Early cytoskeletal rearrangement during dendritic cell maturation enhances synapse formation and Ca+2, signaling in CD8+ T cells

The interplay between dendritic cells (DC) and T cells is a dynamic process critically depending on DC maturation. Ca2+, influx is one of the initial events occurring during DC/T cell contacts. To determine how DC maturation influences DC/T cell contacts, time-lapse video microscopy was established using TCR-transgenic CD8(+) T cells from P14 mice. DC maturation shifted DC/T cell contacts from short-lived interactions with transient Ca2+, influx in T cells to long-lasting interactions and sustained Ca2+, influx of 30 min and more. Follow-up of DC/T cell interactions after 2 h using confocal microscopy revealed that long-lasting Ca2+ responses in T cells were preferentially associated with the formation of an immunological synapse involving CD54 and H2-K-b at the DC/T cell interface. Such synapse formation preceded MHC or B7 up-regulation, since DC developed into potent Ca2+ stimulators 7 In after initiation of maturation. Instead, the enhanced capacity of 7 h-matured DC to induce sustained Ca2+ responses in CD8+ T cells is critically dependent on the polarization and rearrangement of the cytoskeleton, as shown by Clostridium difficile toxin B inhibitor experiments. These data indicate that already very early after receiving a maturation stimulus, DC display enhanced cytoskeletal activity resulting in the rapid formation of immunological synapses and effective CD8+ T cell stimulation.