16-Mushroom Complex. Suitable for Vegetarians. 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.