AHCC (Active Hexose Correlated Compound) is an extract obtained from several species of mushroom mycelia. It helps immunity by increasing the number, activity, and/or production of cytokines, NK cells, macrophages, dendritic cells and T cells. AHCC has also been shown to be effective for many types of cancers. If your blood work reveals that you have low white blood cell count, an important aspect of your immunity, this has been shown to get those back to normal levels.