Chronic obstructive pulmonary disease (COPD) is the fourth most common cause of death and the only one of the common causes that is still rising. The main effects of the disease are the destruction and inflammation of lung tissue rendering breathing difficult. COPD has significant effects on the quality of life of sufferers and the disease is predicted to be the fifth most common cause of disability in the world by 2020. Patients with COPD are prone to periods of worsening disease symptoms, known as exacerbations, which are often caused by viral and bacterial infections of the lung and current vaccines appear to have little efficacy in limiting these exacerbations. The loss of lung function caused by infectious exacerbations is irreversible and patients who frequently exacerbate experience more rapid disease progression. Nontypeable Haemophilus influenzae (NTHi) is a major bacterial species that colonises the airways and causes exacerbations in COPD. With the development of more sensitive molecular techniques it has been possible to ascertain that it is the acquisition of new strains of NTHi that correlate strongly with exacerbations. However, not all patients with COPD have NTHi in their lungs and the question remains as to why some COPD patients are susceptible to such infections. This study aims to answer this question by comparing the airways of COPD patients who are colonized by NTHi and those who are not to analyse whether the levels of protective antibodies in the lungs and the function of the immune cells in the NTHi colonized airway are reduced. Moreover, we aim to correlate this reduction in immunity with areas of lung damage ascertained by high resolution computed tomography. The aim of this research is to better understand this apparent deficiency in airway immunity as this is likely to impact on vaccine efficacy in COPD.