Objective:To observe the differences of characteristics in activation and proliferation of cord blood lymphocytes stimulated by placenta-derived dendritic-like cells in different stages and further study the role of placental immune cells in pregnancy tolerance and labor onset. Methods:Mononuclear cells were separated mechanically from the mid-term placenta and late placenta. CD14+ cells were obtained by MACS and induced to differentiate into dendritic-like cells through the transebdothelial trafficking system. Flow cytometry was performed to analyze dendritic-like cell phenotype and ELISA assay was performed to detect the levels of IL-12,IL-10 in culture supernatant. CCK-8 assay was used to detect the ability of stimulating the proliferation of cord blood lymphocytes and flow cytometry was used to detect intracellular cytokine produced by stimulated cord blood T lymphocytes. Results:CD14+ monocyte-macrophage obtained from decidual tissue were inoculated into the endothelial monolayer,after two-way-induced culture,cells derived from full-term placenta had an appearance of dendritic morphology changes and highly expressed cell surface markers related to immune activation of dendritic cells,such as CD80,CD86;simultaneously,higher level of IL-12 and very low level of IL-10 were detected in the culture supernatant,and cells had stronge ability of stimulating the cord blood lymphocytes proliferation. They could stimulate cord blood lymphocytes to differentiate into the cells that most of them producing IFN-γ and less of them producing IL-10. However,the induced cells derived from mid-term placenta,expressed low-level CD80 and CD86(P < 0.05),in the culture supernatant,higher level of IL-10(P < 0.05) and very low level of IL-12 (P < 0.05) were detected. Cells had weaker ability in stimulating cord blood lymphocytes(P < 0.05),and stimulated cord blood lymphocytes to differentiate to form more cells producing IL-10(P < 0.05) and less cells producing IFN-γ(P < 0.05). Conclusion:Dendritic-like cells differentiated from placenta-derived monocyte-macrophages in different periods of pregnancy have different immunological characteristics,dendritic-like cells highly expressed CD80-CD86 and high-level IL-12 play a certain role in the termination of immune tolerance in pregnancy and labor onset,dendritic-like cells expressed low-level CD80-CD86,and high-level IL-10 may be involved in immune tolerance during pregnancy.