[Molecular imaging and analysis of microclusters responsible for initiating T cell receptor signaling]

T cell receptors (TCR) are activated by a specific antigen and interact with other signaling molecules, such as kinases and adaptors. Aiming at analyzing precisely the dynamic process of T cell signaling, we used a combined system of a planar bilayer and TIRF microscopy. This system allowed us to observe the T cell activation process from the initial cell-bilayer contact (time 0). Our observation revealed that microclusters with TCR were generated at the initial contact to gather into central supramolecular cluster, the immunological synapse, which was believed to be responsible for T cell receptor signaling. Furthermore the microclusters were generated continuously at the periphery even at the sustained state and they migrated toward the central cluster. These results suggested the important role of microclusters in T cell activation.