From the Manufacturer:
Maitake, like most mushrooms, contains complex polysaccharides (including beta-d-glucan) that promote immunity.
Maitake has also been shown in studies to possess other amazing properties. For example, the July 1997 Biological and Pharmaceutical Bulletin published results from animal studies that suggest maitake may promote a healthier cholesterol level.
Another study just published in the May 2005 journal Nutrition found that maitake helped enhance anti-tumor effects in mice by activating immunocompetent cells (such as T-cells). The researchers concluded that maitake may ultimately provide a potential benefit for human cellular health.