Preferential induction of Th17 cells in vitro and in vivo by Fucogalactan from Ganoderma lucidum (Reishi)

The mushroom known as Reishi (Ganoderma lucidum) has been used as an herbal medicine for tumor treatment and immune system activation. Because its effects on the differentiation of effector T helper cells have not yet been fully understood, we investigated the effects of Reishi and those of its principal ingredient, β-glucan, on the activation of dendritic cells and the differentiation of Th17 cells. Reishi extracts as well as purified β-glucan (Curdran) activated DCs and caused them to produce large amounts of IL-23. β-glucan also enhanced and sustained the transcription of IL-23p19. The MEK-ERK signaling pathway positively regulates IL-23p19 transcription in β-glucan-stimulated DCs. In a mixed leukocyte reaction, Reishi-stimulated DCs preferentially induced Th17 cells. Furthermore, orally-administrated Reishi increased the percentages of Th17 cells and the transcription levels of antimicrobial peptides. Our results show that Reishi and β-glucan activate DCs to produce large amounts of IL-23, which induces Th17 differentiation both in vitro and in vivo.

► Reishi and β-glucan (Curdran) induce large amounts of IL-23 but not IL-12 from dendritic cells. ► β-Glucan enhanced and sustained the transcription of IL-23p19 through the MEK-ERK pathway. ► Reishi-stimulated DCs preferentially induced Th17 cells. ► Oral administration of Reishi increased the percentages of Th17 cells in vivo.