Inflammation: a two-edged sword--the model of bronchiectasis.

A short-lived, controlled inflammatory response by the host is required to protect against incursions by foreign material into the upper and lower respiratory tract. If this response fails to eliminate the aggressor, inflammation is amplified and becomes chronic in an attempt to rectify the situation. This unsuccessful response is poorly controlled and caused damage to surrounding normal tissue, leading to progressive disease. Hence, inflammation can be helpful or harmful--a two-edged sword. Chronic bronchial sepsis, of which bronchiectasis is an example, and chronic sinusitis display the hallmarks of this 'vicious circle' of host-mediated, inflammatory tissue damage and provide a useful model in man in which to ask questions, the answers to which provide valuable information about the pathogenesis of chronic inflammatory disease of the lung.