Co-stimulation by dendritic cells maintains the peripheral pool of Tregs

Many aspects of an immune response are regulated by dendritic cells (DCs). DCs play key proinflammatory roles by sensing microbial invaders and promoting the activation of innate immune cells such as NK cells. In addition, DCs are required for the initiation and maintenance of adaptive T-cell responses against invading pathogens. Moreover, DCs also fulfill important anti-inflammatory functions: they induce peripheral T-cell tolerance by silencing self-reactive T cells and supporting the homeostasis of regulatory T cells (Tregs). A study in this issue of the European Journal of Immunology reveals that CD80/CD86 expression on DCs contributes to the maintenance of the peripheral pool of Tregs. This Commentary discusses current findings on this topic, focusing on the role of DCs in the homeostatic control of Tregs and myeloid cells, and the potential consequences for T-cell activation.