Asthma Blood Link

By Jennifer Abney Anchor

One scientist is helping answer the question of why some people are more prone to asthma. Asthma Blood Link

Published: Wed, August 20, 2008 - 4:22 am Last Updated: Wed, August 20, 2008 - 5:51 am

Jennifer Abney

Asthma is a condition in which the tissues lining the airways are inflamed and hypersensitive. When exposed to a trigger, the muscles that surround the airways contract, squeezing and narrowing the air passages. Inside, the tissues become more inflamed and swollen, further reducing the size of the air tubes. Mucus production increases and creates clogs. Patients may experience wheezing, coughing, chest tightness and shortness of breath or breathing difficulty. In severe cases, the air passages close up enough to prevent the lungs from getting enough oxygen. A patient can lose consciousness and die.

According to the American Academy of Allergy, Asthma and Immunology, about 20 million Americans have asthma. Nine million of them are under 18. Each year, asthma leads to 24.5 million lost work days and 12.8 million missed school days. The condition causes about 5,000 deaths annually.

The Asthma-Allergy Link
More than 70 percent of asthma patients also have allergies. In these patients, exposure to the allergen can trigger an asthma attack. Some researchers believe a specific type of white blood cell, called an eosinophil, may play a role in asthma symptoms.

Eosinophils normally protect the body from parasites. However, they also accumulate in areas of the body affected by an allergic reaction (in the case of respiratory allergies, the airways). These white blood cells carry a toxin that is released to fight an invader. In the case of allergies, the body mistakenly perceives harmless substances as an invader and mounts an attack. In the lungs, the release of toxins by eosinophils may damage the lining of the airways, and contribute to the development of asthma.

James Lee, Ph.D., Researcher/Associate Professor at the Mayo Clinic in Scottsdale, AZ, says researchers have had a hard time figuring out the exact role of eosinophils in development of allergic asthma because the white blood cells only appear to play a minor role in the body’s immune system response. To study the problem more closely, Lee and his colleagues genetically engineered mice that produced no eosinophils. Then they induced asthma into the animals. The researchers found that asthma symptoms were less severe in mice that were bred without eosinophils. In addition, no side effects were seen from the lack of eosinophil production.

The researchers hope to eventually use their findings to create better treatments for human asthma patients. Lee says current asthma medications, like steroids, can have serious long-term side effects. So far, scientists haven’t been able to find a way to completely keep eosinophils out of the lungs. But they have been able to reduce the numbers of the cells in the airways. If future treatments could significantly reduce the number of eosinophils, patients may be able to limit the amount of medications they use and still maintain control over their asthma symptoms.

For general information on asthma:
American Academy of Allergy, Asthma and Immunology, http://www.aaaai.org
Asthma and Allergy Foundation of America, http://www.aafa.org
National Heart, Lung and Blood Institute, http://www.nhlbi.nih.gov