Effects of Beta-Glucans on Different Immune Cell Populations and Cancers

Abstract

β-Glucan is one of the most abundant and widespread form of naturally occurring polysaccharides found inside the cell wall of bacteria, plants and fungi including the medicinal mushrooms. All forms of β-glucans have a basic structure of glucose polymers linked together by a 1 → 3 linear β-glycosidic chain core. They then differ from each other by their length of the core and the type and extent of branching structures of the two main forms of 1 → 4 or 1 → 6 glycosidic chains branching (Stone and Clarke, 1992). These branching assignments tend to be species specific, for instance, 1 → 6 side branches for fungal β-glucans in contrast to 1 → 4 side branches for bacterial β-glucans. There are insoluble or particulate forms versus the aqueous soluble forms of β-glucans which act on different target receptors. Various conformations such as triple helix, single helix or random coils also exist. The correlation between β-glucans structure and their biological potency has been elaborated in one of the recent reviews (Barsanti et al., 2011); our review will mainly focus at how β-glucans affect the diverse immunological cells and cytokines, especially those related to anti-cancer action. There are mounting evidences suggesting β-glucans as potent immunomodulators on both innate and adaptive immunity. After our previous review of the immunomodulatory and anti-cancer effects of β-glucans (Chan et al., 2009), there emerged a rich resource of studies on multi-directional immunomodulatory effects of β-glucans. The findings are complex and sometimes conflicting especially to the immune cell subsets. This review therefore aims to provide an up-to-date information on the effects of β-glucan to different immune cell populations and then postulate some possible translational strategies to utilize such knowledge in both anti-cancer research and clinical immunotherapeutic application. © 2012 Elsevier Ltd.