Most studies on maitake have utilized a bioactive extract known as the D-fraction. The D-fraction is typically extracted from the mushroom’s fruiting body and is composed of a proteoglucan, which is a beta-glucan and protein complex in a ratio ranging from 80:20–99:1.[1][2] It appears that maitake’s D-fraction exerts its antitumor effects by inducing apoptosis in, and autophagy of, cancerous cells.[3]
Moreover, preclinical[3] and clinical[4][2] studies have demonstrated that maitake’s D-fraction works by modulating the immune system. Preclinical studies have observed that maitake increases the activation of T cells, specifically CD4+ and CD8+ T cells, and enhances the secretion of immunostimulatory cytokines (i.e., IL-2, IL-12, TNF-α, and IFN-γ)[3] Clinical trials involving individuals with cancer have confirmed these findings, demonstrating increased levels of stimulatory cytokines (e.g, IL-2)[2], enhanced T cell activation, and increased NK cell activity[4]. Additionally, one study noted an increase in levels of interleukin 10 (IL-10), which at least partially explains maitake’s potential immunosuppressive mechanism.[2]