Interview with the 2025 medicine laureate Shimon Sakaguchi on 6 December 2025 during Nobel Week in Stockholm, Sweden.

Tell us about your childhood 

Shimon Sakaguchi: I was born in Japan, in a rural area. I really enjoyed playing in nature. Always after school, we’d go out together with other kids until the sunset. We enjoyed playing in the river, just going up the hills. The place where I was born was facing the big lake, biggest lake in Japan, called Lake Biwa. We could swim there, just 15 minutes bicycling and we could go to the beach and mountains. So lots of nature. We liked that life. My father majored in Western philosophy at the university before World War II. He could speak French and English and other languages. Because of that, he was sent to the Indo-China and Vietnam when the war happened, because he could speak French. At that time, Vietnam was a French colony. Then he came back to Japan after World War II, and he decided to become a scholar in literature or philosophy. But at that time, it was so difficult to go back to university. So he decided to become a teacher in high school. He had lots of books and he was reading books for his kids, including me. There were so many books in our house, and I became familiar with reading books and various types, various fields. That was perhaps why I’m fond of reading books.  

What is your favourite book? 

Shimon Sakaguchi: I love some literature books written by Japanese novelists. When I became older, more philosophical books in science. For example, still, I like Jacob Bronowski’s book The Ascent of Man. I love his books. I recommend my student to read his books. 

Did your family background influence you? 

Shimon Sakaguchi: The family on my mother’s side, many generations they have been the village doctors, from the Samurai era, Shogun’s era. How many years ago? 200 years ago? We were very much accustomed to the lives of village doctors and when I was a kid, “Okay, that’s not so bad to become the village doctor too.” It was familiar to me how the village doctors treat patients. If the patient were poor, just some vegetables or something, that’s fine. That was the good old days.  

Before going to high school, I wanted to become an artist; painting or sculptures. I spent almost all my time in doing that. Then in high school, I must decide what to do, become an artist or something else. I realised that I’m not so talented as an artist. I said – the medical doctor was familiar to me – “Well, if I study hard, perhaps I can become a doctor.” I decided to go to medical school, and then I wanted to become a psychiatrist. Then I realised that I’m not so good at talking to other people, at talking to perhaps patients, so something else. I decided to become an immunologist, just studying the mechanism of disease, how to treat the disease. That may be better, more suitable for me. That was my decision. If I’m not so talented, I’ll become a village doctor. But I continued to the present day. 

What do you enjoy about science? 

Shimon Sakaguchi: I think there must be common elements between the humanities and the natural science. One thing I really like is the Leonardo da Vinci’s word “to see is to know”. Or is it, “to know is to see”? Anyway, for example, in art, the artists, they paint, and always I was interested in how he or she looked at the human figures or landscape in his or her own ways. Similarly, inside natural science, how we looked at the natural phenomenon events is still different from each among scientists. That is a kind of source of originality. 

How important is collaboration in science? 

Shimon Sakaguchi: If you become a scientist, then gradually you realise that, well, I must do that experiment and that experiment, but then I don’t have that expertise to know that. To get that knowledge I must collaborate with somebody. Some good words by perhaps a German philosopher (Georg Simmel), we need door and also bridge. Sometimes we must shut the door and just concentrate on what you think is important. Other times, you must open the door, and go over the bridge, to interact with other people. Two ways are always important. Just concentrate by shutting the door. Do something you think is important. Then other times you must communicate with other people. The two together we have some good progress in the understanding the nature. 

When I was young, and started my scientist career, you could go to the scientific meeting to discuss with other people. We’d just do experiments and then publish the paper and submit the abstract to the meeting. We didn’t go, just to save the travelling in cost. Then you become older and become more recognised, and then many scientific meetings I’ve been willing to join and have a discussion with them. I think at a certain stage as a scientist really you must concentrate on what you’re doing. Otherwise, you are influenced by the knowledge from others, who looks like a very modern knowledge or cutting edge knowledge. You will be sometimes disturbed. So sometimes it’s not so good. Concentrate on what is important and then communicate. Show them what you found, and then discuss with them and then go forward. That is the life of a scientist, I think. 

