Modified Arabinoxylan Rice Bran (Mgn-3/Biobran) Enhances Intracellular Killing of Microbes by Human Phagocytic Cells in Vitro

Phagocytic cells, comprised of neutrophils and moncytyes/macrophages, play a key role in the innate immune response to infection. Our earlier study demonstrated that arabinoxylan rice bran (MGN-3/Biobran) activates murine peritoneal macrophage and macrophage cell lines. In this study, we investigated whether MGN-3 can upregulate the phagocytic activity of human phagocytes in peripheral blood to phagocytize Escherichia coli (E. coli), trigger the oxidative burst and produce cytokines. Phagocytic cells were pre-labeled with dichlorofluorescin diacetate dye and were incubated with phycoerythrin-labeled E. coli in the presence or absence of MGN-3. Phagocytosis and oxidative burst were assessed by flow cytometry. Results showed that treatment with MGN-3 enhanced the phagocytosis of E. coli by neutrophils and moncytes. This was associated with an increased oxidative burst. In addition, it caused a significant induction of cytokines (TNF-α, IL-6, IL-8 and IL-10); the effect was detected at 1 μg/ml and increased in a dose-dependent manner (P≤ 0.01). Notably, MGN-3 alone had no effect on the growth of 31 strains of bacteria suggesting that MGN-3 modulates phagocytic cellular function. These findings may have applications in the treatment of infections in the elderly and in immunocompromised patients.