Abstract
Immunotherapy (IT) using extracts of inhalant allergen has been used worldwide for
more than 75 years in the management of allergic respiratory disorders including asthma.
Good clinical results with IT depend on careful patient selection and the use of standardized,
high-quality extracts that have only become widely available in the last 20 years.
The immunologic and clinical consequences of effective IT include “desensitization”
of antigen-driven IgE-dependent mast cell activation, attenuation of specific T cell
responses, and down regulation of inflammatory cells and cytokines in the respiratory
mucosa, all leading to reduced end-organ responsiveness to the treatment allergens.
Many controlled clinical trials support the effectiveness of IT in reducing upper
airway symptoms and antihistamine use in allergic rhinoconjunctivitis. Effectiveness
in controlling symptoms of allergic asthma has been more difficult to demonstrate,
especially in multiply sensitive perennial asthmatics with moderate or severe disease.
The risk of fatal anaphylaxis from IT treatment in the United States is apparently
very low, but three quarters of these fatalities occur in asthmatic patients. Recent
evidence suggests that the risk is greatest and the benefit is minimal for perennial
persistent asthmatics requiring inhaled or oral steroids. Whether IT can be uniquely
helpful in preventing the emergence of allergic asthma in high-risk, atopic children
remains to be determined.
Key Words:
Immunotherapy - desensitization - allergens - allergic asthma - clinical trials
