Immune regulation in idiopathic bronchiectasis.

Bronchiectasis is a complex pathological endpoint arrived at through a diverse interplay between lung infection and altered immune function. It comprises irreversible, abnormal dilatation of one or more bronchi, with chronic airway inflammation and is associated with recurrent chest infections, airflow obstruction, chronic cough, excessive sputum production, and malaise. Many pathogens are associated with this disease, including chronic bacterial infections, nontuberculous mycobacteria, and aspergillis. However, the etiology is poorly defined. Disease-associated genes indicate a likely contribution to disease mechanism both from innate and adaptive immunity. The role of immune mechanisms is highlighted by the occurrence of bronchiectasis in a subset of patients with rheumatoid arthritis or inflammatory bowel disease as well as diseases of immune dysregulation such as combined variable immune deficiency, transporter associated with antigen processing (TAP) deficiency syndrome, and hyper-IgE syndrome. Recent evidence indicates a possible role of excessive natural killer cell activation in pathogenesis.