The purpose of this study is to determine whether a specific genetic factor influences the severity of asthma symptoms.

Asthma is one of the most common chronic diseases in the United States. It is well known that asthma susceptibility is inherited; however, it is unknown if asthma severity is heritable. Studies suggest that levels of interleukin-16 (IL-16) may influence asthma severity. This study will examine the role of differences in the control region of the IL-16 gene in a racially diverse group of asthmatics and nonasthmatics and will determine if the IL-16 gene control region is related to asthma severity.

Participants in this study will undergo lung function and blood tests; they will also complete a questionnaire about their respiratory health. Asthmatic participants will complete a severity-of-asthma questionnaire.

Inclusion Criteria for Asthmatic Participants:

• Diagnosis of asthma

Inclusion Criteria for Non-asthmatic Participants:

• No diagnosis of asthma

400 asthmatics and 200 non-asthmatic controls will be recruited. The 200 non-asthmatics will be matched for age, gender and ethnicity with the asthmatics in the more severe half of the severity distribution. The participants will be from minority populations (at least 30% African-American and at least 30% Hispanic) and generally of lower socioeconomic status.