Endotoxin tolerance is an important state for the prevention of lethal infection and inflammatory response, which is closely associated with the participation of innate immune cells. Moreover, mesenteric lymph nodes (MLNs)-resident immune cells, such as CD4⁺Foxp3⁺ regulatory T (Treg) cells and dendritic cells, play important roles in the maintenance of peripheral immune tolerance. However, the potential roles of these cells in MLNs in the development of endotoxin tolerance remain largely unknown. Recent research work showed that CD4⁺Foxp3⁺ Treg cells contributed to the development of endotoxin tolerance. Here, we further analyzed the possible change on CD4⁺Foxp3⁺Tregs population in MLNs in murine LPS-induced endotoxin tolerance model. Our data showed that the proportion and absolute number of CD4⁺Foxp3⁺Tregs, expressing altered levels of CTLA4 and GITR, significantly increased in MLNs of murine LPS-induced tolerance model. Moreover, the expression level of TGF-β in MLNs also increased obviously. Furthermore, TGF-β blockade could obviously reduce the proportion and absolute number of CD4⁺Foxp3⁺Tregs in MLNs and subsequently impair the protection effect against LPS rechallenge. Of note, we found that tolerogenic dendritic cell (Tol-DC), expressing lower levels of MHC-II and CD86 molecules, dominantly secreted TGF-β in MLNs in murine LPS-induced tolerance model. In all, our data provided an unknown phenomenon that the total cell number of CD4⁺Foxp3⁺Tregs significantly increased in MLNs in endotoxin tolerance, which was related to MLN-resident TGF-β secreting CD11c⁺DCs, providing a new fundamental basis for the understanding on the potential roles of MLN-resident immune cells in the development of endotoxin tolerance.

内毒素耐受性是预防致死性感染和炎症反应的重要状态，这与先天免疫细胞的参与密切相关。此外，肠系膜淋巴结（MLNs）驻留的免疫细胞，例如CD4 ⁺ Foxp3 ⁺调节性T（Treg）细胞和树突状细胞，在维持外周免疫耐受中起重要作用。但是，这些细胞在MLNs中内毒素耐受性发展中的潜在作用仍然未知。最近的研究工作表明，CD4 ⁺ Foxp3 ⁺ Treg细胞有助于内毒素耐受性的发展。在这里，我们进一步分析了CD4 ⁺ Foxp3 ⁺小鼠LPS诱导的内毒素耐受模型中MLN中的Tregs种群。我们的数据显示，在小鼠LPS诱导的耐受性模型的MLN中，表达改变的CTLA4和GITR水平的CD4 ⁺ Foxp3 ⁺ Treg的比例和绝对数量显着增加。而且，TGF-β在MLNs中的表达水平也明显升高。此外，TGF-β阻断剂可明显降低CD4 ⁺ Foxp3 ⁺的比例和绝对数量MLN中的Treg并随后削弱了针对LPS再挑战的保护作用。值得注意的是，我们发现在小鼠LPS诱导的耐受性模型中，表达较低水平的MHC-II和CD86分子的致耐受性树突状细胞（Tol-DC）在MLNs中主要分泌TGF-β。总之，我们的数据提供了一个未知的现象，即内毒素耐受的MLN中CD4 ⁺ Foxp3 ⁺ Tregs的总细胞数显着增加，这与MLN驻留的TGF-β分泌CD11c ⁺ DC有关，为新的基础奠定了基础。理解MLN驻留免疫细胞在内毒素耐受性发展中的潜在作用。