Six weeks later, the above procedure will be repeated but with LPS stimulation. The subject will once again attend the hospital and lung function will be measured, blood and urine sampling will be performed. Subjects will inhale LPS (from Escherichia coli O26:B6, 50 μg; Sigma-Aldrich, St. Louis, MO) using a dosimeter. Bronchoscopy with BAL will be undertaken 6 hours following LPS inhalation. Prior to bronchoscopy, lung function will be measured in order to ensure that they may safely undergo LPS inhalation. At 24 hours subjects will return and lung function will be measured and blood sampling will be performed. The time points for BAL and plasma sampling are chosen to obtain insight into both cytokine/chemokine release and neutrophil recruitment after pulmonary delivery of LPS.