<qa>  What is the cause of COPD?Chronic obstructive pulmonary disease COPD is a worldwide chronic inflammatory disease of the airways linked to environmental exposure. The chronic course of COPD is often interrupted by acute exacerbations which have a major impact on the morbidity and mortality of COPD patients. A bacterial etiology for these exacerbations is common almost 50. Moreover, airway bacterial colonization linked to an increased susceptibility is observed in COPD patients. Effective Th17 immune response is needed to develop a good response against bacteria. Thus, this study aims to demonstrate that there is a defective IL-17 IL-22 response to bacteria in COPD leading to airway bacterial colonization and infection. 