Immune response is triggered upon antigen recognition by T cells through T cell receptor (TCR), and the activated T cells exhibit cell proliferation (clonal expansion) and functional differentiation, and effector function. Signal transduction through TCR upon antigen recognition regulates development, activation, and effector function of T cells through various signal transduction pathways. Our group is focusing on the analyses of molecular mechanism of signal regulation through TCR to induce such multiple functions of T cells, particularly activation and homeostasis. Major projects currently analyzing are: - TCR-mediated signaling and its regulation mechanism are analyzed through dynamic molecular assembly as TCR signalsome for activation. - Diversification of signaling pathways to induce different T cell function is analyzed particularly for TCR-mediated NF-κB activation. - The co-regulation of innate and acquired immunities is analyzed on molecules critical in innate immunity for adaptive responses. - Molecular mechanism of thymocyte development and selection is analyzed from the signaling point of view. These analyses are performed by employing new imaging tools at the single-cell and single-molecule level as well as in vivo gene-targeting technology. Our final goal is to develop immunological strategies by modulating signaling molecules to regulate hyper-responses of T cells such as allergy and autoimmune diseases, and immune suppression in cancer and transplantation.