Plasmacytoid dendritic cells (pDC) are critical to antiviral defense because of their high production of type I IFNs; less is known regarding their functions in bacterial infection. Moreover, pDC are involved in immunomodulation. A stable pool of regulatory T cells (Treg) is crucial for maintaining immune homeostasis. However, interactions between pDC and Treg regarding the regulation of Treg homeostasis are understudied. By using BDCA2-DTR mice as a systemic pDC depletion model, we identified increased steady-state numbers of FoxP3(+) T cells with an effector Treg-like phenotype in lungs, liver, and spleen tissues. During sublethal, pulmonary Klebsiella pneumoniae infection, pDC deficiency also elevated respiratory FoxP3(+) T cell numbers. Additionally, the improvement in acute pneumonia survival until day 5 post infection was accompanied by impaired proinflammatory cytokine production. In contrast, pDC-depleted mice exhibited a delayed clinical recovery during the post-acute phase. Therefore, we assume that pDC act as immunomodulators supporting the rapid onset of immune response in a proinflammatory manner and regulate inflammation or tissue regeneration in the post-acute phase. In summary, pDC assist in FoxP3(+) T cell homeostasis and the regulation of Klebsiella-pneumonia progression.
- Lippitsch, A.
- Baal, N.
- Chukovetskyi, Y.
- Cunningham, S.
- Michel, G.
- Dietert, K.
- Gurtner, C.
- Gruber, A. D.
- Bein, G.
- Hackstein, H.
Keywords
- BDCA2-DTR mice
- Klebsiella pneumoniae
- bacterial infection
- immunomodulation
- inflammation
- regulatory T cells
