From the Manufacturer:
Made with Organic Mushrooms. Maitake is known as the Dancing Mushroom. Maitake is considered by many scientists to be the most powerful immuno-supporter in the mushroom kingdom and in promoting normal cell growth, particularly in the breasts, lungs and liver. Many fractions of Maitake have been praised for the immunostimulating effect, but as with most natural compounds, the whole is greater than the sum of its parts. Using organic Maitake mycelium and fruitbodies, this product, containing all fractions, has been clinically shown to increase Natural Killer (NK) Cell activity by up to 300%.