Decrease of IgE-dependent platelet activation in Hymenoptera hypersensitivity after specific rush desensitization.

A receptor for the Fc fragment of IgE on human platelets has been recently described, which mediated an IgE-dependent activation in the presence of specific allergen. We investigated the allergen-induced activation of platelets from patients with Hymenoptera hypersensitivity before and after specific rush desensitization. Nineteen patients with a history of anaphylactic reactions were included (15 sensitive to yellow-jacket and four to honey-bee venom), fourteen/nineteen having experienced severe life-threatening systemic reactions and 5/19 large local reactions. All showed positive skin tests and high values of specific IgE. By comparison to the baseline results obtained before desensitization, a significant decrease of platelet activation (76.8% inhibition) after rush desensitization was observed. In the case of two polysensitized patients, after Hymenoptera venom desensitization alone, platelets not only lost their reactivity to venom but also towards the other allergen. This modulation of the IgE-dependent platelet reactivity during desensitization offers therefore a new approach for the study of allergen-induced desensitization.