T lymphocytes are key cellular components of the adaptive immune system and play a central role in cell-mediated immunity in vertebrates. Despite their heterogeneities, it is believed that all different types of T lymphocytes are generated exclusively via the differentiation of hematopoietic stem cells (HSCs). Using temporal–spatial resolved fate-mapping analysis and time-lapse imaging, here we show that the ventral endothelium in the zebrafish aorta–gonad–mesonephros and posterior blood island, the hematopoietic tissues previously known to generate HSCs and erythromyeloid progenitors, respectively, gives rise to a transient wave of T lymphopoiesis independent of HSCs. This HSC-independent T lymphopoiesis occurs early and generates predominantly CD4 T_αβ cells in the larval but not juvenile and adult stages, whereas HSC-dependent T lymphopoiesis emerges late and produces various subtypes of T lymphocytes continuously from the larval stage to adulthood. Our study unveils the existence, origin, and ontogeny of HSC-independent T lymphopoiesis in vivo and reveals the complexity of the endothelial-hematopoietic transition of the aorta.

T淋巴细胞是适应性免疫系统的关键细胞成分，在脊椎动物的细胞介导的免疫中起着核心作用。尽管它们具有异质性，但据信所有不同类型的T淋巴细胞仅通过造血干细胞（HSC）的分化而产生。使用时空分辨的命运映射分析和延时成像，我们发现斑马鱼主动脉-性腺-中肾和后血岛的腹膜内皮，先前已知分别产生HSC和红血球祖细胞的造血组织引起独立于HSC的T淋巴细胞生成的短暂性波动。这种非HSC依赖性T淋巴细胞生成较早发生，并主要产生CD4 _Tαβ在幼虫阶段，但不是幼稚阶段和成年阶段，这些细胞会发育成熟，而HSC依赖的T淋巴细胞则出现得较晚，并从幼虫阶段到成年期不断产生各种亚型的T淋巴细胞。我们的研究揭示了体内HSC非依赖性T淋巴细胞生成的存在，起源和个体发育，并揭示了主动脉内皮-造血过渡的复杂性。