Activation of human monocyte-derived dendritic cells in vitro by the biological response modifier arabinoxylan rice bran (MGN-3/Biobran).

Arabinoxylan rice bran (MGN-3/Biobran) is a potent biological response modifier (BRM) that activates natural killer (NK) cells, T cells and monocytes. Currently, little is known regarding the effects of MGN-3 on dendritic cells (DCs), the cell type that bridges innate and adaptive immunity. Therefore, we examined the stimulatory effects of MGN-3 on DCs. Human monocyte-derived DCs were treated with MGN-3 at different concentrations (5-20 microg/ml) for 24 hours in vitro. Activation of DCs was determined by assessing the expression of co-stimulatory and maturation markers (CD40, CD80, CD83, CD86 and HLA-DR) by flow cytometry, and production of cytokines by ELISA. DC function was determined by assessing their ability to activate naïve T cells. Activation of T cells was assessed by measuring cell proliferation and cytokine production. MGN-3 treatment, in a dose-dependent manner, resulted in: 1) up-regulation of the surface expression of CD83 and CD86, on DCs; 2) an increase in the production of pro-inflammatory and immuno-regulatory cytokines (IL-1beta, IL-6, IL-10, TNF-alpha, IL-12p40 and low levels of IL-12p70 and IL-2) by DCs; and 3) MGN-3 stimulated DC induced CD4+T cell proliferation and their production of cytokines, IFN-gamma, IL-10, IL-17. Results suggest that MGN-3 functions as a natural adjuvant for DC activation and thus may be used in DC-based vaccine strategies against infections and cancer.