Approximately 20 million Americans suffer from asthma, a chronic, inflammatory lung disease characterized by breathing difficulties such as wheezing, coughing and shortness of breath.¹ According to the latest research, 10 million suffer specifically from allergic asthma.² In some patients, exposure to allergens such as animal dander, dust and mold spores can trigger an allergic reaction that can cause asthma signs and symptoms. These signs and symptoms of asthma include bronchial constriction (wheezing), coughing and increased airway obstruction.

IgE and the Allergic Cascade In some people, allergen exposure can cause a reaction known as the allergic response. This occurs when allergens are inhaled into the respiratory tract (nose, throat and lungs) and attach to the mucous membranes. These allergens are seen by the immune system as foreign invaders and an immune response is produced as the body prepares to fight them off. During this response, T-cells (a cell type of the immune system) send a signal to B-cells (B-lymphocytes) and stimulate production of IgE antibodies — a key protein involved in the allergic cascade.^3,4

IgE antibodies, specific to the allergen, are produced within a few weeks after exposure and released into the bloodstream. These IgE antibodies may attach to receptors on inflammatory cells such as mast cells. Unattached IgE antibodies remain free floating in the bloodstream.^5,6 When an allergic individual is re-exposed to an allergen, cross-linking to IgE bound on the mast cells may occur (see below).

When cross-linking occurs, mast cells release chemical mediators such as histamine, prostaglandins and leukotrienes (see below). These chemical mediators can cause inflammatory responses in the body. These inflammatory responses have been linked to asthma signs and symptoms such as bronchial constriction, coughing and wheezing.

Current asthma therapies generally treat the symptoms of asthma — decreasing ongoing inflammation and reducing bronchial constriction. Further understanding of the role of IgE has led to new approaches in asthma management that act early in the allergic cascade of events.

(1) Asthma Prevalence, Health Care Use, and Mortality, 2000-2001, National Center for Health Statistics, Centers for Disease Control and Prevention.

(2) National Institute of Environmental Health Sciences, Fact Sheet #9 "ASTHMA and its Environmental Triggers: Scientists Take a Practical New Look at a Familiar Illness." July 1997

(3) Allergy Principles and Practice. 3rd Edition, Vol. 1. Ed. Elliot Middleton. Moseby Publishers, 1988.

(4) The Merck Manual of Medical Information Home Edition, Merck Research Laboratories 1997.

(5) Taber's Cyclopedic Medical Dictionary, 16th Edition, F.A. Davis Company, 1989.

(6) Mayo Clinic Family Health Book. Ed. David E. Larson. William Morrow & Company, 1996.