Longan polysaccharides promote Th1 and Treg cell differentiation via dendritic cells

In this study, the activating effects of a glucan derived from longan (LP) on primary bone marrow dendritic cells (BMDCs) and their role in mediating T cells differentiation were investigated. LP significantly reduce phagocytosis in dendritic cells (DCs) while augmenting CD80, CD86, and MHC II surface molecule expression, and promoting the IL-6, IL-10, and IL-12 secretion. RNA-seq, immunofluorescence, and Western blot analysis indicated that LP primarily activate DC through the Toll-NF-κB pathway, upregulating genes related to maturation and antigen presentation, thereby regulating cytokine release and T cell activation. In addition, LP promote the CD3+ T cells proliferation and increase the CD3+ CD4+ and CD3+ CD8+ T cells ratio through DC mediation. Notably, LP increase the proportion of CD3+ CD4+ IFN-γ+ Th1 cells and CD3+ CD4+ CD25+ Foxp3+ T regulatory cells, while concurrently decreasing CD3+ CD4+ IL-4+ Th2 cells. These results indicate that LP promotes T cell differentiation towards Th1 and Treg subsets through dendritic cell mediation, enhancing a Th1-dominated cellular immune response alongside Treg-mediated immune regulation.