Mulberry leaf polysaccharide enhances cyclophosphamide-induced immune response in mice via MAPK/NF-κB pathway and gut microbiota regulation

• MLP can enhance the immune response in immunosuppressed mice. • MLP regulates the immune response in mice by activating the MAPK and NF-kB pathways. • MLP can enhance the immune function of mice by increasing Lactobacillus . This study provides insight into the effects of a Mulberry leaf polysaccharide (MLP) on a model of cyclophosphamide (CTX)-induced immunosuppression, revealing the complex ways in which MLP affects the immune system and the balance of the intestinal microbiota. MLP effectively counteracts the deleterious effects of CTX on the intestines and immune organs such as the spleen. It stimulated an increase in the number of CD4 + and CD8 + T-lymphocytes, as well as the proliferation of splenic lymphocytes, macrophages, phagocytic activity, and natural killer (NK) cell function, thereby enhancing the immune response in CTX-affected mice. In addition, MLP initiated the activation of MAPK and NF-κB signaling pathways downstream of Toll-like receptor 4 (TLR4). This activation promotes the production of key cytokines such as interleukin II (IL-2) and tumor necrosis factor-alpha (TNF-α), thereby reducing the CTX-induced immunosuppressive effects. Meanwhile, the effects of MLP extended to the gut microbiota, where it was observed to enhance the diversity and abundance of microbial species, especially promoting the growth of beneficial bacteria such as Lactobacillus . These findings suggest that MLP holds promise as an immunomodulatory supplement or functional food ingredient specifically designed to attenuate CTX-induced immunosuppressive effects.