[The intestinal microbiota and inflammatory bowel disease].

The intestine hosts a complex ecosystem of microbial communities. Experimental data suggests that the microbiota has metabolic functions that contribute to nutrient and energy recovery from non-digestible substrates. Moreover, microbial colonization is essential for the normal development of the immune system and therefore seems to influence homeostasis between environmental antigen load and immune response. In genetically-susceptible individuals, an imbalance may give rise to diseases of immune dysregulation, including chronic inflammatory bowel diseases, in which there is an exaggerated immune response to harmless microbial antigens. Despite the availability of new molecular technologies, the normal composition of the human intestinal microbiota remains unknown. In the next few years, the results of international projects designed to determine the precise impact of the microbiota in various physiological and pathological processes will hopefully lead to major advances.