Our immune system is essential for protecting ourselves from pathogens. On the other hand, our immune system sometimes hurts our selves and causes diseases, such as autoimmune disorder and allergy. In our laboratory, we are conducting basic research in the immune system and also conducting the research to develop new vaccines and drugs for infectious diseases and immune-related diseases. In the basic research, we have identified new molecules involved in antiviral immune responses and have investigated their roles and functions using knockout mice. In the research for development, we identified new biomarkers that predict the adverse reaction after vaccination. Recently, we are focusing on the role of extracellular vesicles in the immune system and immune-related diseases.