Dendritic cells (DCs) are the sentinels of the immune system, sensing a diverse array of pathogens to stimulate a robust and appropriate immune response. To initiate responses to highly disparate challenges, DCs have diversified into multiple phenotypically, anatomically, and functionally distinct cell types. As a result of the application of new single-cell technologies, the full extent of this diversity, as well as the developmental relationships of the DC lineages, is currently undergoing reassessment. Here, we review the cellular and molecular evidence that underpins current models of DC differentiation and functional diversification in the murine and human systems. We discuss these models in the context of the diversity revealed by single-cell studies and propose that understanding DC identity will require defining the regulatory interactions that control gene expression in these cells.

树突状细胞（DC）是免疫系统的前哨，可感应多种病原体，以刺激强大而适当的免疫反应。为了启动对高度不同挑战的响应，DC已分化为多种表型，解剖学和功能不同的细胞类型。由于应用了新的单细胞技术，目前正在对这种多样性的全部范围以及DC血统的发展关系进行重新评估。在这里，我们审查了支持小鼠和人类系统中DC分化和功能多样化的当前模型的细胞和分子证据。