The use of adult Drosophila melanogaster as a model for hematopoiesis or organismal immunity has been debated. Addressing this question, we identify an extensive reservoir of blood cells (hemocytes) at the respiratory epithelia (tracheal air sacs) of the thorax and head. Lineage tracing and functional analyses demonstrate that the majority of adult hemocytes are phagocytic macrophages (plasmatocytes) from the embryonic lineage that parallels vertebrate tissue macrophages. Surprisingly, we find no sign of adult hemocyte expansion. Instead, hemocytes play a role in relaying an innate immune response to the blood cell reservoir: through Imd signaling and the Jak/Stat pathway ligand Upd3, hemocytes act as sentinels of bacterial infection, inducing expression of the antimicrobial peptide Drosocin in respiratory epithelia and colocalizing fat body domains. Drosocin expression in turn promotes animal survival after infection. Our work identifies a multi-signal relay of organismal humoral immunity, establishing adult Drosophila as model for inter-organ immunity.

中文翻译：

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成年果蝇缺乏造血功能，但依靠呼吸上皮细胞的血细胞库将感染信号传递给周围组织。

使用成年黑腹果蝇作为造血或机体免疫的模型一直存在争议。为了解决这个问题，我们在胸部和头部的呼吸上皮（气管气囊）中发现了大量的血细胞（血细胞）。谱系追踪和功能分析表明，大多数成人血细胞是来自与脊椎动物组织巨噬细胞平行的胚胎谱系的吞噬巨噬细胞（浆细胞）。令人惊讶的是，我们没有发现成人血细胞扩张的迹象。相反，血细胞在将先天免疫反应传递到血细胞库中发挥作用：通过 Imd 信号传导和 Jak/Stat 通路配体 Upd3，血细胞充当细菌感染的哨兵，诱导抗菌肽 Drosocin 在呼吸道上皮细胞和共定位脂肪体结构域中的表达。Drosocin 的表达反过来促进感染后的动物存活。我们的工作确定了有机体体液免疫的多信号中继，建立了成年果蝇作为器官间免疫的模型。