BioBran, enzymatically modified arabinoxylan from rice bran was tested for its possible effects on in vitro maturation of human dendritic cells (DC). Immature DC (iDC) derived from plastic-adhered, IL-4 and GM-CSF treated peripheral monocytes (Mo) were further cultured with cytokine maturation mix 1 (CMM1; TNF-alpha, IL-1beta and IL-6) or CMM2 (LPS and IFN-gamma) to induce their maturation into mature DC (matDC1 or matDC2, respectively). Different concentrations of BioBran (10, 100, 400 and 1000 microg/ml) were applied in the presence or absence of relevant CMM to assess the effects of BioBran on DC maturation processes. BioBran induced maturation of iDC, as these cells cultured with IL-4/GM-CSF/BioBran down-regulated CD14 and CD1a antigens on cell surface and significantly increased expression of maturation marker CD83. The increase of surface density of costimulatory molecules CD80 and CD86 on iDC in the presence of BioBran was also observed. In addition, BioBran induced functional maturation of iDC, confirmed by decreased endocytic activity of iDC. Further emore, BioBran enhanced maturation potential of cytokine mixes, as both matDC1 and matDC2 exposed to BioBran completely lost CD14 and upregulated CD83, CD80 and CD86 antigens, in comparison to DC matured with the relevant CMM alone. BioBran also increased CD123 antigen expression on all DC subsets. Interestingly, matDC2 matured in the presence of BioBran (400microg/ml) expressed higher levels of CD123 and lower levels of CD11c cell surface antigens, the phenotype represented by CD11c<sup>dim</sup> CD123<sup>bright</sup> plasmacytoid DC population. These data demonstrate that BioBran is a potent enhancer of DC maturation and suggest that BioBran might be a useful agent to create the environment that favours DC maturation.
Keywords: Dendritic cell, maturation, BioBran, buffy coat.