Mayo Clinic researchers clarify link between controversial white blood cell and asthma, other allergy ailments

Thursday, March 20, 2008

SCOTTSDALE, Ariz. –After 130 years of scientific debate, the role of eosinophils—a rare type of white blood cell commonly associated with allergy sufferers—is starting to become clearer as the result of studies by Mayo Clinic researchers in Scottsdale.

Writing in the current issue of the Journal of Experimental Medicine (JEM), James J. Lee, Ph.D., suggests that while rare, white blood cells called eosinophils have traditionally been blamed for tissue destruction caused by asthma and other allergy related illnesses, these cells now appear to be responsible for mobilizing the body's defense system.

"What makes this study unique is that we've defined a role for eosinophils that no one suspected before," said Dr. Lee, a researcher and Associate Professor in Mayo Clinic's Division of Pulmonary Medicine. "By using models to manipulate the many variables, we developed an alternative view that the primary function of eosinophils is not to be destructive, but rather to serve as regulators and controllers of the disease."

In a normal, healthy person, as few as 1 percent of all the body's white cells are eosinophils. In allergy sufferers such as asthmatics, however, the number is elevated and the eosinophils tend to accumulate in the area of the allergy (in the case of asthma – the lung). As a result, when doctors looked into the lungs of an asthmatic patient in the past, they observed two things: extensive tissue damage and an elevated number of eosinophils. The connection seemed obvious, and as a result, the core belief in medicine has traditionally been that eosinophils are the culprit in asthma and similar ailments.

"The problem is there was no real evidence," Dr. Lee said. "We studied many variables using models we could manipulate, and when we did, we realized the presence or absence of eosinophils was not directly contributing to the damage."

What actually happens, according to Dr. Lee and his team, is that very early in the development of an allergy, the body begins gathering eosinophils in the affected area. When enough are present, they summon T cells to direct the body's immune response. Dr. Lee's paper suggests T cells don't act until beckoned by eosinophils, the opposite of traditional thinking.

"This information gives us a better understanding of the whole process and a better understanding of why current therapies work as well as they do," says Dr. Lee, himself an asthma sufferer (as is his son). "This insight allows us to focus our research on finding better treatments and exploring different approaches."

JEM is a leading life sciences journal and is considered among the most selective biomedical publications in the world. First published in 1905, it focuses on innovative advances in medicine, especially in the fields of immunology, infectious diseases, inflammation, cancer and vascular biology.

More than 20 million people in the United States have asthma, according to government estimates, and each year 5,000 deaths are blamed on the disease.

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Mayo Clinic is the first and largest integrated, not-for-profit group practice in the world. As a leading academic medical center in the Southwest, Mayo Clinic focuses on providing specialty and surgical care in more than 65 disciplines at its outpatient facility in north Scottsdale and at Mayo Clinic Hospital. The 244-licensed bed hospital is located at 56th Street and Mayo Boulevard (north of Bell Road) in northeast Phoenix, and provides inpatient care to support the medical and surgical specialties of the clinic, which is located at 134th Street and Shea Boulevard in Scottsdale.

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About Mayo Clinic

Mayo Clinic is the first and largest integrated, not-for-profit group practice in the world. Doctors from every medical specialty work together to care for patients, joined by common systems and a philosophy of "the needs of the patient come first." More than 3,300 physicians, scientists and researchers and 46,000 allied health staff work at Mayo Clinic, which has sites in Rochester, Minn., Jacksonville, Fla., and Scottsdale/Phoenix, Ariz. Collectively, the three locations treat more than half a million people each year. To obtain the latest news releases from Mayo Clinic, go to www.mayoclinic.org/news. For information about research and education visit www.mayo.edu. MayoClinic.com is available as a resource for your health stories.