New Insights into the Molecular Basis of the House Dust Mite-Induced Allergic Response

House dust mite (HDM) represents world-wide one of the most common source of aeroallergens word-wide and more than 50% of allergic patients are sensitized to these allergenic molecules. Although the induction of specificTh2 cells as well as IgE by HDM is well understood, the events that control the initial Th2 polarization in response to HDM are still poorly defined. Notably, mechanisms by which HDM is recognized by the airway mucosa, interacts with barrier epithelial cells, leading to dendritic cell (DC) recruitment, activation, and subsequent Th2-mediated responses, remains to be elucidated. Moreover, whereas the allergenicity of the group 1 major mite allergens could be largely explained by their intrinsic proteolytic activity, the fundamental mechanistic question regarding the putative intrinsic allergenic properties of the group 2 major mite allergen remained unanswered to date. This review summarizes new insights into diverse determinants that contribute to the HDM allergenicity. In addition to the auto-adjuvant capacity of the two major mite allergen Der p 1 and 2, due to proteolytic activity and functional mimicry of the Toll-like receptor 4 (TLR4) co-receptor MD2 respectively, contaminating factors derived from HDM carriers, mainly endotoxins (LPS) et -glucans, are very important to activate the innate immune response which, in turns, is involved in the development of allergic response by HDM.