Source Naturals Mushroom Immune Defense is a blend of mushroom mycelia and extracts from 16 of the most well-studied species of health-supportive mushrooms. Although the exact mechanisms of action in the body are not yet fully understood, researchers propose that constituents of these mushrooms may support natural killer (NK) cell, T-cell, and macrophage activity, and cytokine production. By carefully combining these mushrooms and fortifying them with extracts, Source Naturals Mushroom Immune Defense offers a broad-spectrum, high potency, complete mushroom product.