The human immune system has a remarkable ability to distinguish between the body’s own cells, recognized as “self” and foreign cells, as “nonself”, to mediate the immune responses. Mushroom β-glucans are a large group of macromolecules that are not naturally synthesized inside the human body, so these compounds are recognized as non-self-molecules, which activate the immunity. Mushroom polysaccharides or β-glucans are thought to provide their anti-tumor action primarily through the activation of the immune response of the host organism. In most cases mushroom polysaccharides do not directly affect tumor cells.
Certain β-glucans from medicinal mushrooms appear to activate cell-mediated and humoral immunity via activation of different immune cells, leading to elimination of tumor cells or pathogens. The activated macrophages (containing β-glucans) preferentially attack dead cells and intracellular pathogens. These macrophages also produce cytokines that prime natural killer cells and T lymphocytes, both of which are cytotoxic to tumor cells, via different mechanisms. Natural killer cells secrete chemical substances that destroy tumor cells by bursting cell membranes. Neutrophils effectively destroy targeted cells by cell mediated phagocytosis. In this review were described the hypothesized mechanism of action for fungal β-glucans against cancer cells.