Type I IFN regulate DC turnover in vivo.

DC are the most potent antigen-presenting cells that recognise signs of infection and serve as the main activators of naïve T cells. We have previously shown that type I IFN (IFN-I) are produced by DC and can act in an autocrine manner to activate DC. In the present study, we have investigated the role of IFN-I in regulating the turnover and lifespan of DC. We found that DC, especially the CD8alpha(+) subset, from type I IFN receptor knock out (IFNAR KO) mice, display a reduced turnover rate when compared with DC from WT mice, as revealed by BrdU labelling kinetics. In vitro, IFNAR KO BM precursor cells cultured in the presence of GM-CSF generated CD11c(+) DC less efficiently than WT BM, and the IFNAR KO DC that arose displayed reduced migratory ability. Interestingly, splenic DC from IFNAR KO mice exhibited a higher survival rate in short-term culture compared with control DC. Exposure to IFN-I in vivo markedly increased the turnover rate of splenic DC, particularly CD8alpha(+) DC, which was preceded by a transient induction of apoptosis. In accordance with this, IFN-I stimulated the apoptosis of splenic DC in vitro. Overall, our data indicate that IFN-I are important regulators of DC turnover in vivo and suggest that these cytokines may exert this function through the modulation of multiple processes involving DC apoptosis, proliferation and migration.