The human immune system is made up of a huge variety of cell types each with unique functions. Local networks of resident immune cells are poised to sense and protect against pathogen entry, whereas more widespread innate and adaptive immune networks provide first rapid, then long-lasting and targeted responses. However, how we develop such a diverse and complex system remains unknown. Studying human development directly has been challenging in the past, but recent advances in single-cell and spatial genomics, together with the co-ordinated efforts of the Human Cell Atlas and other initiatives, have led to new studies that map the development of the human immune system in unprecedented detail. In this Review, we consider the timings, transitions, cell types and tissue microenvironments that are crucial for building the human immune system. We also compare and contrast the human system with model species and in vitro systems, and discuss how an understanding of prenatal immune system development will improve our knowledge of human disease.

人体免疫系统由多种细胞类型组成，每种细胞类型都有独特的功能。常驻免疫细胞的局部网络随时准备感知和防止病原体进入，而更广泛的先天性和适应性免疫网络首先提供快速、持久和有针对性的反应。然而，我们如何开发这样一个多样化和复杂的系统仍然未知。过去，直接研究人类发育一直具有挑战性，但单细胞和空间基因组学的最新进展，以及人类细胞图谱和其他倡议的协调努力，导致了新的研究，以前所未有的细节绘制了人类免疫系统的发育图谱。在这篇综述中，我们考虑了对构建人类免疫系统至关重要的时间、转变、细胞类型和组织微环境。我们还将人体系统与模型物种和体外系统进行比较和对比，并讨论对产前免疫系统发育的理解将如何提高我们对人类疾病的了解。