Time-dependent effect of E. coli LPS in spleen DC activation in vivo: Alteration of numbers, expression of co-stimulatory molecules, production of pro-inflammatory cytokines, and presentation of antigens.

Lipopolysaccharide (LPS) is a well-known stimuli of dendritic cells (DCs). However, in vivo spleen DC maturation by Escherichia coli (E.coli) LPS has not been fully investigated. In this study, we examined the effect of LPS on the activation of spleen DCs and its subsets in a time-dependent manner on mice in vivo. The frequency, number and migration of spleen conventional DCs (cDCs) were increased 6 and 12h after completion of LPS treatment. Those increased DC numbers in spleen were then gradually decreased with apoptosis of the DCs. The highest levels of co-stimulatory molecule expression in the spleen cDCs and their subsets occurred 18h after LPS treatment, while the pro-inflammatory cytokines reached their maximum in the intracellular levels of the spleen cDCs and their subsets 3h after LPS treatment. The antigen presentation of the spleen cDCs and their subsets increased gradually from 3 to 12h after LPS treatment, but those levels decreased rapidly after 18h post-LPS treatment. Thus, by highlighting the importance of time in the stimulation of spleen DCs by LPS in mice in vivo, our data provided a model that could be used by immunologists when considering the manipulation of DC functions in vivo for experimental and clinical applications.