Far from always being adversaries, microbes and the immune system are often allies. Yasmine Belkaïd, an immunologist and the director of the Pasteur Institute since 2024, researches the continuous dialogue between them.

For a long time, the immune system was thought of as an attack mechanism. But that view then begged the question: how could the viruses and bacteria present in our bodies evade it? The immune system does more than fight microbes. It communicates with them and can even choose to stand down if a microbe is beneficial, for example. It is a global control system that restores disturbed balance. This essential function can only be fulfilled because the microbiome is there to stimulate, regulate, and amplify the responses of the immune system.