Asthma is a very common childhood chronic illness and is generally more severe in African Americans. The investigators attempted to determine whether a specific immune marker is associated with lung function and asthma severity.

This study examined the relationship between Interleukin (IL)-13 from phytohemagglutinin-activated polymorphonuclear blood cells and asthma severity, lung function (measured as FEV1%), and total serum IgE levels in African American children with clinically diagnosed asthma

Inclusion Criteria:

• African-American race, born in the U.S.
• Age 8-15 years
• Clinical diagnosis of asthma
• Subject is able to understand and follow verbal instructions in English

Exclusion Criteria:

• Asthma exacerbation in the 4 weeks preceding the research visit
• Oral/IV steroid use in the 4 weeks preceding the research visit
• Upper or lower respiratory tract infection in the 4 weeks preceding the research visit
• Antibiotic use in the 4 weeks preceding the research visit
• Use of a short-acting bronchodilator during the 6 hours prior to spirometry (lung function testing)
• Use of a long-acting bronchodilator during the 12 hours prior to spirometry (lung function testing)

African-American children, ages 8 to 15 years, with clinically diagnosed asthma which had been stable for at least 4 weeks prior to enrollment in the study.