HOMELECTURES > Satoshi Hayakawa M.D., Ph.D.
Sex, immunity and Evolution.
Satoshi Hayakawa M.D., Ph.D.
Satoshi Hayakawa M.D., Ph.D.

It was18 Oct 1980, I encountered the late Dr. Susumu Ohno, who later became my lifelong mentor. At that time, I was a medical student with a vague interest in immunology and evolution. Dr Ohno gave us a special lecture on "Genetic mechanism and evolution of sex determination" in a pathology course when he came to Japan. Five years later, I was fortunate enough to be given the opportunity to work in his laboratory, where I followed the molecular evolution of the HY antigen, which was then considered to be the sex-determination factor. Although HY antigen was not a sex-determining factor, I was able to use several Y-chromosome-specific sequences identified at that time as markers for the molecular diagnosis of post-transfusion GVHD and for the identification of microchimerism in several autoimmune diseases including scleroderma. The late Dr. Takeshi Matsunaga (later he moved Sweden as an associate professor at Umeå University) taught me basic immunology at that time. I also appreciate Dr Robert Bruce Wallace who taught me basic molecular biology including newly developed manual PCR with 3 hot water bathes and Klenow’s fragment. After returning to Japan, I continued to collaborate with Dr. Matsunaga on the evolution of mucosal immunity, and identified the large granular lymphocytes, which have been reported by a French pathologist Weil as "Les Cellules Granuleuses des Muqueuses Intestinal et. Uterine" more than 100 years ago, to be extrathymic T cells and γδ T cells which suppressed excessive immune responses to food and fetal placental antigens. Later, their essential nature was found to be regulatory T cells. Furthermore, in addition to the endocrine environment, the bacterial flora was found to induce these specific mucosal immune cells. Interestingly, suppressive immune responses in acquired immunity and viviparity, the growth of the fetus in utero by the placenta, appear for the first time in cartilaginous fishes through two round whole genome duplications. From 2007, I became a chair and PI of my department, in where I am pleased to be able to pass on the pleasure of sciences to many young scientists - Dr.Ohno's grandchildren, more than 30 years after COH days, and 20 years after his passing.

Satoshi Hayakawa M.D., Ph.D.
Dr Hayakawa graduated Nihon University School of Medicine (NUSM) and received M.D. in 1983. After 2 years of residency at Nihon University Itabashi Hospital, he studied reproductive genetics and molecular immunology with the late Dr Susumu Ohno, Dr R. Bruce Wallace and the late Dr Takeshi Matsunaga at Beckman Research Institute of the City of Hope from 1985 to 1986. After coming back to Japan, he obtained PhD. from NUSM and had worked as a clinician in the department of Obstetrics, Gynecology and Pathology at NUSM as well as at the National Institute of Infectious Diseases.
In 2004, he became associate professor of infectious disease control, then promoted to full professor in 2007. Dr. Hayakawa has a wide range of research themes such as mucosal immunity in female reproductive organs and possible roles of bacterial flora, cancer immunology, evolutionary medicine as well as pathography of famous musicians and artists. For the first time, he discovered extrathymic T cell differentiation in human decidual tissues and characterized their regulatory nature. He also reported an association between genetic polymorphism in TCR repertoire and susceptibility to inflammatory bowel diseases. He disproved an established theory of Th2 predominance in mammalian pregnancy. For the past ten years, he is concentrated the research focusing on mechanisms of vertical viral transmission including HIV, ZKV and SARS-CoV2 as well as involvement of local immune systems.