On April 20, it was with very great sadness that the Institut Pasteur senior management team announced the death of Philippe Bousso, Inserm Research Director and Head of the Institut Pasteur's Dynamics of Immune Responses Unit, on April 17, 2026, at the age of 55.

Philippe était une figure scientifique respectée de tous. Internationalement reconnu et apprécié pour son expertise, Philippe a conduit des recherches de très haut niveau qui ont profondément marqué le domaine de l’immunologie, notamment grâce au développement d’approches innovantes d’imagerie fonctionnelle permettant d’étudier les réponses immunitaires in vivo. Sa compétence, sa rigueur et son sens du travail collectif s’accompagnaient d’une grande qualité relationnelle, marquée par sa disponibilité, sa simplicité et une constante bienveillance.

En effet, en plus d’être un chercheur d’exception, Philippe était aussi une personne d’une très grande élégance et simplicité. Il faisait l’unanimité auprès de ses collègues par son intégrité, son sens de la justice et la qualité de ses relations humaines. Pour beaucoup, il était bien plus qu’un scientifique de premier plan : un collègue de confiance et un soutien précieux, dont l’engagement et la présence laisseront une empreinte durable.

Yasmine Belkaid, President of the Institut Pasteur, declared:  « La disparition de Philippe est une terrible nouvelle qui affecte profondément la communauté pasteurienne. Nous perdons aujourd’hui un immense collègue, un très grand chercheur qui incarnait l’excellence et la rigueur de la science pasteurienne : une vision scientifique d’excellence mise au service d’un projet résolument humaniste. Mais nous perdons aussi une personne extraordinaire, qui nous a toutes et tous marqués, nous qui le côtoyions au quotidien, par sa simplicité, sa dignité et son humanité. À travers la disparition de Philippe, l’Institut Pasteur perd un modèle d’homme et de chercheur, qui inspirait un respect unanime et contribuait à faire vivre une culture généreuse, bienveillante et profondément élévatrice de la science. »  

The Institut Pasteur management team expressed sincere condolences to his family, loved ones and colleagues. A private funeral was held for only immediate family on April 24.

The Institut Pasteur management team continues to offer support to all staff within his unit and department at this very sad time and to help with this sudden loss by any means. Bereavement support is also provided by the Occupational Health and Prevention Department (SPST) to Philippe's team and all those in need.

Please find here a brief outline of Philippe’s career. 

The Scientific Affairs Division and the Department of Communications and Public Affairs, in conjunction with Philippe's unit and department, have collected testimonials from several friends and colleagues who wanted to convey their affection for him. You can read their messages below. An online condolence book has also been created by the family for anyone to leave a message. You can access it by clicking  here.

The Institut Pasteur will pay tribute to Philippe's memory, probably by organizing a scientific event to showcase his contribution and his collaborative work to advancing the field of immunology in recent years. Further details will be provided nearer the time.
 

Image

Image

Témoignages

"Philippe Bousso was a brilliant and gifted scientist, recognized by all those who worked with him and hugely respected within the close-knit community working on intravital imaging of the immune system. He was passionate about technical developments – equipment, software and molecules – and had a unique talent for designing tools and approaches that would provide answers to the scientific questions he was seeking to elucidate.
Throughout the thirty years he spent working with us, he impressed us with his rare intelligence and limitless curiosity, the remarkable elegance of his experimental models, and above all his gentleness and kindness.
He was so understated and generous that often we would come away from a discussion with him in his office, proud at ourselves for having come up with an idea that actually Philippe had planted in our mind.
He was ambitious for himself and above all for others, and was an amazing catalyst and driving force for all the successes of our laboratory. 
But among all his qualities, what we will miss the most is his endless patience and his exquisite sense of humor. We struggle to find the words to thank him for all he meant and all he gave to the fifty or so people who worked in his laboratory." 

Fabrice Lemaitre and Zacarias Garcia, 
Inserm research engineers who worked with Philippe from 1998 and in his laboratory from 2005

“Philippe Bousso was an excellent scientist and, for me, a role model for how to do science creatively and collaboratively. Philippe was also an excellent colleague. He was generous with his time, providing support for our immunology colleagues and representing our department within and outside the Institut. He always had a minute for me when I needed to talk and I am grateful to have had his support. I’m having trouble understanding that he will not be in the halls of Metchnikoff, in his office, or at the next immunology retreat. I’m deeply saddened by his death, but I'm even sadder for the people he left behind - those who will no longer have his guidance and the amazing experience of working with him, his colleagues, his friends, and his family.” 

