Effects of the Linear Fragments of Beta-(1→3)-Glucans on Cytokine Production in vitro

Beta-glucans, homopolysaccharides composed of 3,6-branching β-(1→3)-D-glucan chains, attract great interest as inducers of cytokine synthesis. In this work, we studied the ability of linear fragments of beta-glucan chains to activate cytokine synthesis. Synthetic nona-β-(1→3)-D-glucoside (SO) representing a linear fragment of beta-glucan chain, endotoxin (ED), and natural β-(1→3)-D-glucan (GL) were tested for their role as inducers of cytokines in whole peripheral blood cultures collected from 17 individuals. The concentrations of IL-12p70, IFN-γ, IL-2, IL-10, IL-8, IL-6, IL-4, IL-5, IL-1β, TNF-α, and TNF-β were measured in the supernatants after 2, 24, and 48 h of cell culturing. SO, ED, and GL stimulated production of pro-inflammatory IFN-γ, IL-1β, IL-2, IL-6, IL-8, TNF-α and anti-inflammatory IL-10. The highest levels of biosynthesis after stimulation with SO were registered for IL-6, IL-8, and TNF-α. SO stimulated production of all cytokines (except IFN-γ) to a lesser extent than ED and GL. The IFN-γ/IL-10 (Th1/Th2) ratios after 24 and 48 h of culturing were 3.1 and 7.5 for SO; 0.03 and 0.1 for GL; and 0.06 and 0.2 for ED, respectively. The results indicate that linear fragments of beta-glucans cause a more pronounced shift of immune response towards the pro-inflammatory (Th1) type than beta-glucan itself.