Evolution and selection have shaped diverse immune systems throughout phylogeny, the vast majority of which remain unexplored. Botryllus schlosseri is a colonial tunicate, a sister group to vertebrates, that develops as a chordate, then metamorphoses to an asexually reproductive invertebrate that every week makes the same body plan from budded stem cells. Genetically distinct B. schlosseri colonies can fuse to form a chimera, or reject each other based on allogeneic recognition. In chimeras, circulating germline and somatic stem cells participate in development; stem cells compete in all individuals in the fused colonies, with rejection preventing germline parasitism. Here we review the isolation and characterization of B. schlosseri hematopoietic stem cells (HSC) and their niches, and the role of the immune effector cells in allorecognition.

中文翻译：

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通过殖民脊索动物对造血系统的进化观点：同种异体免疫和造血。

进化和选择在整个系统发育过程中塑造了不同的免疫系统，其中绝大多数仍未被探索。Botryllus schlosseri 是一种殖民地被囊动物，是脊椎动物的姊妹群，发育为脊索动物，然后变态为无性繁殖的无脊椎动物，每周都用出芽的干细胞制作相同的身体计划。遗传上不同的 B. schlosseri 菌落可以融合形成嵌合体，或基于同种异体识别相互排斥。在嵌合体中，循环生殖系和体干细胞参与发育；干细胞在融合集落中的所有个体中竞争，排斥防止生殖系寄生。在这里，我们回顾了 B. schlosseri 造血干细胞 (HSC) 及其壁龛的分离和表征，以及免疫效应细胞在同种异体识别中的作用。