Abstract: In recent years, the immunomodulatory activity of fungal polysaccharides has become a hot spot in the field of health foods. In the present study, Cordyceps militaris polysaccharides (CMP) were used to investigate the mechanism for its immunoregulatory effect on macrophage RAW264.7 cells. Thiazolyl blue assay results showed that CMP had no cytotoxicity and at doses of 100 and 200 μg/mL could significantly promote the proliferation of RAW264.7 cells. The neutral red staining, Griess and ELISA results showed that CMP at a concentration of 25–200 μg/mL increased the phagocytic activity and the secretion of nitric oxide (NO) and interleukin-1β (IL-1β) in RAW264.7 cells in a dose-dependent manner; tumor necrosis factor-α (TNF-α) secretion increased first and then decreased after reaching the highest value at 100 μg/mL. Inhibitor neutralization assay showed that CMP was significantly less able to induce immune response in RAW264.7 cells when Toll-like receptors 4 (TLR4) and mannose receptor (MR) were inhibited, indicating that both TLR4 and MR were CMP-activated macrophage receptors. Western blot results showed MAPK signaling was also involved in CMP-induced secretion of NO, TNF-α and IL-1β in RAW264.7 cells. Therefore, TLR4 and MR/MAPK signal transduction pathways play an important role in CMP-induced immune response in macrophage RAW264.7 cells.

Key words: Cordyceps militaris polysaccharides, RAW264.7 cell, Toll-like receptor 4, mannose receptor, mitogen-activated protein kinase