[From synthesis of immunoglobulins E to allergic syndromes]

Allergic reactions consist to a cascade of pathological events which are initiated by the activation of the immune system. These reactions result in a hypersensitivity state characterized by multiple parameters. Clinical symptoms among allergic population are characterized in a proportion of 75% of allergic individuals by a mechanism of immediate hypersensitivity, or IgE-dependent allergic reactions. Several conditions need to be met for the immediate hypersensitivity to occur: genetic background, the nature of allergens and the route of administration, the cytokine-dependent immunoregulatory mechanisms of IgE production, the threshold of reactivity of inflammatory cells, the amount of inflammatory mediators released, and the environmental factors. Therefore, the clinical expression of IgE dependent hypersensitivity results from a complex network of interactions between the host and its environment.