Plasmacytoid dendritic cells regulate host immune response to Citrobacter rodentium induced colitis in colon‐draining lymph nodes

AbstractDendritic cells (DCs) are first in line to sense invading microbes and to deliver signals to other immune cells. Plasmacytoid DCs (pDC) produce high amounts of type I interferons (IFNs) but also regulate immune responses. Using the Clec4C (BDCA2)‐diphtheria toxin receptor mouse model allowing conditional pDC depletion, we identified an essential role for pDCs in regulating intestinal inflammation locally in the gut. In pDC‐depleted mice, Citrobacter rodentium infection led to enhanced activation of conventional DCs and induction of IFN‐γ‐producing Th1‐cells in colon‐draining lymph nodes, while induction of Foxp3+/CD25+ Treg and IL‐17‐producing Th17 cells was impaired. Concomitantly, F4/80+ macrophages accumulated into the colon lamina propria in excess, and levels of Il‐1β and Tnf transcripts increased and Foxp3+ Treg were fewer. Our results indicate that pDCs control inflammation in the gut during C. rodentium infection and that they have an important immune regulatory role in colon‐draining lymph nodes.