The dynamic expression of cytokines and phenotypes during the differentiation process of dendritic cell precursors (pre-DCs) to mature dendritic cells (DCs) was investigated,and the effects of inflammatory stimulation with lipopolysaccharide (LPS) on DCs differentiation were understood.The differentiation of bone marrow cells isolated from Balb/c mice was induced to DCs in an 8-day cell culture system with RPMI-1640 complete culture medium containing 10％ FBS,20 ng/mL recombinant mouse granulocyte-macrophage colony-stimulating factor (rmGM-CSF) and 10 ng/mL recombinant mouse interleukin-4 (rmIL-4).On the day 3,6 and 7 after culture,DCs were divided into non-LPS group and LPS group,given 500 ng/mL LPS for 24 h stimulation and no stimulation respectively.The expression levels of CD 1 l c+,MHC-Ⅱ +,CD40+,CD80+ and CD86+ were detected by flow cytometry,and those of IL-2,IL-4,IL-10,IL-12 p70 and IFN-γ in the supatant by ELISA.On the day 3 and 6 after culture,the expression of IL-2,IL-4,IL-10 and IFN-γ in DCs showed no significant differences between non-LPS group and LPS group,whereas the differences were significant at day 7.The expression levels of cytokines (for IL-2,IL-4,IL-10,IFN-γ and IL-12 p70:152.86±6.91,778.33±8.35,44.55±2.54,5.8.26±1.09 and 2423.00±57.21 pg/mL respectively) in LPS group were higher than those in non-LPS group,especially IL-12 p70 increased obviously at day 7.It was concluded that during the differentiation process of pre-DCs to mature DCs,LPS stimulates DCs producing large amounts of IL-12 p70 and Thl-type cytokines as compared with Th2-type cytokines,and day 7 may be a key time-point for DCs polarization.