It has been our premise that the content of free (unconjugated) D/I occurs as a result of elastase activity in neutrophils and macrophages in blood and tissues, which can degrade elastin fragments prior to excretion in urine and therefore may be an indication of stimulation of neutrophils and macrophages by a heightened inflammatory state of patients with COPD as indicated by increased inflammatory markers detected in COPD [20,21]. This evidence concerns the gene ELN and chronic obstructive pulmonary disease.