The colon is primarily responsible for absorbing fluids. It contains a large number of microorganisms including fungi, which are enriched in its distal segment. The colonic mucosa must therefore tightly regulate fluid influx to control absorption of fungal metabolites, which can be toxic to epithelial cells and lead to barrier dysfunction. How this is achieved remains unknown. Here, we describe a mechanism by which the innate immune system allows rapid quality check of absorbed fluids to avoid intoxication of colonocytes. This mechanism relies on a population of distal colon macrophages that are equipped with “balloon-like” protrusions (BLPs) inserted in the epithelium, which sample absorbed fluids. In the absence of macrophages or BLPs, epithelial cells keep absorbing fluids containing fungal products, leading to their death and subsequent loss of epithelial barrier integrity. These results reveal an unexpected and essential role of macrophages in the maintenance of colon-microbiota interactions in homeostasis.

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中文翻译：

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巨噬细胞通过限制真菌产物吸收来维持上皮完整性

结肠主要负责吸收液体。它含有大量微生物，包括真菌，在其远端部分富集。因此，结肠粘膜必须严格调节液体流入以控制真菌代谢物的吸收，真菌代谢物可能对上皮细胞有毒并导致屏障功能障碍。这是如何实现的仍然未知。在这里，我们描述了先天免疫系统允许对吸收的液体进行快速质量检查以避免结肠细胞中毒的机制。这种机制依赖于一群远端结肠巨噬细胞，这些巨噬细胞配备有插入上皮的“气球状”突起（BLP），对吸收的液体进行采样。在没有巨噬细胞或 BLP 的情况下，上皮细胞不断吸收含有真菌产物的液体，导致他们的死亡和随后的上皮屏障完整性丧失。这些结果揭示了巨噬细胞在维持体内平衡中结肠-微生物群相互作用中的意外和重要作用。

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