Allergen-specific immunotherapy: an update on immunological mechanisms of action

Specific immunotherapy (SIT) is the only treatment able to modify the natural history of the allergic subjects. Several aspects of the immunopathological response modified by SIT have been investigated; the first parameter historically studied was the production of allergen-specific antibodies. An increase of allergen-specific IgG4 and a decrease of IgE appear after SIT. A shift from Th2-polarized immune response toward Th1-oriented pattern has been reported after SIT. More recently, a crucial role for a subpopulation of T cells has been evidenced: T regulatory cells (Treg). Allergic patients have a defect of Tregs. SIT is able of inducing a specific Treg response. Sublingual immunotherapy is an alternative route of administration for SIT. Recent evidence shows that SLIT is also able of inducing a Treg response as detected by IL- 10 production.