The symbiotic microbiota represses the development of allergic inflammation, but the mechanisms involved are unclear. We have shown that intestinal bacteria induce the generation of type 3 T cells (Th17 cells and associated Tregs) that directly regulate pro-allergic type 2 T cells. In the absence of type 3 T cells, anti-helminth, but also pro-allergic responses, are exacerbated. Furthermore, the absence of microbiota during weaning has similar consequences on the deregulation of the immune system that last until adulthood, a phenomenon we name “imprinting”. We propose a model of the immune system where different types of competing and mutually suppressive responses establish a healthy equilibrium. When this equilibrium is lost, because of an absence of one type of microbe in the environment, inflammatory pathology develops. Therapeutic strategies can be designed with the aim to restore immune equilibrium to counter immunopathology.
Microenvironment & Immunity Unit, INSERM U1224,
Department of Immunology, Institut Pasteur, Paris
Invité par Michel Chignard.