Allergen-specific immunotherapy for allergic rhinitis: A new insight into its clinical efficacy and mechanism

Immunotherapy has been used widely for allergic diseases for more than 10 y ears but, in the opinion of many physicians, it is still a controversial fo rm of treatment. The exact mechanism of action of immunotherapy remains to be determined. In the present study, we review the clinical efficacy and me chanism of action of immunotherapy For allergic rhinitis. Recent double-bli nd placebo-controlled studies have demonstrated the clinical efficacy of im munotherapy for allergic rhinitis. This therapeutic method has several adva ntages over conventional pharmacological treatment. Immunotherapy is inferi or to pharmacological treatment in the short term, but in the long term it is substantially superior with respect to clinical efficacy. Immunotherapy has the potential permanently to alleviate the abnormal immunological respo nses of allergic rhinitis and to cure the nasal symptoms in the long term, even after discontinuation of injections. In addition, immunotherapy can pr event the onset of new sensitizations in allergic patients and may prevent the progression of rhinitis to asthma. It map therefore be possible for imm unotherapy to alter the natural history of allergic sensitization and its c linical manifestation. These lines of clinical evidence could affect strate gies of long-term therapy for allergic rhinitis. Modern molecular biologica l techniques have suggested that immunotherapy map affect allergen-induced TH responses or cytokine profiles, but there is no general agreement among investigators. However, IL-5 is likely to be the most important cytokine in volved in the clinical efficacy of immunotherapy, and the suppression of al lergen-induced IL-5 synthesis is most likely to be involved in the mechanis m of immunotherapy. Our recent investigations, focusing on specific IgE and IgG4 responses, suggest that immunotherapy-induced changes in these specif ic antibodies play a clinical role and are involved in the mechanism of act ion of immunotherapy. It is probable that immunotherapy modulates and affec ts many different immunological and non-immunological phenomena to produce clinical efficacy and that clinical improvement is a consequence of differe nt mechanisms over lime.