Regulation On Phenotypic And Functional Maturation Of Dendritic Cells By Astragalus Mongholicus Polysaccharides

[Background and Objective] Dendritic cells (DC) are professional antigen-presenting cells which play an important role in initiating T-cell responses against microbial pathogens and tumors. Immature DC capture and process exogenous antigens in peripheral tissues and then they begin to migrate to lymphoid organs, at the same time they express the major histocompatibility complex (MHC) class â…¡ antigen on their cell surface gradually which is necessary for antigen presentation to helper T cells, when the maturing DC finally arrive at lymphoid organs, they become matured DC and have the ability of presenting antigens to T cells with the help of MHC class â…¡ molecules. In one word, immature DC are characterized by a high capacity for antigen uptake and process and by low levels expression of surface MHC class â…¡ molecules. The mature DC is characterized by the decreased ability of antigen uptake and process, by high levels expression of surface MHC class â…¡ molecules, and by producing IL-12 when stimulated. Consequently mature DC gain a high capacity to prime T cells. It is generally believed that down-regulation of antigen uptake and up-regulation of MHC class â…¡ molecules are combined in vivo.The traditional Chinese herb can be categorized by different functions and Astragalus mongholicus belongs to the kind which can reinforce the functions oforganisms, Astragalus mongholicus polysaccharides (ASP) which are isolated from the root of Astragalus mongholicus have been reported to be effective in modulating immune functions and inhibiting tumour growth. The immunomodulatory effects of ASP were extensive, including promoting humoral immunity and cellular immunity, improving the immune functions of the immunosuppressive model mice, and modulating the production of cytokines. However, little is known about ASP immunomodulating effects on murine bone marrow-derived DC. Thus phenotypic and functional maturation of DC was investigated by ASP isolated from Astragalus mongholicus in this study.In this study, we performed basic research to explore the effects of ASP on the phenotypic and functional maturation of DC derived from murine bone-marrow cells. [Methods] 1.Murine bone marrow-derived dendritic cells culture: bone marrow cells were cultured in RPMI-1640 containing GM-CSF and 1L-4, replace the medium on day 3 and purify DC on day 5. 2. Immunofluorescence staining and flow cytometry to determine DC surface molecules CDllc fP MHC II molecules: cells were stained with R-PE-I-A/I-E and FITC-CDllc, washed and then analyse fluorescence intensity. 3.Immunofluorescence staining and flow cytometry to determine endocytic capacity of DC: DC were harvested and incubated with 1 mg/ml FITC-dextran at 37 *C and 4 "C for 1 h and analyse fluorescence intensity respectively. 4. The level of mouse IL-12 in culture supernatants was determined by a sandwich enzyme-linked immunosorbent assay. 5. DC were processed for a scanning electromicroscope in order to observe their surface ultrastructure. [Results] ASP (10, 50, 100 and 250 u g/ml) could increase the co-expression of CDllc and MHC class II molecules on DC surface, and the 100 u g/ml is the optimal dose. The ability of unstimulated DC to uptake FITC-dextran was higher than that of ASP- or LPS-treated DC. We analyzed the concentration of IL-12 secreted by DC using ELISA. ASP-treated DC secreted higher level of IL-12 thanuntreated DC. And ASP- or LPS-treated DC displayed a more mature morphology,with long protrusions, while untreated-DC displayed shorter protrusions thanstimulated DC.[Conclusion] l.ASP can increase the co-expression of CDllc and MHC class IImolecules on DC surface. 2. ASP can inhibit the endocytic capacity of DC. 3. ASP canincrease secretion of IL-12 of DC. 4.ASP can promote the maturation of DC inmorphology.In one word, ASP can induce the phenotypic and functional maturation of DC.