Macrophages are an integral part of all organs in the body, where they contribute to immune surveillance, protection, and tissue-specific homeostatic functions. This is facilitated by so-called niches composed of macrophages and their surrounding stroma. These niches structurally anchor macrophages and provide them with survival factors and tissue-specific signals that imprint their functional identity. In turn, macrophages ensure appropriate functioning of the niches they reside in. Macrophages thus form reciprocal, mutually beneficial circuits with their cellular niches. In this review, we explore how this concept applies to the spleen, a large secondary lymphoid organ whose primary functions are to filter the blood and regulate immunity. We first outline the splenic micro-anatomy, the different populations of splenic fibroblasts and macrophages and their respective contribution to protection of and key physiological processes occurring in the spleen. We then discuss firmly established and potential cellular circuits formed by splenic macrophages and fibroblasts, with an emphasis on the molecular cues underlying their crosstalk and their relevance to splenic functionality. Lastly, we conclude by considering how these macrophage-fibroblast circuits might be impaired by aging, and how understanding these changes might help identify novel therapeutic avenues with the potential of restoring splenic functions in the elderly.

中文翻译：

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脾脏中的巨噬细胞-成纤维细胞回路

巨噬细胞是身体所有器官的组成部分，它们有助于免疫监视、保护和组织特异性稳态功能。这是由巨噬细胞及其周围基质组成的所谓壁龛促进的。这些壁龛在结构上锚定巨噬细胞，并为它们提供生存因子和组织特异性信号，以印记它们的功能特性。反过来，巨噬细胞确保它们所在的壁龛的适当功能。巨噬细胞因此与它们的细胞壁龛形成互惠互利的回路。在这篇综述中，我们探讨了这个概念如何应用于脾脏，这是一个大型的次级淋巴器官，其主要功能是过滤血液和调节免疫。我们首先概述脾的显微解剖结构，脾成纤维细胞和巨噬细胞的不同种群及其各自对保护脾脏中发生的关键生理过程的贡献。然后，我们讨论了由脾巨噬细胞和成纤维细胞形成的牢固建立和潜在的细胞回路，重点是它们的串扰背后的分子线索及其与脾功能的相关性。最后，我们通过考虑这些巨噬细胞 - 成纤维细胞回路如何因衰老而受损，以及了解这些变化如何有助于确定具有恢复老年人脾功能潜力的新治疗途径作为结论。然后，我们讨论了由脾巨噬细胞和成纤维细胞形成的牢固建立和潜在的细胞回路，重点是它们的串扰背后的分子线索及其与脾功能的相关性。最后，我们通过考虑这些巨噬细胞 - 成纤维细胞回路如何因衰老而受损，以及了解这些变化如何有助于确定具有恢复老年人脾功能潜力的新治疗途径作为结论。然后，我们讨论了由脾巨噬细胞和成纤维细胞形成的牢固建立和潜在的细胞回路，重点是它们的串扰背后的分子线索及其与脾功能的相关性。最后，我们通过考虑这些巨噬细胞 - 成纤维细胞回路如何因衰老而受损，以及了解这些变化如何有助于确定具有恢复老年人脾功能潜力的新治疗途径作为结论。