Dr. Nishikawa has studied the mechanisms by which the immunosuppressive network, including CD4+ regulatory T (Treg) cells, suppresses anti-tumor immune responses, and has also been developing therapeutic strategies to overcome these mechanisms. In particular, he found the typical phenotypes of effector T cells, which are important for anti-tumor immune responses, that are suppressed by Treg cells depending on the nature of the antigen (exhaust for non-self and anergy for self-antigens). These findings are extremely important for understanding not only tumor immunity, but also various immune responses such as autoimmunity, allergy, infection and transplantation. In addition, he has recently proposed a novel concept in the carcinogenic process in which genomic aberrations of cancer cells affect the immune response and establish an immunosuppressive network in the tumor microenvironment, and commits to develop immunogenomic precision medicine.