Tasuku Honjo Biography

Tasuku Honjo was born on January 27, 1942, in Kyoto Japan, less than a couple of months after the Second World War began in the Pacific region. His father worked at the Kyoto University Hospital as a surgeon and later served at Yamaguchi University Medical School in Ube City as the head of the Otorhinolaryngology Department.

Honjo attended Kyoto University and earned his M.D. degree from the Faculty of Medicine in 1966. During his tenure there, Honjo came under the tutelage of Yasutomi Nishizuka and Osamu Hayaishi under whose supervision he completed his Ph.D. degree in Medical Chemistry in 1975.

Honjo went to the US, and in 1971, he was hired as a postdoctoral fellow at the Department of Embryology at the Carnegie Institution of Washington in Baltimore. Following this stint till 1973, Honjo went to the National Institutes of Health (NIH) in Bethesda, Maryland. There he remained a fellow at the National Institute of Child Health and Human Development between 1973 and 1977 and studied and carried out research on the genetic basis for the immune response. He worked with American geneticist Philip Leder at the NIH. Starting from 1992, for several years, Honjo served as an NIH Fogarty Scholar in Residence.

Meanwhile, from 1974 to 1979, Honjo worked at the Faculty of Medicine, University of Tokyo as an assistant professor. Thereafter, he joined the Osaka University School of Medicine as a professor in the university’s Department of Genetics and served in that position till 1984. While there, he described the mechanism and established the basic conceptual framework of immunoglobulin class switching or class switch recombination (CSR). He elucidated rearrangement of antibody gene in class switch by demonstrating a model. He then verified its validity by describing its DNA structure between 1980 and 1982.

In 1984, he was inducted as a professor in the Department of Medical Chemistry, Kyoto University Faculty of Medicine. He served in that position till 2005, and thereafter became a professor in the Department of Immunology and Genomic Medicine at Kyoto University Faculty of Medicine.

Meanwhile, he collaborated with Eva Severinson in cloning cytokines, which could enhance class switching and went on to discover IL-4 and IL-5, which were eventually identified to be critical for CSR, as also for T cell differentiation. After achieving success in cDNA cloning of IL-4 and IL-5, and interleukin-2 (IL-2) receptor alpha chain in 1986, Honjo went on to discover activation-induced cytidine deaminase (AID) in 2000. He demonstrated the importance of this 24 kDa enzyme in CSR as well as in somatic hypermutation (SHM) and showed that an AID-deficient animal lacked both CSR and SHM.

In 1992, Honjo and his colleagues at Kyoto University discovered and named the programmed cell death protein 1 or PD-1, a protein on the surface of T and B cells that they identified as an inducible gene on activated T-lymphocytes. They demonstrated in 1999 that the PD-1 knocked down mice were prone to suffer from autoimmune disease and thus deduced that the protein was a negative regulator of immune responses. Such findings contributed significantly to the development of cancer immunotherapy principle through PD-1 blockade and paved way for the development of anti-PD-1 cancer immunotherapies like pembrolizumab and nivolumab. Honjo received the 2018 Nobel Prize in Physiology or Medicine jointly with American immunologist James P Allison for his research. The two earlier received the first Tang Prize in Biopharmaceutical Science jointly in 2014 for identifying CTLA-4 and PD-1 as immune inhibitory molecules and discovering cancer therapy by inhibition of negative immune regulation.

A member of the Japanese Society for Immunology, Honjo served as its president from 1999 to 2000. In 2001, Honjo became a foreign associate of the United States non-profit, non-governmental organization called the National Academy of Sciences (NAS). In 2003, he became a member of German Academy of Natural Scientists Leopoldina, and in 2005 he was made a member of the Japan Academy.

From 2012 to 2017, he held office as President of Shizuoka Prefecture Public University Corporation. He became an honorary member of the American Association of Immunologists. He was appointed as Deputy Director-General and Distinguished Professor of Kyoto University Institute for Advanced Study (KUIAS) in 2017.

Over the years, Honjo has received several other major awards and honours for his work, including the Imperial Prize of the Japan Academy (1996), the Kyoto Prize in Basic Sciences (2016), and the Keio Medical Science Prize (2016).

A false claim did the rounds during the COVID-19 pandemic, claiming that Honjo believed the novel coronavirus was manufactured in a lab in Wuhan, China. The BBC Reality Check team later reported that Honjo issued a statement on the Kyoto University website saying he was 'greatly saddened' that his name was being used in spreading such 'false accusations and misinformation'.

Not much is known about personal life of Honjo except that he is married to a woman called Shigeko and his children include Hajime, a gastroenterologist, and Yasuko an embryologist.