What’s your advice for young researchers? 

Shimon Sakaguchi: You must continue what you are interested in, whatever science. Just by continuing, you’ll discover something new. Continuation is important. Nowadays, there’s lots of new knowledge. Just open the internet and you’ll find something new. You may be influenced by that kind of knowledge and go, “Is this way or that way?” But just continue, then you’ll find something. Then you’ll become lucky. So continue, and don’t be so sensitive to stimuli from the outside.  You continue, and then you find something new. Whatever you are interested in, just start and continue. Your interest may change a bit, become more defined, and then you’ll find something new. You become more interested in what you are interested in.  

What qualities makes a successful scientist? 

Shimon Sakaguchi: First of all, you must be optimistic. The good scientists I know of, they’re all optimists. We will continue and we will find something new. That kind of motivation and driving force is important. 

Why is diversity important in science? 

Shimon Sakaguchi: Diversity is important because there is not only one way of looking at nature, like literature or human humanities. Even in science, you’ll see something from a different view. With different viewpoints, you can look at things very differently. That is a source of diversity. If there is only one way we’re looking at the nature or natural phenomenon, that is not good. Every science becomes kind of similar. We are conducting science because we can deal with it or treat it in a scientific way, but there are so many things not yet approached by modern scientific ways. So they are just left there. I hope that the young scientists will open new ways over looking at things, and then they’ll find something new. 

How did you learn about your Nobel Prize? 

Shimon Sakaguchi: Every year around the early October, many of my friends in Japan or in other countries, they send me emails, “Maybe this year!”, or something. But I’ve been accustomed to that kind of email. Then this year I had a call when I was in my office, and that was really a pleasant surprise. I was elated, and said: “That’s fantastic!” It was really a memorable day for me. Indeed, for two months I have been kind overwhelmed by various events. Interviews by many journalists and television broadcasts and I’ve been invited to give talks to various places. 

How does it feel to know your work has saved lives? 

Shimon Sakaguchi: We, in this field, of course we hope to contribute to clinical science and how to treat patients. After the announcement of the Nobel Prize, I have received so many emails from families and patients, and then they told me how his or her situation is and how his or her family members’ situation is. I really wish to say something to them, but always in science, we hope that science is progressing and we do believe that some day we can overcome these diseases and then we will find the way of treating the diseases. But at this stage, still we are studying. So always, I must say that I’m sorry I cannot say too good things. I mean, we are struggling to find out something good for treatment, but not yet. That’s sad, I must say that. But I really hope that after this prize, if we have more under more understanding from the societies and funding sources, and then facilitate the research and bring –  we are working on regulatory cells – so bring them to the clinic. That’s really a high hope. 

How did your home country react to your prize? 

Shimon Sakaguchi: Of course, the students in our university, they got excited. My family members and my friends from the high school days, so many people celebrated me to have had this prize. I have been asked what I think about the Japanese science and always I told them that conducting science is becoming more difficult than before in Japan. One reason is kind of depending on the economy. The size of the funding is almost the same as say, 20 years ago. So I told them, if you compare Japan with, say, United States or China, there’s a big difference in GDP. But if you compare with say, Germany, then the GDP is almost the same between Japan and Germany. Then you look at the immunology field, how much public support or governmental support, and in that, Japan is one third compared with Germany. I told the government and congress people, if you think that Japan should go on as kind of a technology or natural science, well, that kind of country that is emphasising technology to facilitate economy, then the current support is not enough, especially for young scientists. It’s very difficult for them to become independent. We need more support. I told journalists, and I visited the congress and I told them and the ministries for education. I visit there together with another laureate, Professor Kitagawa, Nobel Prize for Chemistry. So in just these two months, we have been doing those kinds of things in Japan. 

Watch the interview

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