The aim of this study is to investigate the mechanisms whereby leukocytes are recruited to the lung in chronic obstructive pulmonary disease (COPD) and cause tissue destruction. The hypothesis is that in COPD more leukocytes enter the lung and it is these cells that are responsible for the degradation of lung tissue. We, the researchers at Imperial College London, will isolate leukocytes from the blood of patients with COPD, healthy smokers and normal subjects and measure the movement of the leukocytes to chemoattractants. We will examine further, which cell surface receptors are responsible for this trafficking of cells. Furthermore, the differentiation of these cells in vitro will be compared with cells from healthy smokers and normal subjects. Specifically, the expression of enzymes that are responsible for tissue destruction and the cell surface receptors on these cells will be investigated. The objective is to identify the mechanisms whereby leukocytes from COPD patients behave differently to cells from healthy smokers and normal subjects with a view to identify novel targets for drug therapy.