AHCC is an extract from cultured hyphae of the shiitake mushroom. AHCC balances the immune system without over-stimulating it. S...AHCC is an extract from cultured hyphae of the shiitake mushroom. AHCC balances the immune system without over-stimulating it. Scientific research has shown that AHCC strengthens both the innate and acquired parts of the immune system, as well as having antioxidant effects.