[Milieu Interieur: defining a healthy immune response for a better understanding of diseases].

What all individuals have in common is that they are all different. Some of the greatest differences between any two individuals may be related to their immune responses. These differences may result in variable outcome to infection, disease severity and response to medical therapies. Differences in immune responses are partly resulting from evolutionary forces acting at the level of host genetics and may also be due to differences encountered through environment and lifestyle. Despite these well-known inter-individual differences, this inherent variability is rarely included in clinical approaches or drug development. The LabEx Milieu Interieur consortium was established in 2011 to better define these immune differences in a healthy population and identify their genetic and environmental determinants. Such an understanding is crucial to achieve the promise of precision medicine that will take into account an individual specific immune response to ensure that public health strategies capitalize on recent scientific progress.