[IqE dependent hypersensitivity and allergic inflammation].

The development of the IgE-dependent inflammatory reaction is made of 3 successives phases. The initiation period is related to dendritic cells, present everywhere in peripheral tissues, able after maturation to migrate to the draining lymph-node and to present immunogenic peptides to the naïve T lymphocyte. After this first step of sensitization, in case of a new contact with allergens, the inflammatory phase is rapidly developing: mast cell activation, then massive influx of eosinophils, neutrophils and mononuclear phagocytes, all phenomenas under the control of different T-lymphocyte subpopulations: T-CD4+ cells with a pro-allergic Th2 profile but also newly identified T regulatory cells (Tr-1, T CD4+ CD25+). The third phase concerns the repair process or more often in case of repeated allergenic aggressions, a remodelling process such as observed in patients with severe allergic asthma. All these data have lead to reconsider our understanding of the allergic reaction. In fact allergy seems to result from an aberrant immune response to the environmental allergens, while the non-atopic subject, exposed to the same allergens will develop a natural tolerance.