An immunomodulatory protein, Ling Zhi-8, induced activation and maturation of human monocyte-derived dendritic cells by the NF-κB and MAPK pathways

Mushroom product induces a Th1 response and may possess a potential effect in regulating immune responses. Ganoderma lucidum, an oriental medicinal mushroom, has been widely used in Asia to promote health and longevity. LZ‐8 is a protein derived from the fungus G. lucidum and has immunomodulatory capacities. In this study, we investigated the immune modulatory effects of rLZ‐8 on human monocyte‐derived DCs. Treatment of DC with rLZ‐8 resulted in the enhanced cell‐surface expression of CD80, CD86, CD83, and HLA‐DR, as well as the enhanced production of IL‐12 p40, IL‐10, and IL‐23, and the capacity for endocytosis was suppressed in DCs. In addition, treatment of DCs with rLZ‐8 resulted in an enhanced, naïve T cell‐stimulatory capacity and increased, naïve T cell secretion of IFN‐γ and IL‐10. Neutralization with antibodies against TLR4 inhibited the rLZ‐8‐induced production of IL‐12 p40 and IL‐10 in DCs. rLZ‐8 can stimulate TLR4 or TLR4/MD2‐transfected HEK293 cells to produce IL‐8. These results suggested an important role for TLR4 in signaling DCs upon incubation with rLZ‐8. Further study showed that rLZ‐8 was able to augment IKK, NF‐κB activity, and also IκBα and MAPK phosphorylation. Further, inhibition of NF‐κB by helenalin prevented the effects of rLZ‐8 in the expression of CD80, CD86, CD83, and HLA‐DR and production of IL‐12 p40 and IL‐10 in various degrees. To confirm the in vitro data, we investigated the effect of rLZ‐8 further on antigen‐specific antibody and cytokine production in BALB/c mice. Immunization with OVA/rLZ‐8 showed that the anti‐OVA IgG2a, IFN‐γ, and IL‐2 were increased significantly compared with OVA alone in BALB/c mice. In conclusion, our experiments demonstrated that rLZ‐8 can effectively promote the activation and maturation of immature DCs, preferring a Th1 response, suggesting that rLZ‐8 may possess a potential effect in regulating immune responses.