Modulation of immunol-properties by chito-oligosaccharide

Objective:To study the immunol-regulation properties of chito-oligosaccharides(COS) with 3-7 degree of polymerization,which are prepared by enzymatic hydrolysis.Methods:Chitosanase founded by our research group was used to prepare chito-oligosaccharides through the enzyme hydrolysis method,and HPLC method was used to identify the composition of COS.COS was then labeled with fluorescein isothiocyanate(FITC) to get FITC-COS.Phagocytosis of COS by mouse peritoneal macrophages' and its relationship with TOLL-like receptor 4(TLR4) was investigated.The effects of different concentrations of COS on the proliferation,neutral red phagocytosis ability,and tumor necrosis factor(TNF-alpha) secretion of mouse peritoneal macrophages were then tested.Mice were administrated with different doses of COS to elucidate the impact of COS on serum IgG and IgM levels and on the thymus,spleen index of mouse.Results:HPLC analysis results showed that COS,prepared by chitosanase hydrolysis,mainly consist of 3-7 degree of polymerization of monosaccharide.Fluorescence microscopy results showed that FITC-COS could be phagocytized by mouse peritoneal macrophages in a time-dependent manner.Pretreatment of macrophages with TLR4 monoclonal antibody for 1hr,phagocytosis of COS was almost completely inhibited.The phagocytosis and TNF-α secretion abilities of macrophage were all significantly enhanced after COS was phagocytized.The results of in vivo studies showed that administration of mice with COS could significantly increase the spleen index and serum IgG levels.While the thymus index and serum IgM levels were not significantly changed.Conclusion:COS with 3-7 polymerization degree can be phagocytized by macrophage and then activate macrophages.COS has good in vitro and in vivo immunological function.The activation of macrophages by COS is mediated by the TLR4 receptor on cell surface.