Live Imaging of Dendritic CellTreg Cell Interactions

The decision to launch an immune response is made during the interaction of helper T cells and regulatory T cells with dendritic cells. Recognition of antigen leads to formation of immunological synapses at the interface between the cells and to activation of the T cells. The length of interaction between the T cells and dendritic cells influences the functional outcome. We have shown that in the absence of proinflammatory stimuli, regulatory T cells and naive helper T cells interact differently with dendritic cells. Neuropilin-1, which is expressed by most regulatory T cells but not naive helper T cells, promotes prolonged interactions with immature dendritic cells, resulting in higher sensitivity to limiting amounts of antigen. We tracked T cell–dendritic cell interactions in real-time using time-lapse microscopy, assessed synapse formation by immunofluorescence, and measured regulatory T cell activation by dendritic cells using suppression assays.