Allergy is an immunologic disease displaying the distinctive features of the immune system: specificity and memory. Regardless of the clinical manifestation (i.e., rhinoconjunctivitis, rhinitis, asthma), the underlying immunologic disorder is based on the adverse reactions of cells in the immune system upon contact with allergens. These cells react with epitopes, structural parts of allergens, present in the allergenic source material. Two types of cells (i.e., T cells and B cells), produce receptor molecules (i.e., T-cell receptors and IgE antibodies, respectively) that by way of high-affinity interactions with the allergen, efficiently catalyze the presence of even minute amounts of allergens into clinical symptoms, the extreme consequence of which can be life threatening to the patient.

Allergens are molecules with the capacity to elicit IgE responses in humans. Inhalant allergens are proteins, readily soluble in water, found on airborne particles of a well-defined size. These characteristics are compatible with the concept that the particle carrying the allergen is inhaled and deposited on the mucosal surface, where it is solubilized. It can now stimulate the immune system, causing the production of specific IgE.

By this definition, any immunogenic protein (i.e., antigen) in the allergenic source material has allergenic potential. Even though most allergic patients have IgE specific for a relatively limited number of “major” allergens,<sup>21 King T.P., Hoffman D., Løwenstein H. , et al. Allergen nomenclature J Allergy Clin Immunol 1995 ;  96 : 5

Cliquez ici pour aller à la section Références</sup> when larger numbers of patients are investigated, still more proteins are found to be IgE binding. Thus, the number of allergens in a given source material converge toward the total number of antigens, and any antigen has the potential to elicit an IgE response.

Aqueous extraction of organic source materials is an old and well-established pharmaceutical technique; however, the procedures to obtain and control vaccines that retain all potential allergens and exclude irrelevant materials under conditions that preserve biologic activity are not straightforward and require standardization. The aim of standardization is the securing of batch-to-batch consistency; however, standardization gradually improves with the implementation of new technology. Contemporary standardization of an allergen vaccine as a minimum requires assessment of the following three aspects: (1) securing optimal complexity, (2) controlling individual major allergens, and (3) reproducing overall allergenic potency.

This article describes the procedures used to select source materials and for the preparation and standardization of allergen vaccines.