β-D-Glucan Promotes the Activities of Macrophages and Natural Killer Cells: In Vitro Evidence for Immune Enhancing Effect

초록

The innate immune system serves as the body’s first line of defense against harmful germs and substances. Key components of this system include macrophages, monocytes, dendritic cells, neutrophils, and natural killer (NK) cells. Insoluble polysaccharides produced by bacteria, yeast, fungi, and algae are known to boost immune function. Specifically, an insoluble yeast (1→3)-(1→6)-β-D-glucan has been reported to benefit the immune system by reducing the severity of upper respiratory infections through inflammation modulation. We hypothesized that the beneficial effects of β-D-glucan are due to its enhancement of the innate immune functions. To test this hypothesis, we examined whether β-D-glucan stimulates mouse macrophages (RAW 264.7 cells) and rat splenic NK cells. The β-D-glucan from Saccharomyces cerevisiae, provided by Leiber GmbH (Bramsche, Germany), was used in our study, and the following results were obtained: When treated with β-D-glucan (0, 30, 100, 300, 1,000 μg/mL), RAW 264.7 cells showed significant increases in cell viability and phagocytosis of neutral red. Additionally, there were significant increases in nitric oxide (NO) production and the expressions of cyclooxygenase-2 and NO synthase 2 compared to the control group (0 μg/mL). Furthermore, when co-cultured with YAC-1 cells (NK-sensitive fibroblasts) in the presence of β-D-glucan (0, 30, 100, 300, 1,000 μg/mL), cytolysis of YAC-1 cells was significantly increased compared to the control group (0 μg/mL). These results indicate that β-D-glucan stimulates the cells involved in innate immunity, thereby enhancing the body’s defense mechanisms against various pathogens.

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