Molly Ingersoll, Head of the Mucosal Inflammation and Immunity Unit

"When I arrived at the Institut Pasteur, every time I would introduce myself to a colleague as a department manager and mention that I worked for the Department of Immunology with Philippe, I always got the same reaction: "Philippe! Oh, you are lucky!". It is rare to meet someone like him who elicited a unanimous reaction – anyone lucky enough to work with him was invariably struck by his deep humanity and humility, his kindness and concern for others, his desire to be useful while allowing everyone to shine. He led the Institut Pasteur's community of immunologists for many years as department director, bringing his inimitable humor and generosity to the role and making the department a welcoming place, especially for youngsters. We will miss him, those who worked with him in the Metchnikoff building and on the wider campus. I will miss him."

Guillaume Frasca, Scientific Affairs Division

“He was so talented yet humble and discreet. He always had an infectious cheerfulness. He radiated a calm, positive energy that was much appreciated by those around him. He had a natural curiosity and generosity, and we could always count on him to listen and offer support. He was a great scientist, but above all a wonderful human being.”

Caroline Demangel, Head of the Immunobiology and Therapy Unit 
and Deputy Director of the Department of Immunology

"In my job, PhD students were rather like children and grandchildren – what a joy it was to see them grow and flourish!
At the time, in 1995, I was Head of the Molecular Biology of the Gene Unit (U277 Inserm). The title of the unit harked back to the early days of genetic engineering and became obsolete after the lab was reconverted to an immunology lab – albeit molecular immunology.
It was such a pleasure for me to see you arrive in the lab, brimming with intelligence, enthusiasm and cheerfulness. What a joy, my dear Philippe, to see you develop so remarkably quickly and successfully. 
When you arrived, you were full of promise – and you certainly lived up to that promise. You were exceptionally gifted but also full of humor and kindness. You soon learned to stand on your own two feet – so much so that before long, older colleagues started going to see you to talk things over and seek your opinion. 
You soon began producing research that was exceptionally advanced in conceptual and experimental terms. In 2000, your outstanding publications led to an excellent PhD thesis.
At the age of 30, you were already an extremely accomplished scientist. You had achieved virtually a scientific full house. You topped it off with a period in the United States, before retuning to Pasteur for a brilliant career. Yet you also had those human qualities that made you not just a scientist but a true man of science. 
We will miss your scientific capabilities.
But we will also miss your kindness, your generosity and your smile."

Philippe Kourilsky, Professor Emeritus at the Collège de France, 
Honorary President of the Institut Pasteur and Member of the French Academy of Sciences

"We will miss Philippe immensely, not just for his scientific talent but also for his wonderful human qualities. He was always even-tempered and showed remarkable calm and objectivity in all circumstances. His availability and listening ear, his ability to reassure and suggest solutions to both professional and personal problems, all point to a deep kindness that one rarely encounters.
His warm welcome, always laced with humor, made every discussion an enjoyable experience. He was imaginative, he brought people and teams together in pursuit of shared aims, and he created a real collective energy. He was also a great teacher.
He had a genuine affection for others, and it was reciprocal. It was a great pleasure to work alongside him.
I will remember him as a wonderfully kind director, and his intelligence, generosity and elegance in his interactions with others will remain etched in my memory."
 

Marie-Laure Goupil, former assistant in the Department of Immunology

"I am deeply saddened by Philippe's passing. It is difficult to sum up Philippe in a few words. I was lucky enough to work alongside him and admire him for several years. For a long time we organized joint laboratory meetings between his unit, Matthew Albert's unit and my unit. These were opportunities for fascinating discussions at the intersection of immunology and virology. His "in situ" video microscopic approaches were a thing of wonder to me. Philippe Bousso was highly intelligent, discreet, elegant, imaginative and studious, all at once, and he also had an infectious and subtle sense of humor. My thoughts are with his family and his team. His scientific legacy is already bearing fruit – he was able to instill in his team something of his characteristic originality and scientific excellence."

Olivier Schwartz, Head of the Virus and Immunity Unit

“I met Philippe Bousso fairly recently. At the time, Philippe was working with DARRI to set up research programs based on mechanisms of action he had identified, with the aim of developing applications for the treatment of certain cancers. 
It was first and foremost the extraordinary originality of the immunotherapy approaches envisioned by Philippe, as well as their elegance, that caught my attention. “Excellent project,” “great scientific quality,” “top research group” are just a few of the enthusiastic comments from his peers on some of his projects in which I had the chance to participate.
Philippe also paid close attention to his audience and took care to present his groundbreaking concepts clearly and simply. He steadfastly supported everyone who worked with him.
Through his scientific discoveries, Philippe Bousso, alongside his team, has opened up new avenues in immunotherapy that will guide the development of innovative treatments."

Corinne Sarrazin,  Patent Engineer in the
Department of Research Applications and Industrial Relations