Measurement of Cytokines in Induced Sputum: Application to the Investigation of Asthma and COPD

Cytokines are important mediators of the persistent cycle of inflammation and repair that characterizes chronic airway diseases such as asthma, chronic obstructive pulmonary disease (COPD), and cystic fibrosis (CF). Interleukin (IL)-5 is a key mediator of the eosinophil infiltrate that characterizes asthma, whereas IL-8 is a potent chemoattractant for neutrophils in COPD and CF. IL-5 and IL-8 can be measured in airway samples obtained by the relatively noninvasive technique of sputum induction. Procedures for sputum induction have recently been standardized, and samples of airway secretions can now be obtained from most adults and children over 7 years of age. Sputum is induced via inhalation of hypertonic saline (4.5%) and assisted expectoration (
1
). The measurement of cytokines in induced sputum allows a direct estimation of the airway levels of these mediators in health and disease. This chapter details methods that have successfully been applied to the immunochemical assay of IL-5 and IL-8 in induced sputum.