The team Natural Barrier and Infectivity is interested in survival adaptation and pathogenesis of intracellular pathogens. Indeed, during evolution, the selection pressure exerted by pathogens has led to the diversification of complementary immune responses. Conversely, pathogens have evolved various means of evading or subverting host defenses. Innate immunity, the evolutionarily older defence system, provides immediate protection from infection. It refers to the first line of defence against pathogens and includes muco-cutaneous barriers, the complement system and involves various types of cells such as macrophages. Innate immunity involves pathogen- recognition systems, and the diversification of responses relies, together with environmental factors, on the combined genetic diversity of both host and pathogen. Using relevant experimental models of infection, our team aims to identify these genetic factors and understand their role in the modulation of innate immune response and consequently, in the outcome of infection. The results of these models can then be applied to the human pathology by comparative and functional genomics. In terms of public health, the identification of genes and pathways involved in these diseases would open the way for the development of new pharmacological tools. In addition, knowledge of allelic variations is important for understanding the process of co- evolution and their impact on medicine (predictive value, personalized medicine).