Activation of macrophage mediated host defense against Salmonella typhimurium by Morus alba L.

Background: The innate immune system plays a crucial role in the initiation and subsequent direction ofadaptive immune responses, as well as in the removal of pathogens that have been targeted by an adaptiveimmune response. Objective: Morus alba L. was reported to have immunostimulatory properties that might protect against infectious diseases. However, this possibility has not yet been explored. The present study investigated the protective and immune-enhancing ability of M. alba L. against infectious disease and the mechanisms involved. Design: To investigate the immune-enhancing effects of M. alba L., we used a bacterial infection model. Results and discussions: The lifespan of mice infected with a lethal dose of Salmonella typhimurium (1 × 107colony forming units – CFU) was significantly extended when they were administered M. alba L. Furthermore,M. alba L. activated macrophages, monocytes, and neutrophils and induced Th1 cytokines (IL-12,IFN-γ, TNF-α) in mice infected with a sublethal dose (1 × 105 CFU) of S. typhimurium. M. alba L. significantlystimulated the uptake of bacteria into peritoneal macrophages as indicated by increased phagocytosis.Peritoneal macrophages derived from C3H/HeJ mice significantly inhibited M. alba L. induced NO productionand TNF-α secretion compared with peritoneal macrophages derived from C3H/HeN mice. Conclusions: These results suggest that the innate immune activity of M. alba L. against bacterial infection inmice occurs through activation of the TLR4 signaling pathway.