Caractéristiques non allergéniques des allergènes

Allergens are capable of inducing specific IgE production and are recognized by IgE-receptor bearing cells, more particularly mast cells and basophils expressing FcɛRI, the high affinity IgE receptor. However, they are also capable of directly stimulating certain cells of the bronchial mucosa, especially in a protease-dependent way. For example, many allergens such as those from house dust mites (Dermatophagoides pteronyssinus et Dermatophagoides farinae) have protease activity which is involved in the activation of bronchial epithelial cells, dendritic cells, T lymphocytes, B cells, eosinophils and airway smooth muscle cells. Overall, these activations amplify Th2 polarization, recruitment and activation of inflammatory cells, and airway smooth muscle cell contraction. Receptors such as the protease-activated receptor (PAR) have been involved in these functions. PAR-2, which has a role in protease-dependent activation by many allergens, is over-expressed in bronchial biopsies from asthmatic patients. Both phenomena may be involved in the development and amplification of allergic asthma.