Beta-Glucans and Polysaccharides
Fungi are remarkable for the variety of high-molecular-weight polysaccharide structures that they produce.
Polysaccharides represent structurally diverse biological macromolecules with wide-ranging physiochemical properties.
β-Glucans (beta-glucans) are naturally occurring polysaccharides.
They comprise a group of β-D-glucose polymers, sugars naturally occurring in the cell walls of bacteria, fungi, yeasts, algae, lichens, and plants, such as oats and barley.
There are variants like β-(1,3)-glucans, β-(1,6)- and β-(1,4)-structures.
These polysaccharides contain long chains of branching sugars that interact in different ways with various receptors on cell surfaces, triggering other biochemical responses.
Beta-glucans have significantly differing physicochemical properties dependent on source, and are potent stimulants of innate immunity.
These substances increase host immune defense by activating the complement system, enhancing macrophages and natural killer cell function.
Beta-glucans are known as “biological response modifiers” because of their ability to activate the immune system.
Immunologists have discovered that receptors on the surface of innate immune cells called dectin-1 and complement receptor 3 (CR3 or CD11b/CD18) are responsible for binding to beta-glucans, allowing the immune cells to recognize them.
Innate immunity reactions are induced by all three variants: β-(1,3)-glucans, β-(1,6)- and β-(1,4)-structures.
The majority of research on biological activities of glucans has focused on β-(1,3)-Glucans, which have been implicated in relation to fungal exposure-associated respiratory symptoms, and as important stimulatory agents in anti-fungal immune responses.
The induction of cellular responses by mushroom and other beta-glucans is likely to involve their specific interaction with several cell surface receptors, as complement receptor 3 (CR3; CD11b/CD18), lactosylceramide, selected scavenger receptors, and dectin-1 (betaGR). Beta-Glucans also show anticarcinogenic activity.
They can prevent oncogenesis due to the protective effect against potent genotoxic carcinogens.
As an immunostimulating agent, which acts through the activation of macrophages and NK cell cytotoxicity, beta-glucan can inhibit tumor growth in the promotion stage too.
Anti-angiogenesis can be one of the pathways through which beta-glucans can reduce tumor proliferation, prevent tumor metastasis.
Beta-glucan is an adjuvant to cancer chemotherapy and radiotherapy demonstrated a positive role in the restoration of hematopiesis following by bone marrow injury.
Immunotherapy using monoclonal antibodies is a novel strategy for cancer treatment.
These antibodies activate the complement system and opsonize tumor cells with iC3b fragment. In contrast to microorganisms, tumor cells, as well as other host cells, lack Beta-Glucan as a surface component and cannot trigger complement receptor 3-dependent cellular cytotoxicity and initiate tumor-killing activity.
Beta-glucans can boost the immune system in people whose body defenses have been weakened by conditions such as
- chronic fatigue syndrome,
- physical and emotional stress, or by
- treatments such as radiation or chemotherapy.
Beta-glucans are also taken for
- influenza (flu),
- swine flu,
- respiratory tract infections,
- Lyme disease,
- ear infections,
- ulcerative colitis and Crohn’s disease,
- irritable bowel syndrome,
- pain after surgery,
- rheumatoid arthritis, and
- multiple sclerosis.
- Vannucci, L; Krizan, J; Sima, P; Stakheev, D; Caja, F; Rajsiglova, L; Horak, V; Saieh, M (2013). “Immunostimulatory properties and antitumor activities of glucans (Review)”. International Journal of Oncology. 43 (2): 357–64.
- Noss I, Doekes G, Thorne PS, Heederik DJ, Wouters IM. Comparison of the potency of a variety of β-glucans to induce cytokine production in human whole blood. Innate Immun. 2013;19(1):10–19.
- Akramiene D, et.al. Effects of beta-glucans on the immune system. Medicina (Kaunas). 2007;43(8):597-606.