组织中均表现出表型保守性。将小鼠中的研究发现推广至人类后，研究人员观察到树突状细胞异质性的保守特征，以及新定义的树突状细胞亚群在人类自身免疫性疾病与癌症中的存在。研究团队对小鼠与人类脾脏树突状细胞开展了单细胞RNA测序。两份小鼠树突状细胞样本基于Tbx21Cre-RFP报告基因表达，通过荧光激活细胞分选（fluorescence-activated cell sorting, FACS）完成纯化。研究同时对两名患者黑色素瘤组织中的CD45阳性细胞开展了单细胞RNA测序。