An estimated 24 million Americans have asthma, a chronic, inflammatory lung disease characterized by breathing difficulties such as wheezing, coughing and shortness of breath.1 According to the latest research, an estimated 60 percent of people with asthma have allergic asthma.2 In some patients, exposure to allergens such as pet dander or dust mites can trigger an allergic reaction that can cause asthma signs and symptoms. These signs and symptoms of asthma include bronchial constriction, wheezing or tightening of the chest, coughing and increased airway obstruction.
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 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. When an allergic individual is re-exposed to an allergen, cross-linking to IgE bound on the mast cells may occur (see below).4
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.5,6
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 other approaches in asthma management that act early in the allergic cascade of events.
5 Fahy JV, Fleming HE, Wong HH, et al. The effect of an anti-IgE monoclonal antibody on the early- and late-phase responses to allergen inhalation in asthmatic subjects. Am J Respir Crit Care Med. 1997;155(6):1828-1834.
6 Delves PJ. Overview of Allergic Reactions. Merck Manual, Consumer Version. (November 2016). http://www.merckmanuals.com/home/immune-disorders/allergic-reactions-and-other-hypersensitivity-disorders/overview-of-allergic-reactions. Accessed November 11, 2016.