Interleukin-9 as a possible therapeutic target in both asthma and chronic obstructive airways disease

Asthma and chronic obstructive pulmonary disease (COPD) are important causes of morbidity and mortality worldwide. Both asthma and COPD are characterized by airflow limitation but distinct differences occur in the pulmonary inflammatory responses in the two conditions. Treatment options for asthma and COPD are limited (especially so for COPD), and both are in need of novel therapeutic interventions. Interleukin-9 (IL-9) is a potential target for such a therapy. This Th2-type cytokine, is secreted by a number of different cell types, and has multiple effects on a wide range of cells within the lung. In this review we will summarize current knowledge about the immunobiology of IL-9 and discuss the role played by IL-9 in inflammation in both asthma and COPD, and its potential as a therapeutic target.