Regulation of the lifespan in dendritic cell subsets.

The lifespan of dendritic cells (DCs) can potentially influence immune responses by affecting the duration of DCs in stimulating lymphocytes. Significant differences in the lifespan have been reported for various DC subsets, however, the molecular mechanisms for regulating such differences between DC subsets remain unclear. In this study, we compared the apoptosis signaling molecules in two major DC subjects, the myeloid DCs (mDCs) and plasmacytoid DCs (pDCs). We observed a lower ratio between anti-apoptotic Bcl-2/Bcl-xL and pro-apoptotic Bax/Bak in shorter-lived myeloid DCs (mDCs) than in longer-lived plasmacytoid DCs (pDCs) or T cells. Transfection with Bcl-2 or Bcl-xL prolonged the survival of mouse primary mDCs in vitro, while deletion of Bcl-2 accelerated DC turnover in vivo. In addition, the ratios between anti-apoptotic Bcl-2/Bcl-xL and pro-apoptotic Bax/Bak could be regulated in DCs. Signaling from toll-like receptors (TLRs) up-regulated Bcl-xL and improved DC survival. Our data suggest that differential expression of apoptosis signaling molecules regulates the lifespan of different DC subsets.