Macrophages are diverse immune cells that reside in all tissues. Although macrophages have been implicated in mammary-gland function, their diversity has not been fully addressed. By exploiting high-resolution three-dimensional imaging and flow cytometry, we identified a unique population of tissue-resident ductal macrophages that form a contiguous network between the luminal and basal layers of the epithelial tree throughout postnatal development. Ductal macrophages are long lived and constantly survey the epithelium through dendrite movement, revealed via advanced intravital imaging. Although initially originating from embryonic precursors, ductal macrophages derive from circulating monocytes as they expand during puberty. Moreover, they undergo proliferation in pregnancy to maintain complete coverage of the epithelium in lactation, when they are poised to phagocytose milk-producing cells post-lactation and facilitate remodelling. Interestingly, ductal macrophages strongly resemble mammary tumour macrophages and form a network that pervades the tumour. Thus, the mammary epithelium programs specialized resident macrophages in both physiological and tumorigenic contexts.

中文翻译：

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组织驻留的导管巨噬细胞检查乳腺上皮并促进组织重塑。

巨噬细胞是驻留在所有组织中的多种免疫细胞。尽管巨噬细胞与乳腺功能有关，但其多样性尚未得到充分解决。通过利用高分辨率三维成像和流式细胞仪，我们确定了独特的组织驻留导管巨噬细胞种群，这些种群在整个产后发育过程中在上皮树的腔层和基底层之间形成了连续的网络。导管巨噬细胞寿命长，并通过树突运动不断观察上皮，并通过先进的活体成像显露。尽管导管巨噬细胞最初起源于胚胎前体，但它们在青春期扩张时仍来自循环单核细胞。此外，它们在怀孕期间会发生增殖，以保持泌乳时上皮的完全覆盖，当它们准备好在哺乳后吞噬产乳细胞并促进重塑时。有趣的是，导管巨噬细胞非常类似于乳腺肿瘤巨噬细胞，并形成遍布肿瘤的网络。因此，乳腺上皮程序在生理和致瘤性方面都使驻留的巨噬细胞专门化。