Allergen immunotherapy in asthma: current status and future perspectives.

Allergen immunotherapy targets Th2 cells activated by specific allergens, which constitutes the basis of allergic disease. Therefore, this approach has therapeutic potential for a variety of allergic diseases, including asthma, and may modify their natural course. Immunotherapy results in systemic immunological changes to allergens, thereby providing clinical benefits in allergic asthma. For example, immunotherapy attenuates T-cell-mediated airway inflammation by down-modulating Th2 and inducing Th1 differentiation. In addition, immunotherapy induces regulatory T cells, which produce IL-10. Meta-analysis has demonstrated that allergen immunotherapy improves clinical symptoms and non-specific airway hyperresponsiveness in asthma, and decreases drug requirements. Clinical studies have supported the usefulness if immunotherapy in mild to moderate asthma cases, particularly in patients with concomitant rhinitis. Several promising novel approaches have emerged as future immunotherapeutic strategies for the treatment of asthma. Current pharmacotherapy, including inhalational corticosteroids, provides powerful anti-symptomatic benefits in asthma; however, pharmacotherapy cannot cure or modify the natural course of asthma. As immunotherapy targets the background immunological state in asthma, it is expected to lead to long-term amelioration or cure. It is hoped that the positioning of allergen immunotherapy as a treatment option will allow the comprehensive management of symptoms in allergic individuals, and the modification of disease course.