First reactions. Telephone interview, October 2025

“I believe this will encourage immunologists and physicians to apply the Tregs to treat various immunological diseases”

Shimon Sakaguchi, 2025 Nobel Prize laureate in physiology or medicine, has always been driven by the desire to find new ways to combat disease. In this conversation with the Nobel Prize’s Adam Smith, recorded just after the prize announcement, Sakaguchi speaks briefly about his surprise at the news and reflects on the fundamental research question that kept him dedicated to the field after many others abandoned it, a question that took over two decades to answer.

Interview transcript

Adam Smith: Hello, am I speaking with Shimon Sakaguchi?

Shimon Sakaguchi: Yes, it is he speaking.

AS: Hello, my name is Adam Smith. I think Thomas Perlmann may have mentioned that I would be calling.

SS: Yes, I have been expecting the call, yes.

AS: Thank you very much. First of all, many congratulations on the news of the award of the Nobel Prize.

SS: Thank you so much.

AS: You’re in Japan, so I imagine the news reached you when you were in your office at work?

SS: Yes, I have just come back from a conference and then I received this surprise. So, I’m very much elated.

AS: I can imagine. What was your first thought when you heard the news?

SS: It was a kind of a pleasant surprise, and I’m very pleased that our contribution to immunology, especially immunological tolerance was recognised. I’m very much pleased.

AS: I think that’s enough for the first moment, isn’t it? Simply just to be pleased.

SS: Yes, every year, my colleagues, they always say you might have a surprise, but I always responded that someday, when what we are doing contributes a real treatment in the clinic, that may then be somehow appreciated, but until then we must continue working on our research with the hope that it can be applied to the clinic.

AS: It’s been such a long story, hasn’t it? That I mean, right from Paul Ehrlich back in 1901, people have been thinking that there must be some regulatory mechanism that allows self to be separated from non-self in the body. And you, in particular, had the dedication for a long time to continue the search when others had given up, just for the cells that might regulate this. What gave you the, if you like, the dedication, the perseverance, to continue with the search when many others had left the field?

SS: Whatever other immunologists might think, the finding that normal T cells can suppress a disease development, that is always I can come back to. So every time a new idea or theory appeared, we checked which one is better, our idea or theirs. Then always we thought that, I thought that well, ours, at least, it can explain what we saw. That was the main motivation for why I could continue that research.

AS: Yes, it’s beautiful to see the way that discoveries can link people up in unexpected ways or expected ways, but it’s …

SS: Yes, the many immunologists and molecular biologists, one by one, they make it clear how it works and then, approaching to a clinical application. That’s really exciting and in this field. Yes. So in a sense, science is the collective efforts of the time. I’m happy that we can contribute from the beginning of this peripheral tolerance, regulatory T-cells-dependent peripheral tolerance. Then I could anyway continue to this day, this research. I’m becoming old, now it’s really my pleasure, yes.

AS: May I ask you what you think this Nobel Prize means for the field of immunology?

SS: Well, I believe that this will encourage immunologists and then physicians to apply the Tregs to treat the area of immunological diseases, control cancer immunity, or transplantation, or better or safer organ transplantation to prevent organ rejection. So that kind of the extension, that’s really we hope, and then if we can have a bit of contribution to that, the development, that would be very nice.

AS: Thank you very much. It’s a beautiful example of how science proceeds over a long course of time, deeper and deeper understanding of this beautiful system. It’s been an absolute delight to speak to you. It’s a great pleasure for me. Thank you very, very much indeed.

SS: You are very welcome.

AS: … and congratulations again on the lovely news.

SS: Thanks so much, it was nice talking to you. Bye bye now.

AS: Bye.

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