Tolerogenic dendritic cells induced the enrichment of CD4+Foxp3+ regulatory T cells via TGF-β in mesenteric lymph nodes of murine LPS-induced tolerance model.

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.