CTSG and chronic obstructive pulmonary disease: Cathepsin G is a specialized neutrophilic polymorphonuclear leukocyte serine protease found in the azurophil granules and its function has been linked to pathogenesis of diseases associated with inflammation and neutrophil infiltration of the airways, such as bacterial COPD (Chronic Obstructive Pulmonary Disease) [43], [44], [45], [46], [47], [48].