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Aim: The aim of this study was to investigate endocytosis, MHC-Ⅱ expression and co-stimulatory molecule expression, as well as interleukin-12 (IL-12) production, in bone marrow dendritic cells (DCs) derived from endotoxin tolerant mice.Methods: Endotoxin tolerance was induced in C57BL/10J mice through four consecutive daily intraperitoneal injections of 1.0 mg/kg of 055:B5 Escherichia coli lipopolysaccharide (LPS). Bone marrow DCs were isolated in the presence of GM-CSF and IL-4 and purified by anti-CD11c Micro beads. FITC-dextran uptake by DCs was tested by flow cytometric analysis and the percentage of dextran-containing cells was calculated using a fluorescence microscope. The expression of surface MHC-Ⅱ, CD40, CD80, and CD86 was also detected by flow cytometric analysis. An ELISA was used for the measurement of IL-12 production by DCs with or without LPS stimulation.Results: Endotoxin tolerance was successfully induced in C57BL/10J mice, evidenced by an attenuated elevation of systemic TNF-α. DCs from endotoxin tolerant mice possessed enhanced dextran endocytosis ability. The expression of surface MHC-Ⅱ and CD80 was higher in DCs from endotoxin tolerant mice than in DCs from control mice, whereas the expression of CD40 and CD86 was not altered. Compared with DCs from normal control mice, DCs from endotoxin tolerant mice produced less IL-12 after subsequent in vitro stimulation with LPS.Conclusion: These data suggest enhanced endocytosis, selective up-regulation of MHC-Ⅱ and CD80 and IL-12 suppression in DCs during in vivo induction of endotoxin tolerance.