The innate immune response is the first line of defense against infections. The innate immune system recognizes pathogens and
contributes to their elimination by a diversity of mechanisms. However, an excessive or dysregulated innate response can result in
tissue damage and cause pathology. Therefore, a delicate balance needs to be established between the activation and regulation of the
immune response in the context of infection.The innate immune system also plays critical roles in cancer initiation, development
and metastasis. Depending on the tumor microenvironment, the immune system can either contribute to the elimination of the tumor,
or support tumor growth. The molecular mechanisms that determine the anti-tumoralvs. tumor-supporting properties of the immune
system are still poorly understood.We use two complementary approaches to address these questions:1)	We use mouse models, which can
be easily manipulated genetically and experimentally in the laboratory, in order to understand the general principles that govern
the mammalian innate immune responsein vivo.2)	Mice and humans are separated by ~180 million years of divergent evolution. As a
consequence,major differences exist between the immune systems of these two species and frequently, knowledge gained from animal
studies cannot be directly translated in the human species. Furthermore, obvious practical and ethical barriers restrict
experimentation on human subjects in vivo. To circumvent these limitations, we developed novel models of mice repopulated with a functional
human immune system (so-called 'humanized mice'), which combine the advantage of a small animal model with the specificities of the
human species. Our work consists in (a) developing and characterizing improved models of humanized mice; and (b) using these models
to understand the cellular and molecular mechanisms of the human immune response to infection and cancer in vivo.