Neutrophil elastase is an enzyme produced by neutrophils, a type of white blood cell that plays a crucial role in the immune system. This enzyme helps break down proteins and is involved in the body's response to infection and inflammation. It targets harmful bacteria and helps to clear them from the body. However, excessive activity of neutrophil elastase can lead to tissue damage and contribute to various diseases, such as chronic obstructive pulmonary disease (COPD) and cystic fibrosis. In these conditions, the balance between neutrophil elastase and its inhibitors is disrupted, resulting in inflammation and lung damage.